Annual Report 1961 - BEEP

MAURITIUS SUGAR INDUSTRYRESEARCHINSTITUTEANNUAL REPORT 1961Printed bv:CLAUDE MARRIER d'UNIENVILLETHE MAURITIUS PRINTING COY. LTD.37, Sir William Newton StreetPort Louis - Mauritius

CONTENTSPageMEMBERS EXECUTIVE BOARD AND RESEARCH ADVISORY COMMITTEESTAFF LISTREPORT OF CHAIRMAN EXECUTIVE BOARDREVENUE AND EXPENDITURE ACCOUNTRESEARCH ACTIVITIESINTRODUCTIONP. O. WieheCANE BREEDINGE. F. George & W. de Grootl. Arrowing2. Crossing3. Studies on seedling populations4. Selection5. Variety and Pre-release trials6. The release of varieties Ebene 50/47 and M.253/48NUTRITION AND SOILSl. Mineralogical composition of some local soils. D. H. Parish &S.M. Feillafe2. Improvements in leaf sampling technique for foliar diagnosis. P. Halais3. Comparative root studies of sugar cane varieties growing in differentsoil types. C. Mongelard & E. RochecousteCANE DISEASESI. General considerations2. Ratoon stunting disease3. Heat treatment of cuttings4. Chlorotic streak5. Red rot6. A method for inoculating leaf scald in field trials7. Gumming disease8. Fiji disease in MadagascarCANE PESTSl. The stalk borer2. The pink borer3. Army wormsR. AntoineR. AntoineR. AntoineR. AntoineC. RicaudC. RicaudR. AntoineR. Antoine1. R. WilliamsWEED CONTROLI. Herbicidal value of substituted ureas and triazine compounds inhumid and subhumid areas E. Rochecouste2. Evaluation of new herbicides3. Comparative effectiveness of Urox, Atratone, and DCMUCULTIVATION, ffiRIGATION, CLIMATE1. Comparative study of spray irrigation and surface"gravelly" and "free" soils2. Notes on climatic conditions of the 1961 crop yearirrigation onG. MazeryP. Halais3457935363940414345474851515354555556575962626365666771

SUGAR MANUFACTUREI. The performance of sugar factories in 19612. Two-boiling vis three-boiling systems1. D. de R. de Saint AntoineF. WieheE. C. Vignesyeasts in raw sugars3. Filterability of raw sugar4. Preliminary note on the presence of OsmophilicR. Antoinc, R. de Froberville & C. Ricaud5. Chemical Control Notes(a) Further studies on the use of the refractometer for routine(b)chemical controlF. Le Guen & M. RandabelThe determination of retention in vacuum filters1. D. de R. de Saint Antoine & E. C. Vignes6. Quality determination of cane in the factory 1. D. de R. de. Saint AntoineBY-PRODUCTS1. The composition of scums and heat coagulates from cane juice, inrelation to their nutritive value to animals D. H. Parish2. The extraction of cane juice protein and the assessment of its valueas a feeding stuff1. D. de R. de Saint Antoine &E. C. VignesAPPENDIXI. General description of sugar cane sectors11. Area under sugar cane 1956 - 1961Ill. Sugar Production 1956 - 1961IV. Yield of cane 1956 - 1961V. Sugar manufactured % cane 1956 - 1961VI. Sugar manufactured per arpent 1956 - 1961VII. Rainfall excesses and deficitsVIII. Wind velocityIX. Wind velocity, cyclone yearsX. Variety trend 1950 - 1961XI. Varietal composition of plantations 1957 - 1961XII. Relative production of virgin and ratoon canesXIII. Yield of virgin and ratoon canesXIV. Evolution of 1961 sugar cropXV. Weekly evolution of cane quality in 1961XVI. Weekly crushing rates 1948 - 1961XVII. Summary of chemical control data 1961(i) Cane crushed and sugar produced(ii) Cane, bagasse and juices ...(iii) Filter cake, syrup, pH, final molasses and sugar(iv) Massecuites(v) Milling work, sucrose losses and balance recoveriesXVIII.XIX.XX.XXI.Molasses production and utilisation 1948 - 1960Importation of fertilizersSales of herbicides 1960 - 1961List of crosses 1961.747880858689929710411IIIiiiivvvVIviiviiVlllixxxxixiiXIIIxivxvxviXVIIXVIIIxixxxxxiXXIIPhotograph on the cover is of the main buildings of the M.S.I.R.I. at Reduit,(Phot. C. Mongelard).

MEMBERS EXECUTIVE BOARDMr. Raymond Hein, o.c., Chairman, representing the Chamber of Agriculture.Mr. A. North-Coombes, O.B.E., representing Government, January to October.Mr. M. D. ffrench-MuIJen, representing Government, October to December.Mr Auguste HarelMr. L. de ChazalMr. G. S. de la HogueMr. Georges Rouillard, representing large planters. Acting Chairman, 16th July - 31st December.Mr. M. KisnahMr. S. Bunjun"1Jrepresenting small planters.MEMBERS RESEARCH ADVISORY COMMITTEEDr. P. O. Wiehe, C.B.E., Chairman.Mr. A. North-Coombes, O.B.E., representing the Department of Agriculture, January to October.Mr. M. D. ffrench-Mullen, representing the Department of Agriculture, October to December.Mr. A. dEmmerez de Charrnoy, M.B.E., representing the Extension Service of the Department ofAgriculture.Mr. G. P. Langlois, representing the Chamber of Agriculture.Mr. P. de L. d'Arifat "1~ representing the Societe de Technologie Agricole et Sucriere.Mr. A. Wiehe jand the senior staff of the Research Institute.

STAFFLISTDirectorAgronomistBotanistAsst. BotanistChemistSenior Asst. ChemistAsst. ChemistPlant BreederAsst. Plant BreederSenior Asst. Plant BreederGeneticistAsst. GeneticistPlant PathologistAsst. Plant PathologistSugar Technologist ...Associate Sugar TechnologistAssociate Chemist (S.T.)Asst. Chemist (S.T.)Asst. Sugar TechnologistAsst. Sugar TechnologistEntomologistChief Agriculturist ...Senior Field OfficerField Officers:HeadquartersNorthSouthLaboratory Assistants:ChemistryEntomologyFoliar DiagnosisSugar TechnologySecretary-AccountantAsst. Secretary-AccountantLibrarianDraughtsman-PhotographerClerks '"P. O. Wiehc, C.Il.E., D.Se., A.R.e.S., F.L.S.P. Halais, Dip. Agr. (Maur.)E. Rochecoustc, Ph. D., Dip. Agr. (Maur.)C. Mongelard, D.Se.D. H. Parish, D.Se., M. AgL (Q.U.D.), r.n.i.c.S. M. Fcillafe, Dip. AgL (Maur.)L. Ross, Dip. Agr. (MauL)W. de Groot, M.Se. (Wag. Holland)G. Harvais, D.Se. (Abenl.). (Resigned July 1961.)L. P. Noel, Dip. Agr. (Maur.) (as from 1.9.61) - i/c Belle RiveExperiment Station.E. F. George, D.Se., A.R.eS.J. A. Lalouette, Dip. Agr. (Maur.)R. Antoine, D.Se., A.R.es., Dip. AgL Se. (Cantab.), Dip. AgL (Maur.)C. Ricaud, D.Se., D.I.C.J. D. de R. de Saint Antoine, n.s., Dip. Agr. (Maur.)J. P. Larnusse, D.S. (Resigned on 28.2.61.)H. F. Wiehc, D.S., Dip. Agr. (Maur.) (as from 1.3.61.)E. C. Vignes, M.se., Dip. Agr. (Maur.)M. Randabel, Dip. AgL (Maur.)R. H. de Froberville, Dip. Agr. (Maur )F. Le Guen, D.Se.l. R. Williams, M.Se., D.I.C.G. Rouillard, Dip. Agr. (Maur.)G. Mazery, Dip. AgL (Maur.)P. R. Hermelin, Dip. AgL (MauL)-i/c Reduit Experiment StationA. Lagesse, Dip. AgL (Maur.), (Resigned May, 1961.)M. Mamet, Dip. Agr. (Maur.)R. Ng. Ying Sheung, Dip. Agr. (Maur.) (as from 1.7.61.)R. Bechet, Dip. Agr. (Maur.)-i/c Pamptemousses Experiment Station.F. Mayer, [lip. Agr, (Maur.)-i/c Union Park Experiment Station.L. C. FigonM. A. RajabaleeMrs. G. CaineL. Le GuenC. Cavalot (as from 1.7.61)P. G. de C. Du MeeM. M. d'UnienvilleA. lauffret (resigned 30.11.61)Miss M. Ly-Tio-Fane, D.A. (as from 1.12.61.)L. S. de RelandMrs. A. d'EspagnacMrs. A. BaissacMrs. J. DanjouxMrs. M. Rae

REPORT OF THE CHAIRMANEXECUTIVE BOARD 1961THE Board held 12 meetings during the year, two of which jointly with the ResearchAdvisory Committee. The only changes on the Board were Mr. G. S. de la Hoguewho replaced Mr. L. H. Garthwaite as representative of factory owners, and Mr. M. D.ffrench-Mullen who replaced Mr. Alfred North Coombes as Director of Agriculture in October.During my absence overseas, from July to December, Mr. Georges Rouillard acted as chairmanof the Board.We wish to place on record our appreciation of the services rendered by Mr. North Coombeswho has been serving on the Board on and off since May, 1954.ESTABLISHMENTThere were four resignations in 1961, the vacant posts being filled immediately viz:Mr. H. F. Wiehe replaced Mr. 1. P. Lamusse as Associate Sugar Technologist; Mr. R. Ng YingSheung succeeded to Mr. A. Lagesse as Field Officer while Mr. L. P. Noel was transferred fromhis function of Field Officer to that of Senior Assistant Plant Breeder to replace Mr. Harvais;Miss M. Ly-Tio-Fane was appointed Librarian in December to replace Mr. A. Jauffret. Mr. C. Cavalotwas appointed Laboratory Assistant in the Sugar Technology Division in July.Mr. F. Le Guen of the Sugar Technology Division returned to Mauritius on 4th July afterspending fifteen months study leave in England and obtaining a Diploma in Instrumentation.Dr. E. Rochecouste, our Botanist, must be sincerely congratulated on obtaining the Ph.D.degree of London University and it gives me great pleasure to do so.We are also pleased to note that Mr. D. H. Parish, our Chemist, has obtained the Fellowshipof the Royal Institute of Chemistry.Messrs. A. Wiehe and J. Maurice Paturau were re-appointed Consulting Sugar Technologists.BUILDINGSThe extension of the Biology wing to accommodate another laboratory for the Plant BreedingDivision is practically completed and terminates the Institute's main building programme as faras can be foreseen.As mentioned in last year's report, a house was built at Reduit and subsequently exchangedwith Government for another house.

SPECIALSTUDIES FUNDThe Special Studies Fund served to finance the studies of Messrs. f. Le Guen and de Reland,Thc former obtained the Post Graduate Diploma in Automatic Control at the NorthamptonCollege of Advanced Technology in London. while Mr. de Reland followed courses at the ByamShaw School of Drawing and Painting in London, at the Kew Herbarium and also received trainingfrom Messrs. Lcitz in Germany.FINANCEIt is heartening to note that the temporary increase in cess to Rs. 4.50 per ton of sugarproduced in 1961 has had the desired effect of re-establishing the Accumulated Funds of theInstitute at the level reached at the end of 1959. However, it will be noted that the cashavailable amounting to Rs. 266,000. will not be sufficient to finance the Institute until thereceipt in August of the first revenue from the 1962 crop.From an examination of the 1961 accounts and balance sheet it appears that the Institutehas reached a stage where further development cannot be envisaged with the present level ofrevenue. This creates a problem which will have to be carefully studied by my successor.I would also like to stress once again the fact that capital development, since the Institutestarted, has been carried out entirely from revenue and that it has not been possible up to nowto establish a cash reserve which could be used to tide the Institute over such difficult financialperiods.In closing this Report, I should like to express my gratitude to my friend Mr. GeorgesRouillard who kindly accepted to replace me as Chairman during my absence from the Colony,and to all my colleagues of the Board for their most valuable assistance.The staff is to be congratulated on its spirit of co-operation, and although it is now commonplaceto refer to our Director's able administration, I feel I should be failing in my dutyif I did not record my appreciation of his services.Chairman.25th January, 1962

REVENUE AND EXPENDffURE ACCOUNTYEAR ENDED 31st DECEMBER, 1961Running and Administrative ExpensesInterest paidDepreciation1,531,265.01 Cess on sugar exported44,949.61 Miscellaneous receipts112,224.981,688,439.60Excess of Revenue over Expenditure forthe year, carried to Accumulated Funds ... 632,654.85Rs. 2,321,094.452,250,876.8870,217.57Rs. 2,321,094.45BALANCESHEETAS AT 31st DECEMBER, 1961ACCUMULATED FUNDSREVENUE FUNDSSPECIAL STUDIES FUNDAIME DE SORNAY FOUNDATIONGROUND WATER RESEARCH FUNDLOAN FROM ANGLO MAURITIUSASSURANCE SOCIETY LTD.GOVERNMENT OF MAURITIUS(Purchase of Buildings)AIME DE SORNAY SCHOLARSHIP1,486,791.41 FIXED ASSETS (At cost less depreciationand amounts written off)64,227.46 Land and Buildings 1,697,535.69Equipment and Furniture:6,402.27 Laboratories, Houses &25,000.-Offices 46,245.05Agricultural Machinery &Vehicles 22,007.-353,502.43 1,765,787.74CURRENT ASSETS427,216.~Sundry Debtors 48,233.44Aim" de Sornay Foundation166,035.35 Account ...Cash at Bank and in...hand25,000.-92.50 (Ground Water Research FundAccount) 353,502.43Cash at Banks and in hand ... 336,743.81Rs. 2,529,267.42763,479.68Rs. 2,529,267.42AUDITORS' REPORTWe have examined the books and accounts of theInstitute for the year ended 31st December 1961, and haveobtained all the information and explanations we haverequired. In our opinion. proper books of accounts havebeen kept by the Institute so far as appears from ourexamination of those books, and the foregoing BalanceSheet is properly drawn up so as to exhibit a true andcorrect view of the state of the Institute's affairs as at31st December 1961, according to the best of our informationand the explanations given to us and as shownby the books and accounts of the Institute.(sd) P. ESPITALlER-NOEL J') Port Louis, (sd) P. R. C. Du MlOEBoard Members Mauritius, C.A.(S.A.), F.S.A.A.(sd) D. FFRENCH-MULLEN 25th January, 1962p.p. dc CHAZAL, DU MEE & Co.(sd) P.O. WIEHE Director Chartered Accountants,

INTRODUCTIONTH E act i v it i e s of the Sugar IndustryResearch Institute in 1961 are reviewedand summarized in this 9th AnnualReport.At the close of the year the staff numbered46, including six temporary junior assistants.Work in the various divisions progressed satisfactorilyalong the broad lines of an approvedresearch programme. Close contact was keptwith planters and producers and 1559 visitswere made to plantations and factories duringthe year. The Department of Agriculture beingthe responsible body for technical advice tosmall planters, useful discussions were heldwith the Director of Agriculture in order thathis extension officers may derive full benefitfrom the findings of specialists of this Institute.Rehabilitation of the four field stationsafter the 1960 cyclone was completed and caneproduction in 1961 was at a normal level totalling2285 tons as follows: Reduit 433, Pamplemousses713, Belle Rive 737, Union Park 402.THE 1961 SUGAR CROPThe area under sugar cane in 1961 was200,000 arpents of which 51 ~.~ was cultivatedby millers and 49 % by planters.A record weight of cane was harvested inspite of a severe drought which occurred duringthe first four months of the growing season.The setback caused by this dry period is reflectedin the cane elongation curve shown in fig. I.Late rains on the other hand prolonged growthand helped to produce a slightly greater weightof cane than would otherwise have been thecase. Climatic conditions prevailing in 1961are illustrated in fig. 2. Rainfall was deficientduring seven of the eight months of the growingseason and was significantly higher than normalduring the first two months of the maturationperiod. Both maximum and minimum temperatureswhich were above normal throughout theyear contributed markedly to the production ofmore cane during the vegetative period, butreduced the sucrose content of the caneduring the harvest season. It has been calculatedthat rainfall and temperatures have hadthe following quantitative effects on the productionof the island as a whole :Growing season, November 1960 - June 1961(a)shortage of cane dueto deficient rainfall: -3.9 tons/arpent(b) surplus of cane dueto higher temperatures: + 1.5 tons/arpentOverall effectMaturing season, July - October 1961(a) short fall on sugarmanufactured %cane due to excessrainfall: -0.61(b) short fall on sugarmanufactured %eane due to highermaximum and minimumtemperatures ~0.53Overall effect-2.4 tons/arpent-1.14

10-120110100QO80.;EV70'" ...J:o zW50observed that the yield of ratoon canes III 1961was well over average.As already indicated, conditions for canematurity were bad, and in fact were madeworse because the crop had to start early inorder to fulfil export contingencies. Fluctuationsin sucrose content from July to earlyDecember are shown in fig. 4, the highestaverage recorded being 13.92 in the north andthe lowest 11.65 in the south. Sugar manufactured% cane was 11.18 equivalent to 8.9 tonsGRO\"f1'~~fA\ONHA.RVE~THA~ON...J403020;'::% ·" " ·? ··"100IIn24·2D ATE,II103. 21Ẓ~"~~~~11Fig. I. Stalk elongation of sugar cane in 1961. Measurementat 8 sites distributed throughout theisland.'0It should be pointed out that these climaticeffects on growth and maturity were more orless pronounced in the different sectors. Thusthe coastal region in the isohyet of 50" sufferedproportionately more from drought, while normallyhigh-rainfall localities (above 100") benefitedfrom the reduced rainfall.The area harvested in 1961 was 93.2% ofcane lands. Of the weight of cane reaped,ratoons accounted for 85% of the crop. Yieldof canes ranged from 20.8 tons per arpent forplanters to 32.2 tons for estates; in the lattergroup, yields fluctuated from 25.3 to 40.3 tonsper arpent. Yields in virgins and ratoons in196\ are compared to those for the period1955-1959 in fig. 3, from which it may be8 I.o 0NOVbO oec. J...r-.ah, HII. .......ll. ,.p~ "'H Hill. HI

-11-Zlb"e, ~~J2<

-12-er +-20on TON$ C"NE lAP-PINTerIonon~ +-10o« c::w>-« 0CZ0Z0:;;:-10>wQ00'-20Fig. 5.~UG""...... NUF .. CTUMD io CANETONSSUG"l\/ ...RPENTVariation in cane and sugar yields in 1961 in different sectors of the island compared to the averageduring 1955 - 1959.THE CANE VARIETY POSITIONThe varietal composinon of the 1961 cropis shown diagrammatically in fig. 6, from whichthe following points of interest may be noted.Ebene 1/37 produced over a quarter of estatecanes ground for the island as a whole, thebulk of the production arising from the centralsector where growth conditions for this varietywere very near to the optimum. M.147/44 ""/"produced 21.5 % of the total, a proportionbelow that of 1960 and which reflects to someextent its intolerance to dry conditions. M.134/32 ""'/"has fallen to less than 20/~ of the canes groundfor the island as a whole, but it was still thedominant variety crushed in the western andnorthern sectors. Barbados varieties B. 3337 andB. 37172 together accounted for about the sameproportion as M. 134/32, B.3337 being importantin the centre and south and B. 37172 in allsectors except the centre.The approximate area under cultivation indifferent varieties in 1961 is given below,comparative figures for 1960 are shown inbrackets to indicate present trends in varieties.Fig. 6.Varietal composition of 1961 crop in differentsectors (estate - grown canes).o

-13-M.134/32M.147/44M.31/45M.202/46M.93/48M.253/48Ebene 1/37Ebene 50/47H.3337B.34104H.37172Others% area cultivated by estates19 (2~)22 (19)5 (5)2 (-)I (-)I (-)24 (25)1 (-)7 (6)2 (2)12 (10)4 (8)The composition of plantations made in1961 (fig. 7) shows that M.147/44 is the leadingvariety at present. Of 15,450 arpents planted,30 % was established under this variety reachinga maximum in the north (55 %) and a minimumin the centre (9 %). Ebene 1/37 occupied 13%of all plantations and was the dominant varietyplanted in the central plateau. Varieties whichoccupied more than 10% of the area planted in1961 are M.202/46 and M .93/48, while thoseoccupying between 5 and 10% included B.3337,B.37172 and Ebene 50/47.Deviations from the average yield of caneper arpent for all estates of the island has beencalculated with the following results and areillustrated in fig. 8....z~ 3Cl:"" Cl: 2w0.wz+1U""z'"ọ...-I'"z o 2...> "" 3woNN

~ 14-Maincharacteristics of commercial caneM .134j32M.147j44M.31j45M.202j46Year of release% Area cultivated in 1961 (t)193719 i-v-1956.,., J...-- i1956519592 IOptimum range of altitude and rainfal1 ...Subhumidto humid< 800' < 80'Subhumidto humid< 800' < 80'Humid300' -800'60'- 80'HumidHabitSemi-erectSemi-erect;tends to lodgeSemi-erectSemi-erectRatooning capacityGoodExcel1entFairGood?Relative stalk diameterMediumThinMediumThickRelative arrowingMediumShyVery shyHeavyTrashingFreeClingingFreeFreeRelative sucrose contentMediumLowHighMediumMaturityMedium-lateEarlyMedium-lateMediumFibre contentLowHighMediumMediumReactions to :Cyelone damageSusceptibleVeryresistantSusceptibleVerysusceptibleDrought ...VeryresistantModeratelyresistantVerysusceptibleResistantStalk borer (ProcerasSacchariphagus)ModeratelyresistantModeratelyresistantVerysusceptibleModeratelyresistantRatoon stunting diseaseHighlysusceptibleModeratelysusceptibleSusceptibleSusceptibleChlorotic streakSusceptibleSusceptibleSusceptibleSusceptibleRed rotModeratelysusceptibleResistantResistantResistantFiji disease (Madagascar)Very highlysusceptibleSusceptibleHighlyresistant?~----(0) Recommended for release.declining;-A.Iincreasing;no change.

-15-varieties cultivated in Mauritius in 1961.M.93/48M.253/48Ebene 1/37 Ebene 50/47 B.3337B.34104B.371721959(*)1951 (*) 195319561953.A-I24 - I ! 72 -12 =Humid tosuperhumidIrrigatedSuperhumid Humid Superhumid>800' > lOO'< 1200' > lOO'IrrigatedHumid< 400' < 80'Semi-erectSemi-erectSemi-erect;tends to lodgeErectErectSemi-erectErectGood?Good?FairGood?ExcellentFairFair to GoodThickThickThickMediumThinThinThinShyVery shyMediumFreeShyFreeShyFreeFreeFreeFreeClingingFreeFreeLowLowHighVery highLowMediumMediumMedium-lateLateMedium-lateEvenLateMediumMedium-lateHighVery lowLowMediumVery highHighVery highVeryresistantModeratelyresistantVerysusceptibleSusceptibleResistantModeratelyresistantResistantSusceptibleSusceptibleVerysusceptible?ResistantResistantModeratelyresistantModeratelysusceptibleModeratelysusceptibleSusceptibleModeratelyresistantResistantModeratelyresistantModeratelyresistantSusceptibleModeratelysusceptibleModeratelysusceptibleSusceptibleHighlysusceptibleModeratelysusceptibleHighlysusceptibleSusceptibleHighlysusceptibleHighlysusceptibleSusceptibleHighlysusceptibleSusceptibleSusceptibleResistantResistantModeratelyresistantSusceptibleResistantResistantResistant? ?Being tested? ? Moderatelysusceptible------~HighlysusceptibleHighlysusceptible

-17-the yield of the next best variety by 600 kgs,of a monetary value equivalent to Rs. 250 perarpent.M.31/45. Although nearly 5"u of the 1961crop was made up of this variety, M.31/45 hasan erratic performance and may be the causeof sad disillusionments if conditions do not fallexactly within its requirements, Apart fromthe fact that its extreme susceptibility to thestalk borer is notorious, M.31/45 is intolerantof any adverse growth factor. For these reasonsit is unlikely ever to occupy an importantfraction of the area under cultivation. On theother hand, M.31/45 has distinct qualities, includinghigh sucrose throughout the season. Theresults of eight final variety trials reaped in 1961have shown that its sucrose content was superiorto that of Ebene 1/37 and the yield of sucroseper arpent was the highest of the four varieties inthese experiments which also included M.147/44and B.37172. Finally, its paramount qualityis that it is the only commercial variety ofknown reaction grown in Mauritius which isimmune to Fiji disease.M.202/46 and M.93/48. These two varietiesare considered together because they werereleased in the same year and are being studiedconcurrently in trials and on estates. Both arevigorous and thick stalked, while they alsoratoon well and have juice of fair quality. Bothfind their optimum environment in the humidzone, but M. 202/46 appears to have a widerrange of tolerance extending from moderatelydry to fairly humid conditions. M. 93/48, onthe other hand, has produced sugar yields equivalentto Ebene 1/37 in the superhumid zone.It should be recalled that M. 202/46 tends toflower relatively profusely but in 1961 thischaracteristic was not apparent, as arrowing wasgenerally much below normal. Although highsugar yields, exceeding 6 tons per acre, were onrecord on several estates, it is doubtful whetherthese varieties will outyield M. 147/44 whcn plantedon a large scale. On the other hand, sinceboth varieties are much easier to cultivate andto harvest, it is conceivable that, on this scorealone, they will tend to displace M. 147/44 fromthe position it occupies at present.Attention should be drawn to the poorgerminating capacity of the variety M. 93/48under field conditions. Experiments are inprogress on the effect of different growth substanceson germination of cuttings of this variety.M. 253/48. The Canc Release Committeerecommended that this variety should be releasedfor commercial cultivation. The results of the1961 crop confirmed the opinion expressedpreviously that M. 253/48 is best suited toirrigated conditions. Exceptionally heavy yields(85 tons cane and 7 tons sugar per arpentfor 15 month-old virgins) were recorded onone estate. M. 253/48 is a thick-stalked, freetrashingvariety. Its main faults, comparedto present commercial varieties, are low sucrosecontent and low juice purity early in the seasonand is typically a late maturer. Its susceptibilityto chlorotic streak should also be emphasized.Since evidence has been obtained of therapid spread of this disease under irrigatedconditions, it is most important that cuttingsshould receive the short hot water treatmentbefore planting.Ebene 1/37. Little can be added to whathas already been written about this variety:susceptible to cyclones and chlorotic streak, it ishowever one of the highest sugar producingvarieties in elevated and humid regions, where itmay still be considered the standard cane.Approximately 812,000 tons of estate-grownEbene 1/37 were crushed during the crop whileapproximately the same acreage produced250,000 tons in the cyclone year of 1960.These figures indicate its outstanding powerof recovery.Ebene 50/47. Together with M. 253/48,the Cane Release Committee recommended tothe Board of Agriculture, Fisheries and NaturalResources, that Ebene 50/47 should be added tothe list of varieties approved for commercialcultivation. It is the second variety bred byHighlands S. E. which attains the rank of acommercial cane. Notes on its pedigree aregiven elsewhere in this report. The most noteworthyfeature of this variety is its high sucrosecontent throughout the harvest season and inthe different climatic zones in which it has beentested up to now. Few data are available as yet onits ratooning capacity. The information availableso far is inadequate to enable us to conclude underwhich conditions this variety performs best, but

.. 18··the indications are that it is best suited toregions receiving from 80 to 100 inches of rain perannum. Ebenc 50/47 is an erect, medium-stalked.free-trashing variety which may flower freely.It has greenish-yellow spiky leaves. It isresistant to gummosis and leaf scald but susceptibleto ratoon stunting disease, chloroticstreak, red stripe, eye spot and pokkah bccng,With regards to its sensitivity to the stalk borer, itappears to occupy an intermediate position betweenthe susceptible Ebene 1/37 and the resistantM. 147/44.B. 3337. This variety occupies 7 ~~ of thearea under cane. It is grown almost exclusivelyon inferior land of the superhumid regionswhere it has performed very well during thelast five years. It is possible that a competitorunder these conditions will be M. 93/48.B. 34104 is restricted to the irrigated areasof the west and is also grown on a fairly largescale in limited areas of the southem sector.The area cultivated under B. 34104 occupies 2 ~~of the total and has shown little fluctuationin recent years.B. 37172 occupies 12% of the cane area ofthe island and is grown on a fairly large scalein all sectors except the central plateau, whereit fails completely. Its juice quality is excellenteven late in the season. Fairly severe attacksof root disease in the subhumid area willprobably cause its decline in popularity.1961 was a year of low flowering intensity,in fact showing the lowest figure recorded since anannual survey was started several years ago.A small number of flowers, ideal from thepoint of view of commercial cultivation, renderedcrossing especially complicated. Despitethis major difficulty, 700 crosses were madeduring the year which yielded 105,000 seedlings.The number of different parents employed was108, a marked increase over previous years, andin line with the current policy of the Instituteof incorporating new parents into the breedingprogramme and evaluating the merits of theirprogenies.The transplanting of the young seedlingswas improved this year by the wider use ofpots made from very thin gauge polythene.Growth in these plastic pots was observed tobe superior to that in straw pots. Seedlingswere mainly transplanted in bunches and wereestablished at Reduit and Pamplemousses ExperimentStations, at F.U.E.L. and Britanniaestates.Investigational work of the Plant BreedingDivision centered chiefly on measurements ofprogenies in contrasting environments and onthe calculation of these results. Sufficientexperience has been gained in such work tosuggest suitable methods of evaluating thebreeding potential of new parent varieties.Factorial selection and progeny experimentswere started with this end in view. ExperimentsCANE BREEDING AND SELECTIONwere also continued on marcotting and crossingtechniques and a series of photoperiodic experimentsperformed in 1959 were repeated withcomparable success. The number of seedlingsand varieties now at various stages of selectionis summarised below. At stage (v) below, thesame variety is included in first selection trialsunder two environments: humid and superhumid.(i) Seedlings raised in 1961 forselection in 1962 and 1963 :(a) planted singly 9,287(b) No. of bunches of from7 to 10 seedlings initially... 10,774(ii) Seedlings raised in 1960 forselection in 1962 63,500(iii) Seedlings raised in 1959 and1960 now in bunch selectionplots to be selected in 1962and 1963. 5,044(iv) 1957, 1958, 1959 seedlings nowin propagation plots. 3,137(v) Varieties (1954 to 1958 series)in first selection trials. 482(vi) Varieties in multiplicationplots for planting trials on estatesin 1962 (1954-1957 series) 71(vii) Varieties in variety and prereleasetrials on estates:(a) M'46 to '57 series 113(b) Ebene 9(c) Foreign varieties 11 133

-19-In order to obtain early information on thepossi ble drought resistance of new varieties, twoobservation plots have been started at MonTresor and St. Antoine and include at presentabout 20 varieties.The results of variety and pro-release trialsarc reviewed elsewhere. Reference should bemade however to several varieties, some ofwhich had been mentioned in earlier reports:M. 305/49. The results obtained in 1961were not outstanding although this varietyperformed well in the humid area.M. 272/52 and M. 423/51. Both varietieshave produced better yields than Ebene 1/37 insuperhumid areas but were markedly inferiorto the standard variety, M. 147/44, in subhurnid,humid and irrigated localities. It appears alsothat M. 423/51 is susceptible to the stalk borer.M.409/51. This variety had shown promisein 1959. Its sucrose content is high, but it wiIIhave to be studied more closely in view of theinferior results obtained in two trials.M. 81/52. It is disappointing to recordthat this promising variety which performed wellso far, is susceptible to leaf scald. Its releasefor cultivation is therefore very doubtful.M. 13/53. Has given good results on irrigatedlands.M. 658/51. Promising for humid zone.R.397. This is the first Reunion variety tobe tested in Mauritius. It is thought from theresults of pro-release variety trials that it mayhave a useful place in subhumid areas. R.397flowers abundantly.N. Co, 310. This variety which is grown ona large scale in many sugar producing countriesis very disappointing under Mauritius conditionsand has performed particularly badlyin the superhumid zone.B. 41227, PR 1000. Both these varietieshave been included in trials under varying climaticconditions of the island but appear to beof no commercial interest.In order to diversify the genetical materialavailable for crossing and to extend furtherthe choice of commercial varieties, an intensiveprogramme of introductions from abroad wasdecided upon several years ago. The 48 canevarieties now undergoing quarantine will bereleased in March 1962, and it is hoped tostart another quarantine cycle a few monthslater.SOILS AND FERTILIZERSSoil Survey. The preliminary classificationof Mauritius soils was completed during theyear and the great soil groups mapped ona scale of I: 100,000. In this connection, thekind assistance received from the Department ofOverseas Survey, where the map is being printed,is gratefully acknowledged.The map shows the boundaries of the soilgroups, the 30 ~..~ slopes and the degree of rockinessand stoniness which, because of theirlocal importance, have been stressed by suitablemarkings.Twelve major mapping units are distinguished:low humic latosol, humic latosol,humic ferruginous latosol, latosolic reddishprairie, latosolic brown forest, dark magnesiumclays and grey hydromorphic clays, low humicgleys, mountain slope complexes, alluvial soils,lithosols and regosols, the only examples of thelatter in Mauritius being the calcareous sands.Work also progressed on the description ofsoil families within each great soil group.Mapping on the scale of I: 25,000 was alsostarted and fertility surveys were carried outby several estates whose chemists worked underthe supervision of the Chemist of the Instituteduring the intercrop period.The first results of mineralogical analyseshave been received from the RothamstedExperiment Station, England, and are presentedwith general comments in this report.Nitrogen. Conclusive evidence was presentedseveral years ago* that urea wasinferior to sulphate of ammonia as a nitrogensource for sugar cane when the fertilizerswere applied on the stool. As this is thenormal practice in Mauritius, it was recommendedthat planters should not use urea. It• Ann. Rep. M.S.I.R.l., 1959, 1960.

-20is gratifying to find confirmation of our workand recommendations from Jamaica and BritishGuiana, both countries having discouragedthe use of urea for sugar cane due to thepoor results obtained. However. because of thelow weight of urea per unit of nitrogen, it ischeap to transport and handle and i,; apotentially useful material. If its efficiencycould be improved. it could once again becomeof interest to the sugar industry.Experiments are in progress, therefore, inwhich attempts are being madc to improve theefficiency of urea by burying it in 'pochcs ' orwatering it on to the cane in dilute solutions,comparison with ammonium sulphate beingmade at the same time. Both fertilizers arebeing used at 30 and 60 Kgs N per arpent.It is too early yet to give any results of thiswork, but the experiments have amply confirmedprevious investigations which showedthat surface-applied urea compares unfavourablywith sulphate of ammonia as a nitrogen sourcefor cane.Three experiments were also laid downduring the year using sodium nitrate and ammoniumsulphate as nitrogen sources, the aim ofthe experiments being firstly to study the lossof nitrate through leaching and secondly toassess the extent of soil acidifying effects ofsulphate of ammonia when applied at heavyrates over several years.Phosphate. In view of the large quantitiesof rock phosphate now being used locallyand the fact that for the first time an alternativematerial to guano phosphate is on the market,work was started this year on the influence ofvarious factors which may affect the availabilityof rock phosphate. Subjects selected for studywere fineness of grinding, softness of the rockand the citric acid solubility. These investigationshave so far shown that although the preparationof guano phosphate leaves something to bedesired, there are no indications that the materialitself is inferior to any other form of rockphosphate.The effect on cane yields of form ofphosphate, that is, mono-calcic, tri-calcic andammonium phosphates, when applied on the trashor cane row has been studied fairly intensivelyand five experiments are still running. The experirnentsalthough giving erratic results for placement.show that significant yield responses canoften be obtained when phosphate is applied toratoon crops in fields deficient in this clement.Six trials were laid down to study thephosphate and calcium requirements of caneand possible interactions between these twonutrients.Potash. Many estates. on which foliardiagnosis had indicated a satisfactory level ofpotash, have reduced the rates of application ofthis element during one crop cycle to very lowlevels.It should be borne m mind that theamount of potash returned to a field in theform of molasses and potassic fertilizers shouldnot be allowed to fall much below the totalamount of potash removed from the soil. Thequantity of potash removed in millable stalksand in cane tops used for fodder can be assessedfairly accurately but. in addition, leaching lossesof unknown quantity occur. The rate of potashapplication even under conditions of high potassiumfertility should therefore remain at a fairlyhigh level.Studies on leaching losses are in progressand when the results of this work are knownmore specific recommendations concerning thelevel of potassic fertilization to be applied willbe made.Basalt. The results of experiments on basaltwere reviewed in the Annual Report of thisInstitute for 1958.Taking all the data then available, it wasfelt that the beneficial effect of basalt wasprobably due to physical effects althoughresearch on the subject was to be continued.Recent work appearing in the scientificliterature has shown that silica uptake andmanganese toxicity are closely interrelated. Ithad already been observed that one of theeffects of applying crushed basalt to our humicferruginous soils results in an increased uptakeof silica by the cane. A new line of researchhas thus been opened up which may possiblyexplain in part, at any rate, the marked improvementm yields following basalt dustapplication.If the value of one ton of cane at thefactory is taken at Rs. 30. an apparently per-

-21-manent benefit of approximately Rs. 90 per arpentper year follows the application of 100 tons ofbasalt powder to the humic ferruginous latosols.Before this practice can be generallyrecommended. however, information will haveto be obtained on the cost of producing andapplying the basalt dust at such high rates andon the effects of fineness of grinding. Possiblealternative ways of effecting this improvementin cane yield will also have to be studied.As it is essential, for both economic andscientific reasons, that as much information aspossible should be available on the application ofbasalt dust to the soils of the superhumid region,one new trial was therefore laid down in 1961,while further experiments are to start earlyin 1962.Foliar Diagnosis. The severe drought whichprevailed early in 1961 coincided with thegrand period of growth for sugar cane ratoons.The sampling of leaves could not therefore becarried out on the usual scale on either experimentalplots or sugar plantations. It is interestingto note that since 1947, when foliar diagnosiswas started on a large scale in Mauritius,sampling has been hindered by droughts ononly three occasions, namely: 1947, 1948 and1961. Furthermore there was practically noleaf sampling undertaken in 1960 on accountof the two cyclones.The number of leaf analysis made in 1961was as follows:Nutrients No. of leaf No. of detersamplesminationsNPK 2100 6300PK 4100 8200N 300 300Totals 6500 14800Two main improvements, which are describedin detail elsewhere, have been introducedfor the sampling of leaves of ratoon canesduring the critical hot and wet period extendingfrom the middle of December to the middleof April. The first is related to moisture conditionsand elongation of the cane in the threeweekperiod preceding leaf sampling, the secondis a correction factor for the age of the ratoonat the time of sampling.Germination in relation to potassic fertilization.Three experiments were carried out inorder to determine whether increased potassicfertilization of canes which are to be used asplanting material, has an effect on germinationof cuttings. Potash in the form of KCI wasapplied at rates of 0, 50, 100 kgs per arpent,one month and two months before the preparationof cuttings. Cuttings prepared from thosefields received the usual fungicidal treatmentbefore planting. Counts of germinated budswere made three months after planting, whiletotal growth of shoots was also measured. Nosignificant difference between treatments wasobserved.Root System Investigations. The developmentof root systems of different sugar canevarieties in different soil types was studied bythe excavation technique described by LEE.This consists in recording root dry weight inmeasured volumes of soil, and in this studyroot volume in the different soil layers wasalso determined. Investigations on the rootsystem of varieties M. 147/44 and Ebene 1/37were made in the following soil types: lowhumic latosol (Reduit, Pamplemousses), darkmagnesium clay (Magenta), humic ferruginouslatosol (Belle Rive) and latosolic brown forest(Union Park). Four excavations were madefor each variety in the respective soil type.From the data obtained with different varieties,a linear relationship was established betweenroot volume and root dry weight. It wasalso found that there could be appreciabledifferences in root development of the samevariety in different soil types. For example, inthe dark magnesium clay soil of Magenta, rootdevelopment was confined mostly to the firstfoot of soil below the surface, possibly becauseof the compact nature of this soil. Furtherinvestigations are in progress on this subject.

-~ 22--CANEDISEASESThe main pathological problems whichconfront the sugar industry of Mauritius "reratoon stunting disease and chlorotic streak,both of which undoubtedly reduce the overallsugar yield of the island. In consequence,emphasis continues to be given to these diseasesin the research programme.It is probable that root disease is also thecause of marked but insidious losses in yield,particularly when growth conditions are unfavourable.The screening of pathogenic soilfungi was therefore continued and 60 isolateshave been identified.Mention should be made here of two majorbacterial diseases, gurnmosis and leaf scald,which arc kept under control by the cultivationof resistant varieties. Much work, however,has to be done on these two diseases, not onlyin studying the reactions of promising varieties,but also in investigations of a more fundamentalnature on the variations of the pathogens. Theexistence of strains of different virulence ofthese organisms creates an additional problemin plant quarantine since it is now known, forexample, that host susceptibility and resistanceto gumming disease are not the same in Reunionand in Mauritius. In this connection, it shouldbe recalled that our primary line of defence inrelation to other diseases of major importance ­Fiji, downy mildew and mosaic, which do notoccur in the island - is through the quarantiningof cane varieties imported for breeding andother purposes. This primary line of defenceextends at present to Madagascar, where thepresence of Fij i disease on the cast coast is anever threatening menace to Mauritius. Closeco-operation continued during the year betweentheagricultural and research authorities in thatterritory and ourselves,Ratoon Stunting Disease, The res ults oftrials harvested during the year have shownaverage reductions in yield in virgins rangingfrom 11 % in Ebene 1/37 to 41 % in M. 202/46at Belle Rivc Experiment Station. Under drierconditions at Pamplemousses, losses have fluctuatedin ratoons from 7 % in B. 37172 to 20 %in B. 37161. These results confirm previousobservations that the disease is more seriousin suprrhumid than in humid areas.The long 110t water treatment installation atthe M.S.P.A. station at Belle Rivc worked belowits capacity and approximately 2500 tom ofcuttingswere t.cated. Good germination was obtainedearlier in the year but severe failures were alsoregistered and out of 375 arpcnts of nurseriesplanted, only 243 arpents were maintained toprovide healthy material for the 1962 plantations.The heat treatment of cuttings is regardedwith much disfavour in some quarters becauseof the poor germination which is sometimesexperienced. It should be emphasized oncemore, however, that the ratoon stunting diseaseproblem is still with us, and that appreciableimprovement in sugar yields could be achievedif healthy cuttings were used for all new plantations.A project is being studied for establishinga central nursery from which healthyplanting material would be available for secondarynurseries on estates.Chlorotic Streak. In spite of the short hotwater treatment, chlorotic streak remains theimportant disease of the superhumid zone andin some restricted areas of the subhurnid zoneassociated with certain soil factors. The substantiallosses in yield due to the disease havebeen demonstrated in the past and preliminaryexperiments have shown that it is likely thatthe disease is transmitted in the soil. In anattempt to elucidate factors involved In thetransmission of chlorotic streak, a carefullyplanned experiment is in progress at Belle Rive.Canes, initially healthy, are grown in insectproofcages containing sterilized soil free fromnematodes; the canes are subjected to a combinationof factors which have been designedto provide an explanation for some of the manyquestions which have to be solved as a preliminaryto a better control of the disease.Fiji Disease in Madagasear. Reactions ofcommercial canes important to Mauritius havebeen assessed in 1st ratoons in the first trialestablished at Brickaville in 1959, in co-operationwith the Institut de la Recherche Agronomiquede Madagascar as follows:

-23-Highly susceptibleSusceptibleModerately susceptible:Highly resistantM. 134/32, B.34104,B.37172M.147/44B. 3337. B.37161M.31/45.The variety M.112/34 is being tested in the2nd trial planted in July 1960. The experimenthas been harvested and results will be obtainedin 1st ratoons next year.M.202/46, M.93/48 and Ebene 1/37 are atpresent in the 3rd trial planted in December 1961and M.253/48 and Ebenc 50/47 are undergoingquarantine in Madagascar and will be includedin the 4th trial scheduled to be planted inNovember 1962.After the discovery of Fiji disease on theeast coast of Madagascar, one of the measuresadopted for the protection of neighbouringCANEApart from moth borers which as usualwere the most important pests during the year,attacks by thrips, scale insects and army wormsoccurred. The outbreak of thrips (Fulmekiolaserrata Kob.) was in the north and many fieldswere affected, some quite severely.Research was centered upon the stalk borer,Proceras sacchariphagus, and progress was madewith studies on the biology of the moth. Theobject of this work, which will be extendedlater to other aspects of the insect's activities,is to provide information upon such subjcets asthe reproductive capacities and habits of themoth and the nature of their association withsugar cane and its varieties. For example,the moths vary in size and egg-laying capacity,while cane variety may influence feeundicity byaffecting larval diet. Again, the insect appearsto be monophagous in Mauritius, attacking noother plant, and the reason for this lies presumablywith host-plant· stimuli which conditionadult behaviour.The most notable item of work in connectionwith the stalk borer was the introduction ofthe larval parasite, Diatraeophaga striatalisTowns., from Java. The parasite is the onlyTachinid fly known to attack Proceras sacchariphagusand, like its host, it is native to Javacountries was thc prohibition of the entry andsale of canes in the town of Tamatavc. Theauthorities in the province of Tamatave hadbeen pressing very hard for some time for thelifting of the prohibition. An agreement hasnow been reached whereby the entry and saleof cane in the town of Tarnatavc will beauthorized only after the setting up of a controlorganization whose duties have been defined.The measures recommended include the maintenanceof two inspection teams within the perimeterof the port of Tamatave, whose duty isto ensure that no part of the sugar cane plantis taken into that area. The Governments ofMauritius and Reunion have agreed to pay theexpenses involved.The co-operation of the Minister for Agriculturein Madagascar is once more gratefullyacknowledged.PESTSwhere it appears to be quite an importantnatural enemy of the borer. Several hundredflies were liberated in the north during June andJuly, but it is not known if the parasite hasbecome established, The insect is accordinglybeing reared in the laboratory in an effort toobtain more individuals for release in the field.This is the first time that the parasite has beenartificially reared.An assessment of the incidence of parasitesin Proceras larvae collected during the yearshowed that Apanteles j1avipes Cam. is theonly common larval parasite. Its incidence inborers collected varied from 0 to 50% and theinsect is evidently often of considerable valuein cane fields. However, the fact that onlyone larval parasite appears to exert any appreciablecontrol on the borer emphasizes theimportance attached to seeking other speciesabroad.The intensity of stalk borer attack on varietiesEbenc 50/47, M.202/46, M.93/48 and M.253/48was observed in commercial plantations and invariety trials. M. 202/46 seems to be the leastattacked by borers and in this respect comparesfavourably with M. 147/44. M.253/48, on theother hand, is probably the most susceptible ofthese varieties, with Ebene 50/47 and M.93/48

.- 24·-occupying intermediate positions.Other work during the year included theidentification of weeds which harbour the pinkborer (Sesamiai and experiments to clarify theeffect of army worm attack on young ratooncane.WEEDCONTROLSubstituted Ureas aud Triazine Compounds.Investigations on the herbicidal value of thesubstituted ureas and triazine compounds werecarried out in plant canes in the humid andsubhumid localities. These herbicides wereused alone and in combination with sodiumchlorate and TCA. All applications weremade in pro-emergence of the weeds, a weekafter planting, in fields receiving either surfaceor overhead irrigation. The substituted ureasand the triazine compounds gave generally comparableresults and the addition of TCA andsodium chlorate did not increase their efficacy.It must also be pointed out that these herbicidesdid not give satisfactory results consistentlyand that in some trials they did not provesuperior to the standard formulation used.Atratone, Urox. These herbicides weretested in pre-emergenee application in comparisonto DCM U at the two Experiment Stationsof the superhumid locality at dosage rates 4and 2.4 lb active material per acre. A weedsurvey made two months after spraying showedthat DCMU gave a better control of theweed population at both rates of application.New herbicides. For the evaluation of newherbicides the logarithmic spraying techniquewas used. The herbicides Thiuron, Dichloralurea and Prometone were evaluated withrespect to DCMU in pre-emergence treatment.From the data obtained DCMU was foundto give more satisfactory results. On the otherhand, Paraquat proved more effective thanPrometone in post-emergence of the weeds.It must be observed, however, that Paraquat atthe dosage rates used caused injury to the caneplant.IRRIGATIONThe irrigation experiment' started at McdineS.E. (Palmyre) in 1957 has now been pursuedduring four years and it is desirable at thisstage to give a brief account of the resultsobtained and to review the development ofoverhead irrigation in the island generally.In both the Iatosolic reddish prairie soils("gravelly") and the low humic latosols ("free"),there has been no significant difference in caneyields between fields irrigated by the standardsurface method and by overhead spray. Onthe other hand, water economy by spray irrigationhas been considerable. Indeed, the gravellysoils require such a large amount of water whenirrigated by surface that it is only under exceptionalcircumstances that this method can be used.It should be pointed out that during the course ofthis experiment, the limited equipment availabletogether with unavoidable irregularities in thewater supply, made it impossible to cope intime with the water requirements of the variousexperimental plots. As a consequence, it isprobable that yields lower than those whichwould otherwise have been obtained were recordedin some of the sprayed plots, particularly thoseon gravelly soils.The results which are summarized belowrepresent an average for the period 1958-1961(1960 excluded because of cyclone effects).Together with growth measurements and soilmoisture determinations, which were obtained atweekly intervals throughout the duration of theexperiment, they confirm the opinion that inthe subhumid zone of Mauritius, optimumresults should be obtained with 50" of water perannum applied at the rate of 2" to 3" perirrigation depending on type of soil and conditionof the land.• For a description of this experiment, see Ann. Rep. M.S.I. R.f., 1958, p. 8l.

-25-Average 1958-1961 (1960 excluded)Type of SoilLow humic latosol(free soils)Latosolic reddish prairie(gravelly soils)Type of irrigationOverhead(semipermanent)SurfaceOverhead(mobileequipment)SurfaceNumber irrigations per annum 1212II11Amount of water, inches, applied perarpent per annum 307228209Yield of cane, tons per arpent 37.638.829.128.9Cost of irrigation per annum:Rs, per arpent 21698275145Rs. per ton cane 5.742.269.455.00Apart from the basic information which thisseries of experiments has provided, it has helpedconsiderably in focussing the attention of planterson the possibilities of overhead irrigation.The mobile equipment used for irrigating gravellysoils will be transferred to another estatein 1962 in order to compare the merits andlimitations of overhead and surface irrigationson dark magnesium clay soils. The experimentson free soils will continue at Palmyre howeverand I should like once more to take this opportunityof expressing my gratitude to the Managerof Medine S. E. for his kind assistance.When the Palmyre experiments were startedin 1957, there was only one overhead irrigationinstallation in Mauritius to irrigate about 150arpents. At the end of 1961 a total area of3700 arpcnts was under spray irrigation asfollows: West 1150, North 700, East 1150,South 700. This area represents about 18% ofGROUNDThe electrical reSIStIVIty survey started in1960 by the Compagnie Generate de Geophysiqueat Plaines Wilhems, Black River, Flacq andGrand Port was completed early in the yearand the broad conclusions which these investigationshave revealed are summarized below.the total irrigated area. Several estates haveplans for a further extension of overhead irrigationwith semi-permanent installations.Another important contribution to thedevelopment of spray irrigation is undoubtedlythe introduction of the "Boom-O-Rain" sprayer.This machine, which has rotating arms with aspan of 140', is provided with devices forcompensating to some extent the adverse effectof wind on spray distribution. Its long rangerenders it highly suitable for use in sugar caneplantations because it eliminates the necessityof penetrating into the cane fields for placementof the sprinklers and facilitates night workconsiderably. The machine requires roadsspaced at intervals of 220'. This additionalcost, however. seems to be compensated by theincreased efficiency of the irrigation resultingfrom longer working hours and better waterdistribution.WATERThis work was extended later in the year tocover an approximate area of 120 sq. kms. atNouvelle Decouvcrtc, in the south east ofFlacq, Midlands and Chamarel.Meanwhile the programme of core sampling,bore hole drilling and pumping tests follow-

-25-Average 1958-1961 (1960 excluded)Type of SoilLow humic latosol(free soils)Latosolic reddish prame(gravelly soils)Type of irrigationOverhead(semipermanent)SurfaceOverhead(mobileequipment)SurfaceNumber irrigations per annum 1212I I11Amount of water, inches, applied perarpent per annum 307228209Yield of cane, tons per arpent 37,638.829.128.9Cost of irrigation per annum:Rs. per arpent 21698275145Rs. per ton cane 5.742.269.455.00Apart from the basic information which thisseries of experiments has provided, it has helpedconsiderably in focussing the attention of planterson the possibilities of overhead irrigation.The mobile equipment used for irrigating gravellysoils will be transferred to another estatein 1962 in order to compare the merits andlimitations of overhead and surface irrigationson dark magnesium clay soils. The experimentson free soils will continue at Palmyre howeverand I should like once more to take this opportunityof expressing my gratitude to the Managerof Medine S. E. for his kind assistance.When the Palmyre experiments were startedin 1957, there was only one overhead irrigationinstallation in Mauritius to irrigate about 150arpents. At the end of 196I a total area of3700 arpcnts was under spray irrigation asfollows: West 1150, North 700, East 1150,South 700. This area represents about 18% ofGROUNDThe electrical resrstivity survey started in1960 by the Compagnie Generate de Geophysiqueat Plaines WiIhems, Black River, Flacq andGrand Port was completed early in the yearand the broad conclusions which these investigationshave revealed are summarized below.the total irrigated area. Several estates haveplans for a further extension of overhead irrigationwith semi-permanent installations.Another important contribution to thedevelopment of spray irrigation is undoubtedlythe introduction of the "Boom-O-Rain" sprayer.This machine, which has rotating arms with aspan of 140', is provided with devices forcompensating to some extent the adverse effectof wind on spray distribution. Its long rangerenders it highly suitable for use in sugar caneplantations because it eliminates the necessityof penetrating into the cane fields for placementof the sprinklers and facilitates night workconsiderably. The machine requires roadsspaced at intervals of 220 ', This additionalcost, however, seems to be compensated by theincreased efficiency of the irrigation resultingfrom longer working hours and better waterdistribution.WATERThis work was extended later in the year tocover an approximate area of 120 sq. kms. atNouvelle Decouvertc, in the south east ofF1acq, Midlands and Chamarel.Meanwhile the programme of core sampling,bore hole drilling and pumping tests follow-

- 26-ing the electrical survey was continued byMessrs. George Stow as contractors withSir Alexander Gibb & Partners as consultants.The results obtained so far arc briefly reviewedbelow. The areas surveyed together with sitesof corings and borings arc indicated in fig. 11.Electrical survey of Plaines Wilhems, BlackRiver. Grand Port and Flacq. It has beenpossible to define clearly the main axes of therecent lava flows which have filled up the depressionsof older geological formations.CD COIl.~ HOtE,NEC"TIV{ OR UNCERTAIN IHSUlTLCD CORE HOtE,POSITIVE RESULTS.SIN"I~G Of WELL. POBIBLE.Q) CORE HOlE" "'ORE HOtf,PUMPING TEST VERY SATISFACTORY,@) CORE HOtE (, BORE HOLE-PUMPING TEH F"IR.CD CORE HOLE (, ~OREHOLE.PUMPING TEST NEC"T1I/E.® CORE aore , WELt BEING SUN«-. PROMISINCi.(j) BORt HOLE WITHOUT (ORE HOLE. N H.ATlI/E.& WELL ,PROMISING.® CORE HOLE c BORE MOLE NOT TESTED HT.D WELts.Fig. 11. Map of Mauritius showing areas surveyed by electrical resistivity (shaded). Sites of core holes,bore holes and wells are indicated.

-27-The first results obtained from the boreholes in the northern plain confirm the hypothesisthat the best water outputs are likely tobe obtained from the recent lava formations.In each sector sites have been selected forreconnaissance bore holes in order to assessthe possibilities of the different volcanic systems.In Plaines Wilhems and Black River theexistence of old weathered strata were found.They constitute a threshold which links up, wellbelow the surface, the bases of the old mountainousformations. These thresholds shouldbe very important with respect to the hydrologyof the region because they appear to be onlyslightly permeable and act as underground dams.However, from the geological standpoint, theexistence of these thresholds su bstantiates thetheory according to which the central region ofthe island is what remains of the collapse ofa large primary volcanic cone.Six systems of recent lava flows have beendifferentiated in the region and sixteen siteshave been selected for reconnaissance work.A weJl is being sunk at one of these sites andcore samples have been obtained from fourothers.In the sector of Flacq, three extensive groupsof lava flows have been brought to light, themost important one being that of Camp deMasque Pave - Caroline which has filled thedepression between Montagne Fayence andMontagne Blanche and acts as a channel formost cl' the water in the Trou d'Eau Doucearea. Northwards, the system of Riviere duPoste - Unite - Queen Victoria has filled smallloealized depressions whieh existed in the oldformations of the upper regions. Three siteshave been selected for reconnaissance workin these depressions. Finally towards thesouth east, the system Sebastopol - Petit Bel Airis probably the eastern limit of an importantflow. A total of nine boring sites have beenselected, A eore sample already obtained fromCamp de Masque Pave, and loeated in thehigher part of the central system, has confirmedthe great permeability of the strata.In the sector of Grand Port, the main recentlava flows have run across the sector from northwest to south east, filling on the way a series ofsmall depressions or basins in the ancient topography.Four of these depressions seem worthy offurther investigations by means of borings or wellsinking.Seven sites altogether have been selected inthis sector for reconnaissance work.From the results of the electrical survey ofthese sectors, it has been possible to draw up aprogramme of borings and pumping testswhich, together with hydrological data, willprovide a better knowledge of the possibilitiesof each sector. A total of thirty-two sites havebeen selected which will give indications as tothe best zones which should be chosen forfuture large scale exploitation of ground water.Drilling and Pumping Tests. At the end of1961 the following number of core drills andbore holes had been made.Core drillsBore holesDepth from 136 ' to 350' 54 ' to 250'North 16 14Flacq 8 3Grand Port 5 2PI. Wilherns/Black River 16 6Total 45 25In addition, four wells have been sunk bysugar estates at sites indicated by the CompagnieGenerale de Geophysique. Three of these wellsyield a large volume of water while work on thefourth is not yet completed.Twelve pumping tests have been made sofar, of which ten have given satisfaetory results.It was decided in December to stop the testsin view of the exceptional rainfall which occurredearly and late in this month. They will beresumed during the dry period, that is from Septemberto November. 1962.Observations on the water table werecontinued at 130 sites in order to obtain complementaryinformation on seasonal fluctuationsand movements of ground water. The investigationson ground water will probably beeoneluded at the end of 1962.

-- 28-~FIELDEXPERIMENTAnONThe number of field trials harvested duringthe year was 151, of these III were on estatesand 40 on stations. Experiments standing forthe 1962 harvest arc distributed according tosubjects studied, as follows:Variety trial (one date of harvest) 20Pre-rclease variety trials (three dates of harvest) 13Ratooning capacity ... 2Final variety fertilizer trials (three dates ofharvest) 18Growing period of cane 2Clean vis selective cutting 12Fertilization and amendments:(i) Form and mode of application ofnitrogen(ii) Form of phosphate(iii) Phosphate on ratoons .(iv) Calcium & phosphate .(v) Form of potassium(vi) Gypsum(vii) Basalt(viii) High & low fertilization (demonstration)(ix) Balanced & unbalanced fertilization(demonstration)(x) Bagasse amendment(xi) Organic matterDiseases:(i) Ratoon stunting(ii) Gumming .(iii) Leaf scald ..(iv) Chlorotic streak(v) Soil microfloraPests:IS (i) Varietal resistance to stalk borer ...I (ii) Chemical control of Clemora6 (iii) Control of army worm62 Effect of herbicides on cane growth2 Germination studies ...3 Root studies223II6I32I42I33ISUGARMANUFACTUREResearch. The main research projectsstudied during the year are briefly reviewedbelow, a full account appearing elsewhere 111this report.(a) Curing of low grade massecuites inhigh speed centrifugals. Prior to the 1961crop, one factory (Mon Loisir) installed abattery of five fully automatic 48"x 30" ASEAcentrifugals, two of which run at 1700 RP Mwhilst the three others have a maximum speedof 1450 RPM. The machines are fitted withthe Ward-Leonard system whilst the reheatingof the rnassecuite is obtained with the help ofa closed circuit installation in which the temperatureand throughput of the heating water canbe raised within limits.A series of experiments with these machineswere carried out during the crop with theobject of studying the effects of rate of acceleration,of top speed and of temperature ofwater used for reheating on the purging of lowgrade massecuites, The results obtained haveshown that:(i) provided power is available, it isadvantageous to bring the machines to topspeed in three instead of four minutes, as thehigher rate of acceleration does not affectthe porosity of the bed of sugar crystals andresults in a gain in centrifugal capacity ofabout 6 per cent,(ii) a 48" x 30" centrifugal running at1700 RPM has 25 to 30% more capacitythan a machine of the same dimensions,but running at 1450 RPM. For reasonsdescribed fully elsewhere, the 1700 RPM maybe expected to cause a reduction in thesugar lost in molasses,(iii) sucrose losses by re-solution may beappreciably curtailed if water at 60°Cinstead of 70 to nOc is used for reheatinglow grade massecuites prior to centrifugalling.(b) Cooling of A and B massecuites,Further experiments were carried out during thecrop on the cooling of A and B massecuites incrystallizers, a practice which is not followed inmost other sugar producing countries. The results

-29-have confirmed those obtained last year * and willbe presentedat the forthcoming I.S.S.C.T. Congress.(c) Determination of retention in Oliverfilters. In 1961 seventeen out of twenty-threefactories were equipped with rotary vacuumfilters. These filters offer numerous advantagesover filter presses, but their juices cannot befed directly to the evaporator and must be sentback to the mixed juice. Thus, if the amountof impurities going through with the filtered juicebecomes excessive, a heavy load is placed onthe clarifiers, and clarification trouble may result.The best way to judge the performance ofa vacuum filter is to calculate its retention.As the chemists of several factories havc foundit difficult to calculate retention figures correctly,a study has been made of the various methodsthat may be used.(d) Determination of comparative sucrose% cane values for agronomic purposes. In orderto determine the performance of new canevarieties grown on an experimental scale, undervarying environmental conditions prevailing on anestate, the yield of commercial sugar per arpentshould be compared to that of standard varieties.Different methods which may be used forthe determination of cane quality for agronomicpurposes with the equipment normally availablein sugar factories are briefly reviewed and theiradvantages and disadvantages discussed. Themethod recommended is one based on the Javaratio corrected for fibre. It is simple andyields comparative sucrose % cane values thatfall well within the limits of accuracy set foragronomic purposes.(e) Refractometer vis densimeter Brix forthe chemical control of sugar factories. As aresult of preliminary studies carried out at theend of the 1960 crop, it was decided to workout dual chemical control figures on threefactories throughout the crop, one set based ondensimeter and the other on refractometer Brixvalues. Unfortunately the precision refractometersordered were received late in the year so thatcomparisons could only be made for one weekat one factory, two weeks at another and fourweeks at a third.The results obtained in 1961 confirm pre-vious findings and it is suggested that refractometers should replace densirnetcrs in all thefactories at an early date. However, it isrecommended that all laboratories be equippedwith refractornetres for the 1962 crop so asto allow the carrying out of parallel chemicalcontrols in each factory throughout the cropin order that the laboratory personnel maybecome acquainted with the new equipment.In addition, the factory staff would becomefamiliar with the higher purity values resultingfrom the use of the refractometer, especiallywith low grade products. After this transitionperiod of one crop, densimeters could be entirelydiscarded and the chemical control based onrefractometric Brixes only.(f) Hein Lehmann continuous centrifuge.A limited number of tests were carried out latein the crop with a Hein Lehmann continuouscentrifuge installed at Mon Loisir factory forthe curing of A and B massecuites. Themachine was placed close to the battery ofconventional batch centrifuges so that it waspossible to compare the sugar produced by thecontinuous centrifuge and by the batch machineswhen fed with the same massecuite. Themassecuite and sugar throughputs of the HeinLehmann centrifugal were also measuredduring the tests.The continuous machine consistently yielded,both with A and B massecuites, sugars of muchlower polarisation and higher moisture contentthan those from the batch centrifugals. Furtherthe capacity of the Hein Lehrnann is muchsmaller than that of a conventional machine.It should be pointed out, however, those boththe cost and the power consumption of theformer are much lower than that of the latter.Continuous centrifugals of the type used forthe tests stand little chance of competing withhigh speed modern centrifugals for the curing of Aand B massecuites in raw sugar manufacture,but it is reported that they have been usedwith success for affination work in refineries,(g) Power consumption of cane mills. ManLoisir factory is equipped with a five - mill tandemin which each mill is independently driven byan electric motor. Advantage of this installation• See Ann. Rep. M.S.I. R.l., 1960.

- JOwas taken to measure, with the help of arecording wattmeter, the power consum ptionof each mill under operating conditions duringperiods of 24 hours or more,The power consumption of each mill whenrunning free was also measured, Finally, onthe last day of the crop, the tail bars wereremoved and the power consumptions of theprime movers and gearings of three mills wererecorded.It was unfortunately not possible duringthis crop to vary operating conditions suchas hydraulic load, mill speeds, settings, etc. andto study the influence of these factors onpower consumption, but it is intended to takefurther measurements during the 1962 cropwith a view to interpreting the results morefully.(h) Filterability of raw sugar. A numberof average raw sugar samples from most factoriesof the island were analysed for starch,silica, gums, wax and phosphates with a viewto determining the cause of the poor filterabilityof some of the raws produced. Thefilterability values were determined by the Nicholsonand Horsley method.It seems that, under Mauritius conditions,starch is the main cause of poor filterabilityof certain consignments of raws. The deteriorationobserved in this connection during thepast few years appears to coincide with theextension of new cane varieties containing morestarch.A comparison was also made between theElliot, and the Nicholson and Horsley methods forthe determination of filterability. The resultsobtained indicate that the latter method ismore reliable and should be adopted if abetter assessment of the refining qualities ofMauritius raws is to be achieved.(i) Study of the rnieroflora of raw sugars.In a report issued in 1959 *, it was shown thatheavy financial losses arc incurred annually onthe raws exported from Mauritius. Theselosses were attributed mainly to the action ofmicro-organisms on raws of poor keepingquality.in 1960 a note was received by the MauritiusSugar Syndicate from Messrs. Tate & Lyle Co. Ltd.conccrnmg the deterioration, by highly ferrncnt.uiveosmophilic ycasts, of a parcel of4,300 tons of Mauritius raws which had beenstored in a large silo and reclaimed severalmonths later. It was stated that two distincttypes of yeasts had been isolated from thesugar and tested. One was of the normalosmophilic tyre and contained no invertase. butthe second was highly fermentative and containedinvertase. This second species of yeastwas present in considerable number and hadnot been encountered before in raw sugar.It was therefore decided to take up thequestion during the 1961 crop in order toascertain whether osmophilic ycasts arc normallyfound in Mauritius raws and, if so, in whatnumbers. Earlier in the year it was arrangedthat, while on leave in Europe, Mr. Antoine,Pathologist, and Mr. de Frobcrville, Assistant SugarTechnologist, should obtain as much informationas possible on this question. The problemwas discussed with Dr. Scarr of Tatc & LyleResearch Laboratories while Mr. Antoine visitedthe Ccntraalburcau voor Schimmeleultures atDelft in Holland. The valuable assistancereceived from these organizations is gratefullyacknov ledged.A preliminary screening of sugars from the23 factories started in October, followed byfermentative tests and plate counts on osmophilicagar. Of the yeasts encountered in someof the sugar samples. Saccharomyces rouxii wasthe commonest, but six other species were alsoidentified. Ycast content of massecuites asdischarged from the vacuum pans. of the massecuitefed into centrifugals after cooling, ofsugar and molasses, was determined in severalfactories. It appears at this stage that contaminationby osmophilic yeasts takes place inthe crystallizers, Recommendations on suitableprecautions will be made as soon as the resultsof investigations now in progress become available.Advisory Work. Several studies were carriedout and a number of recommendations made.. Weight and polarization changes of raw sugars exported to the U.K. Technical Circular No. 12, M.S.1. R.1.mimeo, 20 p.

-31-on vanous aspects of sugar manufactureand items of machinery, including modificationto juice heating system, mud filtration. caneknives installation, boiling house work, frothfermentation in molasses, reheating of finalmassccuites, control of temperature in Juiceheaters, chemical control and boiling housework, control of sugar in boiler water andchemical control.Mr. F. Le Guen resumed duty in July afterspending one year in England where he specializedin Instrumentation Engineering at NorthamptonPolytechnic. Throughout the crophis advice or services were often sought inrelation to instrumentation work, in particularthat connected with the checking, calibrating andBY - PRODUCTSsetting of pH controllers. tile repairing ofcuitometers, the setting of laboratory pH meters,of vacuum and temperature recorders and ofthermo-rcgulators.Miscellaneous. As during the previous years,routine work included the compilation ofweekly chemical control figures, the analysisof 3354 canc samples from the experimentalplots of the Institute. the standardizationof a large number of hydrometers during theintercrop and the dilution and standardizationof hydrochloric acid for distribution to laboratories.The Chemical Control Manual of theSociete de Tcchnologie Agricole et Sucriere hasbeen partly revised.Protein extraction from cane juice. Furtherwork was carried out in 1961 on the extractionof protein from cane juice with the objectof reducing the fibre content of the coagulate,thereby increasing its protein content and obtainingsufficient material for conducting feedingtrials.As a result of modifications brought to theinstallation, it was possible to obtain a coagulatecontaining about 23% protein and 12.5% fibreon a dry matter basis. Over one ton of theproduct was separated during the crop, half ofwhich was used in feeding trials on milch cows.Two trials were carried out, and in eachof them the "coagulate" replaced entirelyluzerne meal which constituted 20% of thebasic ration. The results of these trials haveshown that milk production was not affectedby the substitution of cane juice protein.Further work is in progress on both the methodof extraction of the protein and its dietary value.It should be pointed out that this projectwhich was initiated in 1960 was primarily orientatedon the production of a high protein mealin a form suitable for animal or even humanconsumption. But the whole question ofutilizing cane JUice protein, which is at presentused as fertilizer in the form of factory scums,is of interest. For this reason, detailed analysesof scums from several factories were made andtheir potential value as livestock feed is discussedelsewhere in this report. Experimentsto compare the value of cane juice coagulateand factory scums as a source of animal foodarc also in progress.By-Products Committee Report. The By­Products Committee completed their survey duringthe year and finalized tile preparation of a reportissued as Technical Circular No. 18 of theM.S.I.R.I. It is hoped that the large amountof information which has thus been madeavailable will be of practical value in indicatingpossible future avenues of development. Thereport also sets forth local factors which havemilitated against the success of several attemptsto develop by-products of the sugar industryin Mauritius in the past.I should like to take this opportunity ofthanking members of the Committee, in particularthe Chairman, Mr. M, Paturau, for theirvaluable contribution.

--- 32-LIBRAR YSince its inauguration in September 1960,the Bonamc Hall which houses the library ofthe Institute, has been open to readers interestedin the sugar industry and many members of thestaff of sugar estates, sugar planters and manufacturershave come for information and documentation.The library receives 298 periodicals, 139 bydirect subscription and 159 by exchange ofpublications of the Institute with other institutions.These cover a wide field of knowledgeand include journals on general science, soilscience, chemistry, botany, entomology, genetics,plant breeding and pathology. There are now70 titles on sugar cane agriculture and teehnologyand 97 on agronomy.During the year, a serious efTort was madeto complete our sets of periodicals and muchprogress has been done in this respect throughthe courtesy of the British National BookCentre, the United States Book Exchange andnumerous libraries over the world whose helpwe gratefully acknowledge. The library stockamounts to 6012 volumes. There were 827 newaccessions during the year and 949 volumeswere bound.A complete card catalogue of the librarycollection is now available. A microfilm reader isavailable and bibliographies arc also beingcompiled to facilitate research work.THE MAURITIUS HERBARIUMDuring the year 130 specimens have beenlaid in. About 30 of these were not representedin the Herbarium and included some newrecords for Mauritius. They also includeda batch of 53 Reunion plants collected andpresented by Mr. J. Bosser. Some valuablematerial was received from the Conservator ofForests and his staff, comprising some fineexamples of the rare endemic montane speciesof Cylindrocline and Vernonia.Among visitors to the Herbarium fromoverseas, we were glad to weleomc ProfessorHarold St. John, University of Hawaii, Honolulu,who spent two months in Mauritius andReunion collecting and studying in the fieldthe genus Pandanus. Professor St. John is atpresent engaged on a world monograph of thisgenus. Mr. J. Bosser from the Institut deRecherche Scientifique de Madagascar workedon the Gramineae of the Mascarene Islands.Work continued on the weed flora ofMauritius and leaflet No. 5 Artemisia vulgariswas pu blished. Progress with this series hasbeen rather slow owing to the absence of theauthors on overseas leave and also to the needfor obtaining accurate determinations of theweeds to be included in the leaflets.While overseas the Curator, Dr. R. E. Vaughan,worked at the Kew and British Museum Herbaria.A number of undetermined specieswhich had been accumulating in the MauritiusHerbarium were named and about seventyphoto-copies of rare and little known Mascareneplants not represented in the collections herewere obtained.Serious consideration has been given to theneed for a modern Flora to bring up to datethe standard work on Mauritius plants, namelyBaker's Flora of Mauritius and the Seychellespublished in 1877. As a preliminary step it isproposed that a check-list of all flowering plantsindigenous, naturalized, and commonly cultivatedshould be prepared and published. It wouldalso be necessary to describe the new plantsdiscovered during recent years and to monographcertain families and genera of which ourknowledge has considerably increased since theappearance of Baker's Flora. When this hasbeen done, a well illustrated, definitive Floracould be undertaken. At the moment familiesreceiving special study are the EbenaceaeOrchidaceae and Cyperaeeae.The services of the Herbarium have beenincreasingly used during the past year by GovernmentDepartments, schools and the public,and it is hoped that these contacts will extendstill further when the work and resources ofthe Herbarium become better known.

-33-Some of the more important recentlypublished books and original papers concernedwith Mascarene vegetation are given below:BERNARDJ, LUCIAI'O (1961). La mort de Berenice.Musee de Geneve No. 18: 12 - 14.GHATAK, J. & MANToN, I. (1961). A note on acytogenetic relationship between Adiantumconfine Fee from Africa and Adiantumrhizopliorum Sw. from Mauritius. J. Linn.Soc. (Bot.) 58: 79-85,1.1.HODGKIN, E. P. & MICHEL, C. (1960). Zonationof Plants and Animals on rocky shores ofMauritius. Proc. R. Soc. Arts Sci. Mauritius,2: 121 - 146, tA.LEMolNE, MARIE (1961). Une Squarnariaceefrutescente Peyssonnelia frutescens nov. sp,Rev. algol. N.S. 5: 173, 1. 16 - 17.LEROY, JEAN F. (1961). Sur les trois Cafeiersenderniqucs de l'Archipel des Mascareignes.J. Agric, trop. Bot. appl. 8 : 21 - 29.RIVALS, R. (1960). Sur la vie et les problemesde la destruction d' Oxalis latifolia Kunth.J. Agric. trop. Bot. appl. 7 : 398 - 405.SAUER, JONATHAN (1961). Coastal Plant Geographyof Mauritius. Louisana State UniversityPress.Annual Report for 1960. 105, xxxviii p., illus,An abridged French version was also issued.(Reprint from La Revue Agricole et Sueri erede L'J/e Maurire, 40 : 65 - 93).Occasional PapersNo. 5 ROCHECOUSTE, E. Botanical andagricultural characters of sugar canevarieties of Mauritius. I) Ebene 1/37andM.147/44. 7 p., 2col. pI.; figs.No. 6 WILLlAMS, J. R. Studies on thenematode soil fauna of sugarcane fields in Mauritius. 5) Notesupon a parasite of root-knot nematodes.(Reprint from Nematologica5 (1960): 37 - 42).No. 7 WILLlAMS, J. R. comp. A bibliographyof sugar cane nematology.12 p.No. 8 WILLlAMS, J. R. and MAMET, J. R.The insects and other invertebratesof sugar cane in Mauritius andReunion. 23 p.No. 9 GEORGE, E. F. An experimentto compare the selection of sugarcane varieties from seedlingsJ. 11th Congress of the I.S.S.eT.* Muchtime was spent on the varied aspects of organizingthe 11th Congress of the J.S.S.C.T. whichPUBLIC ATIONSGENERALbunch planted in two differentways and from others singly planted.35 p.; figs.: tabs.LeafletNo. 5 ROCHECOUSTE, E. and VAUGHAN,R. E. Weeds of Mauritius.7. Artemisia vulgaris Linn.(Brede Chinois), 3 p.; figs.Technical CircularsNo. 17 ANToINE, R. La lutte contre lamaladie du rabougrissernent desrepousses, 10, ii p.; diagrs.No. 18 By-Products of the Sugar Industryof Mauritius. 280 p., figs.Private Circulation Report.No. 15 Report on the 7th InternationalCongress of Soil Science and Visitsto Soil Research Centres in Europeand U.S.A., by Sydney M. Feillafe.April, 1961. 78 p.Article in «La Revue Agricole et Sueriere del'Ile Maurice».ROUILLARD, G. La sucrerie de Labourdonnais; notes historiques, 40: 8 - I J.will be held from 24th September to 12th October,1962. The headquarters for the Conference willbe at the M.S.J.R.J. where the opening session• Since going to press, several changes have had to be made in the organization of the 11th Congress as a resultof the severe cyclone which struck Mauritius on the 28th February. The Congress will be held from the 24thSeptember to 5th October. P.O. W.

-34-will be held on Monday, 24th September.Thereafter, field and factory delegates willseparate for a comprehensive programme ofvisits both in Mauritius and Reunion. Technicalsessions will begin on the 4th Octoberand will continue until the I1th. The elosingplenary session is scheduled for Monday the12th October. Films on various aspects ofmechanical harvesting and the transport ofsugar cane have been obtained from severalsugar countries, and an exhibition featuringbasic recent agricultural and manufacturinginformation on participating countries will beheld during the Congress.2. Meetings. In addition to meetings ofthe Research Advisory Committee which wereheld on three occasions, the following lectureswere given in the Boname Hall :26th January, 1961 - «La lutte contre la maladiedu rabougrissement desrepousscs» by Mr. RobertAntoinc. The lecturewas repeated at BelleRive under the auspices ofthe M.S.P.A. on 12th May.28th April, 1961 - «Les applications deI'energie atomique al'agriculturc» by Mr. P.Pelegrin, Head of Sectionof Applied Agronomy,Nuclear Research Centreat Saclay.23rd May, 1961 - Review of M.S.I.R.I.Annual Report for 1960;an account, by the Director.of the work carriedout by the Institute in1960.30th May, 1961 -- Review of the work carriedout by the Sugar TechnologySection of M.S.I.R.I.in 1960, by J. D. de R. deSt. Antoine.12th July, 1961 - «The growth of a volcanoin the South Pacific andthe development of itsvegetation» by Mr. HaroldSt. John, Emeritus Professorof Botany in theUniversity of Hawaii. givenunder the auspices of theRoyal Society of Arts andand Sciences, Mauritius.3. College of Agriculture. Courses oflectures of the College of Agriculture continuedaccording to arrangements made last year,namely in Sugar Technology, Plant Pathology,Botany of the Sugar Cane, Statistics and FieldExperimentation and Sugar Cane cultivation.4. Staff Movements. The following officerswent on overseas leave during the year,Messrs. Antoinc, Bcchct, de Frobervillc, Mayer,Parish, Rochecouste and Rouillard. Arrangementswere made for these officers to visit agriculturaland other research centres engaged in workof particular interest to them. The assistancereceived from the authorities concerned is gratefullyacknowlcdgcd.Mr. Antoine spent two weeks in Madagascarin February and again in Novemberwhen he was accompained by the Director inconnection with the control of Fiji disease onthe east coast of Madagascar.Mr. S. Feillafe spent a week in Reunion inconnection with soil studies.The Director was absent from the end ofAugust to early October visiting the ChagosIslands and the Seychelles.The assistance given by sugar estatemanagers and their personnel has been asusual of the greatest value and it is a verypleasant duty to record my own appreciationand that of the staff for the help received in theexecution of field and factory experiments.Finally, I should like to thank all members ofthe Stafffor theirloyal co-operation during the year.!~Director9th February, 1962.

Fig 12. Top . Some of the se lf-sow n seed lings from a na tural cross disco ver ed at Union Par k a t the end ofthe year. The (WO lar ge see dlings in the centre a re a bo ut J8 inches highBottom. The marked d iffer ence I seedling g rowth in ca ne lea f pots (left) and poly then e pot s, Tagson indivrd ua l shoots a rc to record survival.

CANEBREEDINGE. F. GEORGE & W. de GROOT1. ARROWING(i) Conditions in 1961.THE estimates of the percentage floweringin various commercial cane varieties havenow been made since 1956 with thevaluable help of estate managers. This year'sresults from the counts of flowers in estate fieldsare given in Table I, while recent annual fluctuationsin the flowering of three major varieties!lre given in Table 2.The flowering percentages of 1961 werevery low, even compared with 1960, a yearwhich from the breeders' point of view wasthought to be the worst possible. This resultis almost certainly due to the severe droughtearly in 1961, which caused a retardation ingrowth (cf. fig. I 011 page 10), so that the caneswere too small at the critical time for flowerinitiation.The variation in percentage of arrowingwith years is certainly due to weather conditionsbefore and during the time of initiation. However,a method to predict the amount of flowersfrom weather characteristics has not yet beenfound as the results from normal years arestill too scarce.The variation in percentage of arrowingwith the date of harvest of the canes the yearbefore could not be determined, as the differenceswere too small at this low floweringintensity.A few arrows emerged in the field atReduit in early January. As far as is knownthis was the first time that out-of-seasonflowering has occurred in Mauritius. Thevarieties which flowered were chiefly S. spontaneumselfs, but one normal flower was foundof C.B.38-22. This· was crossed with a self ofS. spontaneum and gave rise to 50 seedlings.Due to lower mean temperatures the developmentof an inflorescence could be expectedto be slower in the spring than is normal in theautumn. This means that induction of theflowering stimulus probably took place inSeptember 1960 at approximately the samedaylength as would be inductive in the autumnbut in lengthening days. It is sometimes statedthat progressively shortening daylengths arenecessary for floral induction in sugar cane.Table 1. Average percentage arrowing in 1961*Variety North South East West Centre AverageEbene 1/37 2,15 1,66 2,06 1,62 1,87M.147/44 0,78 1,01 1.16 1,29 0,13 0,94M.134/32 1,44 0,52 1,00 0,79 (0,00) 1,05B.37172 0,36 0,22 0,36 (0,00) 0,31B.3337 0,15 0,15 (0,17) 0,15M.31/45 0,38 0,26 0,32M.202/46 (1,95) (1,95)B.34104 (1,04) (0,00) (0,71)M.93/48 (1,55) (1,55)Ebime 50/47 (0,00) (0,00)M.112/34 (0,00) (0,00)B.37161 (1,95) (0,33) (0,00) 0,91• Results derived from less than 5000 canes are placed in brackets.

-36 ---Table 2.Year195619571958195919601961Average arrowing percentage of different varieties over the whole island.M.134j32 M.147j44 Ebene Ij3722,5 13,I9,3 10,15,4 4,6 6,16,9 3,0 6,42, I 1,7 1,51,0 0,9 1,9(H)Control of flowering.Several photoperiodic experiments whichwere carried out on the variety C.P. 36-13 in1959 were successfuJIy repeated during the year.Cyclones in 1960 severely damaged treatedcanes so that results were not reliable.These experiments have indicated tlzit theprocesses of flower induction and subsequentdevelopment are not entirely independent.Extra light at night given to canes at an appropriatetime of the year had an effect on threerelated phenomena: the time at which an inflorescenceis first formed, the time of arrowemergence and the intensity of flowering. Theseeffects of extra light treatment have a very closeparallel in the differences in flowering habitsbetween varieties of sugar cane in the field.For example, extra light treatment in C.P.36-13 caused a delay in the formation ofinflorescences, a further delay in their eventualemergence and a reduction in flowering intensity.Varieties which do not flower heavilyin Mauritius also exhibit a delay in inflorescenceformation and emergence relative to freelyflowering varieties. These changes, followinglight treatment in the variety C.P. 36-13, andsubsequent on genetic control in shy arrowingvarieties, very probably have a common causewhich may be due, in the simplest explanation.to a reduced concentration of flower-promotingsubstances.Several other experiments to induce orretard flowering were executed during theseason, but as the flowering intensity was low,no valid comparisons could be made.2. CROSSING(i)Programme.The scarcity of flowers, as indicated by thelow percentages of arrowing in commercialvarieties, made the execution of a normalcrossing programme difficult. However a largenumber of crosses was made, although thenumber of combinations between the variousparents was slightly less than the year before,which in itself was a bad year.The marcotting techniques described in theAnnual Report for 1960, were again used forthe isolation of canes for crosses inside thegreenhouse. Some further experiments on thetechniques which have been evolved wereconducted and the results obtained were inagreement with those from last year.The method to induce rooting before externalsigns of flowering are visible, was unsuccessful,in so far that no flowers were obtainedin the 500 stalks brought into the greenhouse.This method only seems applicable duringyears in which flowering is normal, when afair amount of arrows in the treated stalkscan be expected. Canes marcotted in the fieldwhich had formed sufficient roots before theflower protruded, were afterwards cut andtransplanted into concrete or iron pipes. It isfound that subsequent growth and developmentis better if transplantation is employed. Manycanes this year had to be used for crossingas soon as they were seen to flower in thefield and with no prior treatment. In this case,marcottes were applied after severance of thestalks and the cut ends were placed in an SOzsolution.

-37-This last mentioned technique was shown tobe justified by the results of an experimentconducted during the season. From fourvarieties 4 flowering canes were marcotted and4 not. All the stalks were placed in 4 gallondrums (4 canes per drum) with an SOz solution,which was changed every other day. All theflowers were pollinated by the same malevariety in one area cross. Marcotted canes didproduce significantly more viable seeds thannon-marcotted ones. (Table 3).It has been reported from Barbados thatrain water is better than tap water for thepreservative solution. This too was tested in theexperiment but no difference in seed setting wasfound attributable to water from either source.The total number of crosses made thisyear was 701, from which 252 were made inthe open. A summary of the crossing workis given in Table 4, while the list of crosses canbe found in the Appendix (Table XXIII). Thenumber of parents used in the programmewas enlarged with some varieties of theM./57 series. Again during selection, newparent varieties were planted in the breedingplots.About 50 seedlings of unknown parentage,resulting from natural crosses, were discoveredat Union Park S. E. S. in December havingestablished themselves at the edge of a field(fig. 12). They were transplanted for subsequentassessment.Table 3.The number of seedlings produced experimentally from female stalks marcotted andnot marcotted and placed in tap water or rain water.Cross Rain water Tap waterNot marcotted Marcotted Not marcotted MarcottedP.R.lOOO x 47R2777 3630 2300 2310 306080 2100 330 3590Ebene 1/37 x 47R2777 29 2360 460 14201030 920C.B.38-22 x 47R2777 1140 270 340330 370 140 160M.241/40 x 47R2777 620 3750 290 281051 1380 500TOTAL 5880 11910 5180 12800Total rain: 17790 Total tap: 17980Total not marcotted : 11060 Total marcotted: 24710Table 4. Summary of crossing work in 1961.StationReduitPamplemoussesF.U.E.L.BritanniaTOTALNo. crosses madeinside449449outside129123No. seedlings obtainedinside outside total47319 35160 8247923539 23539252 47319 58699 106018No. seedlings plantedsingly bunched*5431 1374156 6257268516909587 10769• In a bunch 7 - 8 seedlings are potted together; at the time of planting approximately S seedlings/bunchare still alive.

-38-(ii)Transplantation of seedlings.As in 1960 most of the seedlings werebunch planted. The value of polythene potswas again tested. Seedlings from 7 differentcrosses were bunch planted in both straw andpolythene pots so that a comparison could bemade on the effect of both types of container onsubsequent growth. This experiment wasextended so that the survival of individualseedlings in bunches eould also be observed.Individual seedlings were ringed from a veryearly stage and a subsequent record kept ofsurvival, length and tillering until the timeseedlings were established in the field. Theaverage growth rate of the seedlings in polythenepots was, in all the 7 progenies, superiorto that in staw pots. This can be seen fromTable 5.Table 5.The average shoot length of seedlings of different crosses all measured on the same dateCross No. Average length of seedlings61-684-438-710-602-442-591-461Straw potsems46.051.833.243.035.751.769.5Polythene potscms62.878.334.453.862.265.073.5Shoot length was significantly better mpolythene pots (P = 0.00I).Fig. 12 shows the marked difference betweenthe seedlings of cross 61-438 in the two typesof pots.Table 6.Cross No.The mean number of seedlings surviving and the mean number of shoots per pot.Surviving seedlings/potMean no. shoots/potStraw Polythene Straw Polythene61-684 5.3 7.7 8.0 16.0-438 4.2 4.0 7.0 7.5-710 2.3 2.5 4.0 5.7-602 5.3 6.2 8.5 11.7-442 3.2 4.8 4.7 7.5-591 4.7 4.8 6.0 10.5-461 5.3 4.2 9.8 7.0Weighted means 4.3 4.9 6.7 9.4From Table 6 it is also revealed thatsurvival is not significantly different in polythenepots but that the number of shoots perpot tends to be higher.It therefore appears that polythene potswill in general give better seedling growth andconsequently they will probably be used exclusivelyin the future.

-39-3. STUDIES ON SEEDLING POPULATIONS(i) Selection in bunch planted seedlings.The result of an experiment started in 1956and mentioned in the Annual Reports for1958-1960 have finally been calculated andsent to press. This emphasises the great dealof time required for evaluating the results ofthis type of biornetrical experiment. Theactual measurements taken in the field, althoughfairly time consuming, are small in proportionto the work involved in their interpretation.The experiment referred to, compared theselection of varieties from seedlings bunchplanted in two different ways and from otherssingly planted. It was found that selection infirst ratoon from both methods of bunchplanting was effective and resulted in a similarselection rate as was obtained from singlyplanted seedlings.In the seedlings which were studied, selectionfor weight of cane and all contributingfactors was most effective from those whichhad been singly planted originally, the potsafterwards being placed together (7 in onebunch) in the field. The same selection ratewas obtained as from single planting. Seedlingsnormally bunch planted gave an inferiorselection rate for these characters. Very probably,if sugar content had not been negativelycorrelated with yield components in the seedlingsstudied, then bunch potting, as the newmethod was called, would have been the bettertechnique. As it was, many of the high yieldingselections from bunch potting were of low brixand were discarded bringing the eventualselection rate back to a figure comparable withbunch planting.o-;;;":230]z :2208r 2 10" ~ 200J 190~ 180::l; 170«"oLENGTH';;'DIAMETE~NO OF CANES~ 22'" ,~ a a ,.» ~ 20,,/" ~ 32• '8o/ ~ 3 ro z~ 30z " aA A+ c- C c+ a- .+ A- A A. c- C c+ 8 -•GRADE OF SELECTED STALKS8+ A_ A A+Fig. 13. The selection which could be achieved in nine measured characters by choice of stalks of differentgrades from bunch planting and bunch potting.Open circles, plain line; within the varieties from bunch planting.Crosses, broken line; within the varieties from bunch potting.

-40--The efficiency of selection practised by thechoice of stalks of different calibres fromeither bunch planting or bunch potting isillustrated in fig. 13. The nine graphs in thisfigure correspond to the characters measured inthe bunch selection plot. In each, the meanvalue of groups of varieties is plotted againstthe various grades of selected stalks from whichthe members of each group were derived. Thusthe slope of the regressions of y on x (bunchselection plot value on single stalk grade),calculated separately for the bunch plantingand bunch potting samples, gives a figure forthe respective efficiency with which selectioncould be practised in each character by thechoice of stalks of different qualities in the previousgeneration.Measurements were made III the fieldduring the year on another bunch plantingexperiment designed to measure the superioritywhich would be expected in random selectionsfrom bunch planting if seedlings of poorquality arc discriminately eliminated. Resultshave yet to be calculated.(H)Progenies in contrasting environments.Seedlings of six crosses planted during 1959at the 4 Experiment Stations in randomiseddesigns with two standard varieties were measuredduring the year. Special thanks are due tothose students of the College of Agriculturewho helped with this work which was a morerefined repeti tion of an earlier experiment(GroRGE, [960) and endeavoured to assessadaptation exhibited by seedling progenies.At the time of writing most of the results ofthis work have been calculated. Among thefinding, which will be published elsewhere,estimates arc given of the expected efficiency ofselection in each environment for the characters,average length, average diameter, numberof canes, flowering intensity, brix and grade(the selector's appraisal of the worth of eachseedling). These estimates are being checked intwo other experiments which were planted withthe seedlings showing the best expression ofthe above characters in each cross and in eachenvironment. The response to selection will bemeasured in comparison with a random choiceof varieties from the six progenies at each place.These studies have suggested that a veryuseful method of parent-progeny evaluationwould be a factorial set of crosses where severalfemales arc crossed with the same males.Accordingly one such experimental comparisonhas been planted in the field at Reduit this yearwith progenies from the varieties Ebenc 1/37,C.B.38-22, N.Co. 376, P.R. 1000, M. 212/56crossed with M.147/44 and 47R2777.4. SELECTIONDuring the year canes grew well and mostof the trials could be harvested, resulting inmany selections. Recent changes in the programme,as described in the Annual Reportfor 1960, were incorporated in the selectionschemefor the first time. All seedlings, of theM./59 series selected from single plantings at the4 Experiment Stations (a total of 1100), wereeach propagated in two plots; one in the warmhumid area (Reduit and Pamplemousses S.E.S.)and one in the super humid region (Belle Riveand Union Park S.£.S.)Normal bunch planted seedlings of the 1960series were selected in virgins at PamplemoussesS.E.S. and at F. U.E.L. sub-station and theselected stalks were planted in bunch selectionplots at the same places. As selection inbunches is merely visual, well developed plantationscan be selected in virgins. Howevergrowth at Reduit S.£.S. and at Britanniasub-station was not satisfactory and selectionthere had to be postponed until the canes haveratooned in 1962.During this season it was concluded fromresults obtained from propagation plots, thatselection in virgins in these trials is not reliable.The present policy of selecting original plantationsin ratoons, does not seem to be a sufficientsafeguard against canes with weak ratooningcapacity entering propagation plots. A definiteassessment of at least the ability to grow wellin first ratoons is necessary and apart from a

~- 41few varieties which look very promising, novariety will be planted in first selection trialsuntil the results of ratoons in propagationplots are available.A total of 125 selections of propagationplots were planted in 6 first selection trials onthe 4 stations. 16 first selection trials wereharvested, from which 32 selections were made.Some of the more promising selections, nowin multiplication plots for planting in trials onestates in 1962 are the following:M.17/55 (M.311/41 x M.423/41). A varietyselected from a first selection trial atReduit S.E.S. High yielding canealthough sugar content is inferior.This variety grows erect, trashes easilyand until now no flowers have beenobserved.M.69/55 (B.34104 x M.63/39). Cane ofmedium thickness and good growthhabit; outyielded the standard (M. 147/44)at Reduit.M.217/55 (B.34104 x M.213/40). Selectedat Pamplemousses S.E.S. The varietygave a high yield in 1st ratoons andsugar content was good.M.255/55 (B.34104 x M.63/39). Selectedin l st ratoons at Belle Rivc S.E.S.where it gave a very high yield (25 %more than Ebene 1/37); sugar contentwas only slightly below that of thestandard. The variety trashes easilyand growth habit is semi-erect. Gcrminationis fair. Some flowers have beenobserved in propagation plots in 1959.M.303/56 (Ebene 1/37 x M.213/40). Selectedat Union Park S.E.S. in firstratoons. A semi-erect cane trasheseasily and is of medium thickness.Sugar content was quite good andyield was about the same as fromEbene 1/37.A summary of selection is given in Table 7.Table 7. Summary of selection work in 1961No. of stalks No of No. of selections No. of selectionsStation planted in seedlings made in made inB.S.P. selected Prop. plots F. Se!. Trials.Reduit 133 172 37 I3Pamplernousses 2014 287 20 10Belle Rive 464 44 5Union Park 175 24 4F.U.E.L. 1407BritanniaTotal 3554 1098 125 325. VARIETY AND PRE-RELEASE TRIALS.During the year 1961. 10 variety trials and3 pre-release trials were planted, while a totalof 36 trials (26 and 10 respectively) were harvested.Six trials have been abandoned afterthe result of the 1961 crop were known. Thedistribution of the various trials over the islandis given in Table 8. A total of 114 varieties(97 M. varieties, 7 Ebene varieties and IOimported varieties) are being tested in thesetrials.

-42--Table 8.Distribution of trialsYear of plantingRegionSubhumid Humid Superhurnid IrrigatedTotal1957 2 2 41958 5 I 2 91959 3 5 2 111960 2 2 2 61961 2 5 4 2 13Total 4 17 14 8 43Some of the prorrusmg varieties in thesetrials gave the following results in 1961:P.B.12/59 Irrigated region1st RatoonM.305/49 - Results of trial P. B. 6/59 in1st ratoons at Richc en Eau in the superhumidregion indicate that this variety might producewell during a normal year in the humid region.Sugar content was quite good, but yield was onthe low side.Ebene 1/37 B.3337 M.305/49T.e.A. 35.9 47.0 40.9I.R.S.e. 9.6 9.7 10.4T.S.A. 3.44 4.55 4.28Maturity was good in the middle of theseason. In other regions, due to dry weatherearly in 1961, yields were not so satisfactory.M.442J51- Results from 2 trials in ratoonsseem to indicate that this variety can producea fair amount of cane.T.C.A.I.R.S.e.T.S.A.M.4U/51 is now planted in pre-releasc trialsin the 4 main regions of the island from whichmore data will be available after harvest in 1963.M.658/51. This variety grows well in thehumid region. In a trial at The Mount S.E.,P.B. 3/57, the following results were obtainedin 1961 (3rd ratoons) :T.S.A.I.R.S.C.T.S.A.M.147/4429.511.03.25M.134/3235.711.34.02M.442/5I31.811.03.50M.658/5148.911.05.38T.e.A.I.R.S.e.T.S.A.P.B. 4/57 Humid regionRatoons (Average l st & 3rd)Ebene 1/3739.210.34.02M.442/5I51.78.54.40The variety must be multiplied and testedin other regions before its value can be assessed.M.117/55 which gave very promising yieldsin virgins, was disappointing in ratoons.From the imported varieties, R.397 gavegood results in pre-release trials under warmconditions where a fair amount of water wasavailable. In the subhumid area, results werethe same as for the standards M.147/44 andB.37172.

-43-6. RELEASE or THE VARIETIES EBENE 50/47 AND M.253/48The Cane Release Committee decided inDecember that the varieties Ebenc 50/47 andM.253/48 should be recommended for releasefor commercial cultivation.Ebene 50/47. This variety was bred atHighlands S.E.. and as far as is known itsancestry is as follows:r.o.r 2878 x Uba MarotIy-M.134/32RH.lOjl2x unnumbered seedlingIy-x unnumbered seedlingIy-Unnumbered seedling x unnumbered seedlingI-v-(P.a.J. 2878 x Co. 301)Ebene 50/47Material of this variety for planting intrials became available in 1958 and was multipliedand tested during the following years.Results obtained so far indicate that it is ahigh yielding cane with excellent sucrose contentthroughout the harvesting season. Floweringis medium to free; the cane is of mediumthickness, has an erect habit of growth andtrashes easily. Information about ratooningcapacity is not yet available.The cane is susceptible to ratoon stuntingdisease, chlorotic streak, red stripe, pokkahboengand eye spot; resistant to gumming andleaf scald, while resistance to stalk borer (Proceras)is intermediate.A summary of results of the variety Intrials on estates is given in Table 9.Table 9.The percentage superiority of Ebene 50/47 over the standard in variety trials.The actual results of the standard are given in bracketsTrialRegionStandardNo. of RatoonsT.C.A.I.R.S.C.T.S.A.Fibre1*341 % (2.23)146 % (5.70)485 /~ (0.13)129/~ (9.87)P.B.15/58HumidEbene 1/372106 % (44.69)121 /~ (9.17)128% (4.10)110% (9.70)P.B.9/59SuperhumidEbene 1/37I120/~ (14.12)109% (8.60)131% (1.22)100% (9.79)P.B.12/59IrrigatedM.147/44I86% (29.50)117 % (11.00)102/~ (3.25)89% (13.87)• Results cyclone year 1960.Table 10.Percentage superiority of M. 253/48 over the standard variety in pre-release trialsThe actual results of the standard are given in brackets.TrialRegionStandardRatoonsT.C.A.I.R.S.C.T.S.A.FibreP.B.5158HumidEbene 1/372115 /'~ (20.82)101 % (10.3)115% (2.16)85% (12.9)P.B.7/58Sub-humidM.147/442110% (28.0)91 % (10.8)100 % (3.02)74/1,; (14.6)P.B.3/59HumidEbene 1/37I132% (28.9)101% (9.9)132 % (2.87)88 /~ (10.7)P.B.6/59Super-humidEbene 1/37I124/~ (35.9)107% (9.6)133% (3.44)99% (8.8)

-44-M.253/48 - This variety, derived from thecross B.34104 X M.213/40, is planted now on anarea of about 800 arpents after the decision ofthe Committee in 1959 to advise cultivationunder certain conditions. It has now been todecided to recommend M.253/48 for releasebecause of its continued success in irrigatedareas.Selected in 1950 and subsequently tested atthe Pamplemousses S.E.S., the growth of thisvariety in trials was good compared to M .134/32,while sugar content, estimated by hand refractometerbrix, seemed to be reasonable. In1954 the variety was planted in a variety trial.Results of subsequent pre-release trials are givenin Table 10.Canes of M.253/48 are thick and the trashis easy to remove. The variety is vigorous andcapable of giving high yields especially inirrigated regions.Sugar content is low at the beginning ofthe crop, but improves towards the end of theseason. Fibre content is very low and purityis good. M.253/48 is resistant to gumming,leaf scald, red rot and po kkah boeng, verysusceptible to chlorotic streak and susceptibleto ratoon stunting disease and stalk borers(Proceros).The cultivation of M.253/48 in areas otherthan those irrigated or receiving high rainfallcoupled with plentiful sunshine and high temperatures,cannot be recommended. Thisvariety is best adapted to only a small rangeof the environments met with in Mauritius.The maturity behaviour of both Ebene50/47 and M. 253/48, as obtained from virgincanes in all sectors of the island, is showndiagramatically in Fig. 14.~zu '0'"Fig. 14.EBHH )0/0OATE- .. -------- •• 110~--_., .0JUNE seer NO'o' JUNEOf i"AF,'II(H'0HPTDATE OF HARVESTMaturity behaviour of released varieties.Average of 10 final variety trials harvested in virgins.Open circles; compared to Ebenc 1/37.Close circles; compared to M. 147/44.REFERENCEGEORGE, E. F. 1960. Effect of the environment on components of yield in seedlings from five Saccharum crosses.Proc. into Soc. Sug. Cane Tech. 10: 755 - 765.

NUTRITION AND SOILS1. MINERALOGICAL COMPOSITION OF SOME LOCAL SOILS.D. H. PARISH & S. M. FEILLAFETH E work of CRATG 2 , and CRATG & HALAIs 3on the chemical composition of localsoils led to the conclusion that withincreasing rainfall the amount of silicate clayminerals in the soils diminished and that thelarge increase in 'combined water' with increasingrainfall indicated increasing amounts of thehydrated oxides of iron and aluminium.No specific identification and assessmentof the minerals of local soils was however made.As finally, an accurate picture of these mineralsis essential to the full understanding of thepedogenic processes, the opportunity was takenof having a few exploratory X-ray analyses ofsome local soils carried out at RothamstedExperiment Station. The results of these analysesare given in Table 11. and the opportunityis taken here to express our thanks toDr. A. Muir, Head of the Soil Survey of Englandand Wales, who arranged for the samples to beanalysed and to Mr. G. Brown for actuallycarrying out the analytical work.Table 11.X - Ray Analysis of the Clay Fraction of Some Local Soils.Great Soil Group Site Kaolin Montmo- Goethite Haematite GibbsiterilloniteLatosolic Reddish Prairie Mapou dominant present presentLow Humic Gley Petrin *Dark Magnesium Clay PlaineLaUlun v. little dominantHumic Ferruginous Latosol Chamarel dominant present * present *Humic Ferruginous Latosol Belle Rive v, little ** •••Low Humic Latosol Reduit dominant **Latosolic Reddish Prairie PetiteC. Noyale *Low Humic Latosol Solitude present*Low Humic Latosol Anse *JoncheeHumic Latosol Ferney moderate ** present **Latosolic Brown Forest R. Belle v. little ** **Latosolic Brown Forest Melrose moderate * **For the AI silicatesFor the iron oxide s, and gibbsite:v. little 5-10% present < 5%little 11-25% present."} S - SO~~moderate 26-50% ••dominant >50% present *** > 50%

-46 --The results for the aluminium silicateminerals have been more precisely defined thanis the case with the iron and aluminium oxides,as these latter materials present some difficultiesin quantitative X-ray work.Apart from the dark magnesium clay greatsoil group, which 8,S is well known, is a predominantlymontmorillonitic clay, 2: 1 latticeclays apparently do not occur III the freedraining soils of Mauritius.The typical titration curve? of soils fromthe Mapou area gives an inflexion around pH7and in view of the fact that the pH of thesesoils is around neutrality and the solurn containsnumerous particles of the parent dolcriticbasalt, it was felt that, even though the soilsare free draining, possibly some montrnorilloniticclay had been formed. This opinion wassupported by the work of SHERMAN and UEHARA 6who found that montrnorillonite was formed incavities in the parent rock and particul.irlyimmediately underneath the boulders wherethe soil is protected to some extent fromexcessi ve leaching.The X-ray analyses of the clay fraction ofthe !VI apou soil however have not demonstratedthe presence of montmorillonite.In Table 12 the soils have been dividedinto two groups. immature and mature and thenarranged in order of inc.casiug rainfall. Chemicaldata obtained during the soil survey and theestimated average mineralogical compositiontaken from the data in Table 11 arc given.The table shows clearly the rapid declineIn silica content with increasing rainfall and thecomplementary decrease in the ratio of silicato aluminium oxide. The most important pointfrom the mineralogical data is the increase ofthe aluminium oxide - gibbritc - at the expenseof kaolin; tile goctuite content also tends toincrease with iucrc.ising rainfall but not somarkedly as gibbsitc.These Xvr.ty analyses are only of an exploratorynature and the whole subject of themineralogical composition of local soils willhave to be studied in detail later. The dataobtained so far, however, are interesting in thatthey confirm tile broad interpretations whichhave been made of the chemical data.Table 12.The effect of increasing rainfall and age 011 the chemical composition of the wholesoil and the estimated mineralogical composition of the clayMATURESOILS.Average yearly Soil ClaySire Rainfall Si0 2 % Si0 2/A1203 Kaolin Goethite GibbsiteSolitude 50" 32 2.0 > 50 50 35 50IMMATURESOILS.Average Yearly Soil ClaySire Rainfall Si0 2 % Si0 2/A 1 2 ° 3 Kaolin Goethite GibbsitePetite Case40" ')Noyale 1- 32 2.0 > 50 < 25

-47-Agricultural significance of the data presented.From the point of view of agriculturists,perhaps the most significant point of theresults so far available is the low level ofsilicate material occurring in the soils of thesuperhumid zone, and particularly so for themature soils of the area.Sugar cane is known to take up largeamounts of silica and the amount taken up bya healthy crop is directly related to the silicacontent of the soil, and therefore to rainfall.The application of crushed basalt to thehighly leached mature soils of the superhumidzone, soils which have a very low content ofkaolin, has given big increases in cane yields",Comparisons of the mineral composition of thecane crops grown on basalt-treated plots andcontrol plots have so far shown only onemarked difference, namely that the level ofsilica in the crops from the basalt-treated plotsis much higher than in the controls. This increaseduptake of silica is very highly correlated withthe increase in yields obtained.As a high level of silica in the leaves isknown to exert a counteracting effect onmanganese toxicity", it could well be that part,at any rate, of the effect of adding crushedbasalt to these low aluminium silicate soils isdue to the increased uptake of silica by thecane crop and resultant elimination of somemetal toxicity.Results from Hawaii! have shown thatsome soils give improved cane growth whensodium meta-silicate is applied and this may betaken as supplementary evidence to the viewthat although silica is not considered as anessential plant nutrient, it nevertheless seems toplay a physiological role under certain conditions.In view of these findings, experiments havebeen laid down in which the relationship ofsilicon to other inorganic constituents of plantsis being studied.REFERENCESI. CLEMENTS, H. F. t960. Proc. iut, Soc. SUIf. CaneTech. 10 : 523 - 282. CRAIG, N, 1934. Some properties of the sugarcanesoils of Mauritius. BI/I/. No. 4. Sug: CaneRes. SIa. Mauritius3. CRAIG. N. and HALAIS. P. The influence of maturityand rainfall on the properties oflateritic soils in Mauritius. Emp, J. Exp. Agric.2: 349 - 58.4. PARISH, D. H. and FEILLAFE, S. M., 1957. TitrationSug.curves of some local soils. Afln. Rep.Ind. Res. Inst. Mauritius. 1956: 43 - 46.5. PARISH, D. H. and FEILLAFE, S. M., 1959. Areview of organic and inorganic amendmentsused in cane cultivation. (C. Basalt dust.) Ann.Rep. Sug. Ind. Res. Inst; Mauritius. ~: 81.6. SHERMAN, G. n, and UEHARA, G., 1956. Theweathering of olivine basalt in Hawaii and itspedogenic significance. Proc. Soil Sci. Soc. Amer20: 337 - 407. WILLlAMS, E. and VLAMIS, J.• 1957 The effectof silicon on yield and manganese 54 uptakeand distribution in the leaves of barley plantsgrown in culture solutions. Plant Physiol.52: 404-092. IMPROVEMENTS IN LEAF SAMPLING TECHNIQUE FOR FOLIAR DIAGNOSISPIERREHALAISTwo major improvements have been introducedfor the regular sampling of ratoon caneleaves during the critical hot and wet periodbetween mid-December and mid-April priorto cane flowering. They are:I. Adequate MoistureIf the weekly elongation of adequatelyfertilized primary stalks is 10 cm or more, thenit is considered that the cane has not suffered

-48-from moisture stress and leaves can therefore besampled.In order to save the considerable workinvolved in making elongation measurements, amoisture index has been worked out from dataobtained during the 1961 summer drought ateight representative sites.The correlation coefficient between elongationand rainfall is +0.85 and its significanceexceeds the I % level. The regression equationcalculated is as follows:E (elongation in ems) = 0.081 R + 1.64where R is the total rainfall of the precedingthree weekly periods, with the proviso thatshould the rain exceed 50 mm in any week,then the surplus is not considered and only50mm are credited. The maximum value ofR is therefore 150 mm and the requirementfor 10cm growth is 100 mm.Taking 10cm as the required elongation,then from the equation it is seen that a validleaf sample can be taken when a well distributedrainfall of 100mm or more, i.e. fourinches or more, has occurred in the three weekspreceding sampling. If the value of E doesnot reach 10 cm, then sampling should bepostponed until the moisture index is sufficientlyhigh for at least two consecutive weeks.2. Age of ratoonsThe basis of foliar diagnosis is the levelof nutrients in leaves from ratoon cane of fivemonths growth. The work of INNES 1 inJamaica has shown that the nutrient contentsof leaves change in a systematic fashion withage and using his data it is possible to sampleleaves on ratoon cane from 3 months up to 7months old and to correct the analyticaldata obtained to a standardized age of fivemonths (Table 13).Table 13.Age correction for nutrients levels to obtain standardized dataAge in months of ratoon cropNormal age3 mths. 4 mths. 5 mths. 6 mths. 7 mths.N%D.M. -0.32 -0.09 1.95 to.08 +O.ISP20S -0.08 -0.02 0.48 +0.01 +0.03K 2 0 -0.03 -0.00 !.SO +0.06 +0.14These correction factors, therefore, now allow a wider latitude in sampling age withoutloss of accuracy.REFERENCE1. INNES. R.F. (1959) The manuring of sugar cane. SPAN 2 (3) 98·100.3. COMPARATIVE ROOT STUDIES OF SUGAR CANE VARIETIESGROWING IN DIFFERENT SOIL TYPES.C. MONGELARD & E. ROCHECOUSTEInvestigations on the comparative developmentof root systems of sugar cane vanetiesgrowing in different soil types were started thisyear. The object was to determine the growthresponse of root systems of the same varietyand also of different varieties to differentconditions of soil, climate and fertilizer treatment.The excavation technique of LEE (1926)which consisted in determining root dryweight distribution in different layers of soilwas adopted in these studies.

-49-Root distribution of the variety M. 147/44was studied in the two soil types: low humiclatosol (Reduit and Pamplemousses) and darkmagnesium clay (Magenta), and that of thevariety Ebene 1/37 in the latosolic brownforest soil type (Union Park) and in the humicferruginous soil type (Belle Rive). The investigationswere carried out in first ratoon canes6 to 7 months old.ResultsThe general distribution of a root systemas determined by the excavation techniqueadopted is illustrated in fig. 16 for the varietyM. 147/44 grown at Reduit, From thisdiagram it will be observed that there is agreater root development in the row than inthe interrow at all depths along the profile.ExperimentalA 5 - foot cane row was selected in thefield and on either side all the roots under asurface area of 12! sq. ft. were removed frompre-determined layers of soil along the profile.In each operation a volume of soil 5 ft long by10 in. wide and 3 in. deep (see hatched portionin fig. 15) was carefully removed, placed on agunny bag and the roots sorted out. Theroots from each soil layer were then broughtto the laboratory and their volume determined;they were then oven - dried at 80 o e. Fourreplicate excavations were made for eachvariety growing in the different environmentalconditions.Fig. IS.Illustration of the digging procedure.Fig. 16.Block diagram to show distribution of root dry weightof the variety M.147/44 in measured volumes of soilin the Reduit locality.

- 50A linear relationship was found betweenmean volume and mean dry weight of rootseoc.for both varieties in the different soil types.The relationship for the variety M.147/44 isshown in fig. 17.Root distribution of the same variety wasfound to differ in the same soil type. For "0example, in the variety M. 147/44 the rootsystem at Pamp1emousses (fig. 18) did notpenetrate as deeply in the soil as it did atReduit (fig. 18). This was accounted for by the ~ JOOpresence of a hard soil pan at a depth of ~about 3 ft in the Pamplemousses soil type. In the ~dark magnesium clay soil, however, root distri- z 22 ,bution of the same variety, M. 147/44 was mainly :confined to the top 12 inches of soil. Thepeculiar root distribution of this variety at"0Magenta was attributed to the compact natureof this soil type.On the other hand, the variety Ebene 1/37"showed a greater development of roots in thesuperficial soil layers in the humic ferruginous osoil type at Belle Rive, whereas in the latosolicbrown forest soil type at Union Park a moreuniform root distribution was observed (fig.18).Fig. 17.10 ao JO -o so eo 10 80 QO 100 110 120 lJOMEAN DRY WEIGH! IN GRA~~Linear relationship between volume and dryweight of sugar cane roots (Data from varietyM.147j44 in Reduit soil type).REFERENCELEE, H. A. (1916). Progress report on the distribution of cane roots in the soil under plantationconditions. Hawaii Plant. Rec. 30: 511 - 19.

Fig. 18. R oot systems of sugar cane va rieties as seen ill soi l profile in different localiti es :(a) Parnplem ou sses (M 147144) (b) Reduit (M 147;44) (c) Belle Ri ve (Eh':ne 1/37)(d) Union Par k (E bene 1/ 37).

F ig. 19 Dwarf or multiple bud disease o n E .37 172

CANEDISEASESR. ANTOlNE & C. RICAUD*1. GENERAL CONSIDERATIONSEXPERIMENTAL work during the yearwas concentrated mainly on the twomajor pathological problems, ratoon stuntingand chlorotic streak.Minor outbreaks of other diseases wereobserved of which first mention should be madeof Cytospora rot (Cytospora sacchari Butler),recorded on a seedling cane at PamplemoussesExperiment Station as a new addition to thelist of diseases present in the island.The perfect stage of the red rot fungusiPhvsalospora tucumanensis Speg.) was observedfor the first time in lesions on midribs of leavesof the new variety Ebene 50/47. The peritheciadeveloped on leaves kept in a moist chamberand in cultures on corn meal agar.Several cases of pokkah-boeng tGlbberellamoniliformis (Sheldon) Wineland) were reportedduring the period of active growth, the diseasebeing more conspicuous on the variety Ebene 50/47.The attacks, however, were more spectacularthan dangerous although a few cases of toprot were observed.The promising cane M.81/52, particularlyadapted to the subhumid area, again showedacute symptoms of leaf scald (Xanthomonasalbilineans (Ash by) Dows.) in resistance trialsand experimental plots. The release of thevariety for cornrnercial plantings is unlikely.An outbreak of eye spot t Helmintliosporiumsacchari (Breda de Haan) Butler) was observedin a young plantation of Ebene 50/47 during thecooler months in the superhumid zone.The screening of pathogenic soil fungi wascontinued during the year and 200 isolatesobtained of which 60 have been identified. Asa corollary to the work, the rhizosphere ofplant, suspected of suffering from root disease,particularly the variety B.37172, is beingstudied.A spectacular, yet localized, attack of dwarfor multiple bud disease (fig. 19) was observedin plantings of B. 37172. It is contemplatedto study the etiology of the disease.2. RATOON STUNTING DISEASEThe resistance trials, as already reported,were badly damaged by the 1960 cyclones.The Parnplemousses trials are still standing butthe Belle Rive trial had to be replanted.Experimental results were obtained this year for1st and 3rd ratoons at Pamplernousses and forvirgins at Belle Rive. Table 14 gives a summaryof results obtained in the Pamplemoussesresistance trial planted in November, 1957.No data were collected in 1960.• C. Ricaud has contributed sections 5 and 6.

-52-Table 14.Summary of results obtained in a ratoon stunting disease triallaid down at Pamplernousses in 1957.TONS CANEjARPENT TONS SUGARjARPENTVarieties Crop Treated Untreated Reduction %Treated Untreated Reduction%Virgin 24.5 19.1 23 4.73 3.54 25M.134/32 1st ratoon 29.5 26.7 9 4.84 4.33 113rd 25.7 21.2 18 3.44 2.73 21Average 26.6 22.3 16 4.34 3.53 19Virgin 25.7 24.5 5 4.79 4.54 5M. 112/34 lst ratoon 36.9 29.4 20 5.90 4.49 243rd 26.7 25.4 5 3.39 3.23 5Average 29.8 26.4 11 4.69 4.09 13Virgin 33.7 29.3 13 6.26 5.39 14M.147/44 lst ratoon 38.6 35.9 7 5.74 5.62 23rd30.3 24.0 21 3.45 2.54 26"Average 34.2 29.7 13 5.15 4.52 12Virgin 34.3 28.5 17 5.91 4.95 16M.31/45 1st ratoon 39.6 35.2 11 6.41 5.55 133rd27.3 24.1 12 3.22 3.16 2"Average 33.7 29.3 13 5.18 4.55 12Virgin 24.5 21.9 11 4.65 3.81 18Ebene 1/37 1st ratoon 34.2 29.6 13 5.43 4.74 133rd28.4 23.2 18 3.64 3.04 16"Average 29.0 24.9 14 4.57 3.86 16Virgin 27.3 24.7 10 5.14 4.63 10B. 34104 1st ratoon 31.3 28.8 8 4.98 4.45 113rd28.3 24.4 14 3.45 2.83 18"Average 28.9 25.9 10 4.52 3.97 12Virgin 30.3 26.3 12 5.49 4.75 14B. 3337 lst Ratoon 37.5 34.2 9 6.14 5.30 143rd 30.1 26.8 11 3.04 3.11 2Average 32.6 29.1 11 4.89 4.39 10B.37161Virgin 23.1 17.1 26 4.17 3.02 281st ratoon 29.5 26.1 12 4.91 4.43 103rd 32.2 25.3 21 3.90 2.91 25---Average 28.3 22.8 19 4.33 3.45 20Virgin 31.5 28.0 11 5.79 5.19 10B.37172 1st ratoon 37.0 35.6 4 6.18 5.80 63rd 25.7 25.1 2 3.14 3.09 2Average 31.4 29.6 6 5.03 4.69 7

- 53--The results for 1st ratoons at Pamplemousses are given in Table 15.Table 15.Effects of ratoon stunting disease on yields in cane and sugarin 1st ratoons at Pamplemousses Experiment StationTONS CANEjARPENT TONS SUGARjARPENTUn- Reduc- Un- Reduc-Varieties Treated treated tion % Treated treated tion %M.202/46 30.4 26.8 12 3.89 3.16 19M.93/48 29.3 26.1 11 3.72 3.42 8M.253/48 36.0 34.0 6 4.46 4.25 STable 16 gives the results for virgins in the superhumid zone.Table 16.Effects of ratoon stunting disease on yields in cane and sugar in virgins atBelle Rive Experiment StationTONS CANEjARPENT TONS SUGARjARPENTUn- Reduc- Un- Reduc-Varieties Treated treated tion % Treated treated tion %M.147/44 29.2 23.8 18 3.42 2.78 19M.31/45 16.2 12.2 25 1.85 1.35 27M.202/46 30.8 19.2 38 3.73 2.19 41M.93/48 19.6 15.8 19 2.29 1.80 21M.253/48 19.6 17.0 13 2.31 2.04 12Ebene 1/37 27.2 24.0 12 3.43 3.05 IIEbene 50/47 31.6 24.8 22 4.65 3.37 28B.3337 21.6 19.0 12 2.64 2.32 12B.37172 20.6 17.8 14 2.74 2.40 12The average reduction in yield of sugar forvirgins, Ist and 3rd ratoons at Pamplemoussesranged from 7% in B. 37172 to 20% in B.37161.The varieties released more recently showedreductions in yield of sugar for 1st ratoons, inthe same locality, varying from 5 % in M.253/48to 19% in M. 202/46. In the superhumidzone, in virgins, losses have fluctuated between11% in Ebene 1/37 and 41 % in M. 202/46.The results confirm the observation that thedisease is more damaging in the superhumidzone.3. HEAT TREATMENT OF CUTTINGSThe central hot water treatment installationat Belle Rive worked fairly smoothly duringthe first part of the year, but later the plantoperated well below capacity with the resultthat 2,456 tons of cuttings were treated in 1961.The good germination obtained early in theyear was followed in certain cases by severefailures which may be attributed mainly toabnormally wet conditions at planting time.The result was that heavy recruitings had to bemade and in the end only 375 arpents ofnurseries were planted, giving the unusuallyhigh rate of 6.5 tons of cuttings per arpent.Of that area, 65 % or 243 acres of nurserieswere maintained in order to provide healthymaterial for the 1962 plantings (Table 17).

-54-Table 17. Nurseries established in 1961.East-CentreWestSouthNorthTotalSectorArea planted Area maintained Area maintained %(Arpents)(Arpents)102 62 6142 23 55116 66 57115 92 80375 243 65The varietal composition of nursenes established in 1961 is given III Table 18.Table 18. Varieties established in nurseries in 1961.Area planted Area maintained Area maintained 0/10Variety (Arpents) (Arpents)M.147/44 121.9 86.5 71.0M.202/46 64.0 42.9 67.0B.37172 48.2 44.7 92.7M.93/48 33.6 10.5 31.2M.253/48 33.5 16.7 49.8Ebene 1/37 30.8 15.0 48.7B. 34104 15.8 11.0 69.6Ebene 50/47 9.5 4.5 47.4M.134/32 8.0 5.8 72.5B. 3337 5.2 0.7 13.5M.31/45 4.4 3.4 77.3M.305/49 0.5 0.5 100.0R.397 0.5 0.5 100.0Total 375.9 242.7 64.8In an attempt to intensify the campaignagainst ratoon stunting disease, a scheme forthe establishment of a central nursery is atpresent under study.provided would servenurseries on estates.The healthy stockfor planting secondary4. CHLOROTIC STREAKThe short hot water treatment of cuttingsonly mitigates the effects of chlorotic streak,which is still the major disease of the highrainfall region and which, although absentgenerally from drier areas, prevails in somerestricted localities on heavy soils with poordrainage. Although the heat-treatment inactivatesthe pathogen in the cutting, the stoolderived from such cutting will, when planted inan area in which the disease prevails, be liableto infection.Results from previous work having shownthat chlorotic streak is apparently transmittedin the soil and that contaminated water couldbe infective, investigations were pursued in anattempt to elucidate the factors involved in thetransmission of the disease.Canes derived from heat-treated cuttings,

Fig 20 Insect-pr oof ca ges fo r the study of t !J ~ ~ r;: " . " :: n j s s l o n of chlorot ic strea k.

Fig . 2] .Perfect stage of the red rot fungus iPh ysalosoora tucuman ensis Speg.)Top .Cr oss secti on of perithecrurn.Bottom ASCI and ascospores in , cru shed pcrirh eciurn .

-55-obtained from an apparently disease-free area,are grown in concrete containers under insectproofindividual cages (fig. 20). The soilmedium was either (a) unsterilized from adiseased area or (b) sterilized by heat andfumigated. The sterilized soil was (i) left assuch, to provide the healthy control, (ii)watered with filtered leachate from an infectedsoil and (iii) watered with unfiltered leachate.Infected cuttings planted in unsterilized soil,to provide the diseased control, grew relativelywell and showed abundant leaf symptoms underthe conditions of the experiment.The nematode fauna of the soil in thecontainers is being regularly assessed. Theresults from the experiment will be submittedfor publication elsewhere.As it seems reasonable to assume thatchlorotic streak is transmitted in the soil, thetask of controlling the disease appears moredifficult. In Mauritius, the high number ofratoons taken further complicates the problemand it seems that, in order to combat the diseaseefficiently, a direct approach to the production ofresistant varieties will have to be made. Withthat aim in view, the reactions to the diseaseof all breeding canes used in Mauritius arebeing assessed.The attention of planters is once moredrawn to the high susceptibility of M.253/48,a variety which, although cultivated in the subhumidarea, has to be given the short hotwater treatment whenever euttings cannot beobtained from healthy fields.5. RED ROTRed rot lesions are very common on themidribs of the leaves of the variety Ebene 50/47.Affected leaf portions were collected fromvarious localities, during a survey of thevariety and kept in a humidity chamber. After10 to 15 days, numerous small black peritheciahad developed in the dried-up leaves.The perithecia were embedded in the leafblade with the ostioles protruding through bothlower and upper epidermis. They were alsopresent in the midrib. Others, more conspicuous,were on the surface of the leaf tissue,having developed from the aerial myceliumproduced in the moist atmosphere.The perithecia were sub-spherical, averagingin size B8!! X 102!!. The asci measured51!! x II!! and the ascospores 18!! X 6!!. (fig. 21).Examinations of old, drying-up leaves ofEbene 50/47 bearing the characteristic lesionson the midribs and also of the trash failed toreveal the production of perithecia in thefield. Furthermore, the midrib lesions of leaves ofEbene 50/47 did not always produce perithecia,when kept in the humidity chamber. Similarmaterial collected from leaves of B.3337, avariety which also shows abundant leaf lesions,failed to give fructifications.The red rot fungus, Physalospora tucumanensisSpeg.. being homothallic. it may be that certainconditions in the host plant interfere with theproduction of the perithecia. That wouldaccount for their presence in one varietyalone. That assumption together with theinconspicuous nature of the perithecia producedin the dried-up leaves and trash,would probably explain the failure in thepast to discover the perfect stage of the fungusin Mauritius.Peritheeia were also obtained on corn mealagar cultures made by streaking conidia prickedoff acervuli on material that produced peritheciain moist chamber. Cultures made onpotato carrot agar and Wilbrink's medium didnot yield fructifications. Measurements of theperithecia, asci and ascospores, whether obtainedin culture or leaf lesions, agreed with thosereported from other sugar cane countries forP. tucumanensis.6. A METHOD FOR INOCULATING LEA..' SCALD IN FIELD TRIALSIn leaf scald resistance trials, the assessmentof varieties generally involves the direct inoculationof the canes under test and the observationof their reaction. Suspensions of fresh culturesof the bacterium (Xanthomonas albilineans(Ash by) Dows.) usually enriched by a macerationof infected leaves and stalks providethe inoculum.

-56-Several methods have been used. Theyinvolve the inoculation of the sett or the growingstalk. Contamination of the sett is effectedby the cutting knife, by immersion in theinoculum or by injection under pressure. Thestalks are inoculated by means of a hypodermicsyringe just below the growing point or bysmearing with the inoculum and stabbing thestumps of freshly cut canes. The ratingsobtained in the trials have not always agreedwith the field reaction of the varieties. InMauritius, greater importance is attached toan assessment of the behaviour of new varietiesin pre-release trials established under differentclimatic and soil conditions. Resistance trialsare conducted in which four-row plots ofvarieties under test are flanked by inoculatedrows of susceptible cane. However, the methodused which consists in inoculating stumps offreshly cut canes has not resulted in a satisfactoryrate of infection. Such a conditionbeing essential in order to obtain reliableresults in the trial, experimentation has ledto the development of a new method ofinoculation with promising results.The inoculum was prepared by disintegratingleaves and stalks of infected cane in a Waringblender followed by maceration with sufficientwater for 6 hours. In the trial, the stalkswere cut just before the inoculation which wascarried out in the afternoon. All the shoots,mature stalks as well as tillers were cut, theformer at the base, the latter above the growingpoint. Inoculation was made by pouring theinoculum over the freshly cut surface whichwas then stabbed and covered with a pad ofcotton wool soaked in the inoculum. Theinoculated rows were then covered with trash.After a month, when the young ratoons haddeveloped, it was found that the rate ofinfection was exceptionally high. Examinationrevealed that infection was almost restricted tothe young tillers which had been cut andinoculated just above the growing point.Numerous characteristic white lines had developedfrom the cut end running right down theleaf. Similar results were obtained at threeexperiment stations under different climaticconditions.A second experiment was conducted at Reduitin order to test further the method of inoculation.Two rows, fifty feet long, ofthe susceptibleM .112/34, were inoculated in the stump of themature cane and in the yOUI1Ci tillers above thegrowing point, as described. After three weeks50 % of the shoots inoculttcd in the tillersshowed severe disease symptoms as comparedto 2 % in the stumps. Two months afterinoculation, the disease had become systemic in25 %ofthe inoculated tillers shown by sym ptomsin newly developed leaves, as compared to5% in stump inoculation.7. GUMMING DISEASEThe unusually dry conditions whichprevailed during the early part of the year mayhave been unfavourable to the spread of thegumming disease organism (Xanthomonasvasculorum (Cobb) Dows.). In the varietycollection, symptoms were rare in canes knownto be susceptible and developed unusually latein the resistance trial. Nine varieties showedsigns of gummosis and the promising ones willbe tested again.Gumming disease has been kept undercontrol in Mauritius through the cultivation ofresistant varieties. However, the existence ofdifferent strains of the pathogen and thepresence of the disease in various host plantsset an important problem which is now understudy in cooperation with the CommonwealthMycological Institute and pathologists inReunion, Madagascar and Natal.Following the discovery that sugar canevarieties reacted differently to infection underfield conditions in different countries and toinoculation with the pathogen from varioussources, Dr. A. C. Hayward, ofthe CommonwealthMycological Institute, has started a study ofXanthomonas vasculorum isolates obtained fromMauritius, Reunion, Madagascar and Natal.The results of these findings have been submittedfor publication in the Occasional PaperSeries of the M.S.I.R.I. Brief mention, however,will be made of his general conclusions.

-57-(a) X. vasculorum isolates from the sugarcane in Reunion and Mauritius are undistinguishableon the basis of morphological andphysiological properties. They can be differentiatedby host reaction.(b) Isolates from Reunion and Mauritiuson the one hand differ in cultural and physiologicalcharacteristics from those obtained fromNatal, Southern Rhodesia and Madagascar onthe other. These appear to be geographicalvariants as distinct from variants whichdiffer only in pathogenicity or virulence.(c) There are two distinct populations ofbacteria in Mauritius: one causing gurnmosis ofthe sugar cane and the other the endemicdisease on Thysanolaena maxima which had beenattributed to the sugar cane gumming diseasepathogen. The affinity of the sugar canestrain for T. maxima is probably very low, theconverse being equally true.(d) Unlike Mauritius, Reunion has noendemic disease of T. maxima. The diseaseresembling gumrnosis on T. maxima in Reunion,which was reported only once, was due to thesugar cane strain of X. vasculorum; the cyclonicconditions which had prevailed had probablyinduced the temporary passage of the pathogenfrom cane to T. maxima.8. FIJI DISEASE IN MADAGASCARFinal results have been obtained in ratoonsin the first trial established at Brickaville, onthe East Coast of Madagascar, in 1959 inco-operation with the lnstitut de RechercheAgronomique de Madagascar.The assessment is as follows:(a) Very highly susceptible (- -)M. 134/32, Q. 42, B. 37172, Pepecuca,B.34104, PR. 1000, N : Co. 310, Q.49.(b) Highly susceptible (-)Q.47, P.O.].2878, M. 147/44.(c) Moderately susceptible to moderatelyresistant (= - to = -l-)B.3337, B. 37161, Atlas, Vesta,(d) Highly resistant (+)R. 366, R. 383.(e) Very highly resistant (++)Pindar, Q.57, S. 17, M.31/45, Ragnar,Trojan.It will be noted that, of all the varietieswhich have been tested, M. 31/45 is the only oneof the commercially important canes in Mauritiusto have reacted as resistant to the disease,As the cane has also shown resistance to thestrain of the gumming disease pathogen inReunion Island. the cultivation of that variety,even on a limited scale, should be continued.The variety M. 112/34 is being tested in thesecond t -;;:1 planted in J .ily, 1960. The experimenthac, been harvested and results will beavailable in 1962. M.202/46, M. 93/48 and Ebene1/37 are at present in the third trial plantedin December 1961 and M. 253/48 and Ebene50/47 arc undergoing quarantine in Madagascarand will be included in the fourth trial scheduledto be planted in November, 1962.After the discovery of Fiji disease on theeast coast of Madagascar, several measureswere adopted by the authorities in that countryaiming at the protection of neighbouringcountries. One of the measures prohibited theentry and sale of the sugar cane in the town ofTamatave, consequently the port itself, fromwhich there is a regular shipping service toMauritius and Reunion islands.As nearly 3 tons of cane were being solddaily, for chewing purposes, in the markets ofTamatave, the authorities in Madagascar havebeen anxious for some time to have the prohibitionlifted. An agreement has now beenreached whereby the entry and sale of cane inthe town of Tamatavc will be authorized afterthe setting up of a control organization whose

-58-duties have been defined. The measuresinclude the registration of planters authorizedto sell their canes in Tamatave, the entry andsale of the resistant variety Pindar alone in thetown and the maintenance of inspectionteams within the perimeter of the port ofTamatave, whose duty is to ensure that nopart of the sugar cane plant is taken into thatarea. The Governments of Mauritius andReunion have agreed to pay the expenses involvedin the control work.An accidental introduction of Fiji diseasein Mauritius would be a major catastrophe tothe sugar industry. The understanding andunfailing co-operation of the Minister for Agriculturein Madagascar is once more gratefullyacknowledged.

deFig 22f

-60-664 flies, all in good state and about half ofthem females, was released. The number offemale flies which had mated before theirrelease is not known but all had been retainedin organdie cages with males for I to 5 days andmating was observed on several occasions.From October onwards, periodic attempts weremade to recover the parasite, by searching forthe adults and by collecting borers, but none hadbeen found by the end of the year and it isnot known if the insect is established.Breeding the parasite in the laboratory wasbegun in July with the object of maintaining aculture which could provide more flies forrelease in the field. Meanwhile, efforts toestablish laboratory cultures were also beingmade at the e.I.B.e. stations in Pakistan,India and Trinidad, using material received fromJava.At the outset of this work, details of thebiology of Diatraeophaga were not knownalthough the insect was presumed to be aIarvipositing form with a similar life-cycle toLixophaga and the other Neotropical Taehinidparasites of Diatraea. This proved to be soand the well-known breeding technique used forthese species was employed successfully. However,although a laboratory culture was establishedand was in its 4th generation at the endof the year, the insect has not been easy to breedand the culture could not be built up sufficientlyto provide flies for release in the field.Efforts to improve the breeding technique arccontinuing, particularly in view of the factthat the fate of the flies originally released isuncertain and further liberations may benecessary to establish the insect in the field.The main difficulty encountered during breedingis the reluctance of the flies to mate in captivity,a factor which led to the failure ofculturesinitiated at the e.B.l.e. stations mentionedabove.The salient features of the life cycle ofDiatraeophaga and of the breeding techniqueemployed are as follows. The adults, whichusually emerge from the puparia before midday,are confined in organdie cages 2 ft. squaresupplied with cane sugar and water. Otherfoods, e.g. honey, split canes, raisins, althoughoften provided, seem unnecessary. Warmthand sunshine activate the flies and they seemto mate more readily in strong, diffused sunlight.The females will mate shortly afteremergence, when the integument has hardened,and in the laboratory, at least, if they fail tomate within three days of emergence theygenerally will not mate at all. Mating lasts10 to 30 minutes and one mating apparentlyprovides all the sperm necessary to fertilize afemale's full complement of eggs. A gestationperiod of 6 to 9 days, depending upon temperature,follows mating and the female is thenready to begin deposition of eggs which hatchimmediately. Frequently however, a female willdeposit larvae which have hatched within itsbody. The deposition of eggs or larvae isstimulated by any surface or materials whichhave been in contact with a borer and a femalestimulated periodically will deposit its eggs orlarvae over a period of about three days. Forbreeding purposes, the young larvae wereobtained either by inducing a female to depositand later dissecting it to obtain any larvaeremaining in the utcrus or by retaining a matedfemale, without stimulating it, for 11 to 12 daysor until it died and then removing the uterus.About 300 young larvae may be obtained fromone female although in practice, as will bedescribed fully elsewhere, a proportion areoften lost as the procedure is delicate andrequires a certain amount of judgment. Oneto three parasite larvae arc placed on a borer,the number depending upon the size of thelatter. The «inoculated» borers are then placedseparately in plastic pill-boxes with pieces ofsugar cane and a little dry bagasse to absorbexcess moisture. Development of the parasitewithin the borer is completed 10 to 16 dayslater, according to temperature. The fullygrown parasite larva then leaves its host,whieh by that time has died, and pupates.The maximum number of parasites obtainedfrom one borer is three. Flies emerge fromthe puparia generally after 13 to 16 days sothat the complete life cycle, from mating ofthe parent flies to emergence of their adultprogeny, is about 30 and 45 days in the hotand cool seasons, respectively.

CANEPESTSJ. R. WILLIAMS1. THE STALK BORERIN accordance with the research programmeof the Institute, entomological work duringthe year was centred upon the stalk, orspotted, borer iProceras sacchariphagus Boj.).(a).Parasite introductionMuch use has been made in tropicalAmerica of Tachinid parasites to control stalkborers of the genus Diatraea but attempts madesome years ago to use the same species againstProceras in Mauritius were not successful,The only Tachinid fly known to attack Procerasnaturally is Diatraeophaga striatalis Towns. and,like its host, it is native to Java. Further, thisparasite does not apparently exist elsewhereand its introduction into Mauritius has beena long-desired experiment which was madepossible during the year through the assistanceof the Commonwealth Institute of BiologicalControl.Early in May, Or. M. A. Ghani of thePakistan station of the C.r.B.C. arrived in Javato collect Diatraeopltaga for despatch to Mauritius.Despite many difficulties, hc eventuallylocated a fairly good source of material in thevicinity of Pasuruan and between May 19thand July 7th sent a total of 3,918 field-collectedpuparia to Mauritius. In addition, specimensof other parasites which might be of futureinterest were collected and forwarded. Histask completed, Or. Ghani left Java in Augustand his very able services are gratefully acknowledged.Mortality of the insects during air transitbetween Java and Mauritius was unavoidablyhigh and accounted for about 70 % of thematerial sent. The greatest loss resulted fromemergence of flies from the puparia while enroute, a difficulty which could not be overcomesince the puparia, collected in the field, wereof different ages when despatched. The detailedresults of the air shipments were as followsNumber of shipments 25Number of puparia sent 3918Flies emerged and died in transit 1887Flies emerged in transit butreceived alivePuparia received intact7131318Flies emerged from abovepuparia 463Thus, a total of 1176 live flies were obtained,but some of those which had emerged in transitdied shortly after their receipt bringing thenumber down to approximately 850 flies whichcould be used for field Iibcrations and forbreeding in the laboratory.A cane field in the north, in a regionhighly infested with borers, was selected as asite to attempt colonization of thc parasiteand between June 15th and July 17th a total ofFig. 22. Characteristics of injury to sugar cane caused by the stalk borer, Proceras sacchariohoeus Boj.Young borer larvae feed upon the leaves and three types of leaf damage can be recognised - (a) boring intothe unrolled leaves of the spindle results in rows of holes across the leaf surface after the leaves expand,(b) patches are gnawed out of the upper leaf surface but the lower epidermis is left intact, (c) galleries in leafrnidribs may contain one or several larvae.Older borer larvae feed within the stalk ~ (d) they live only in the soft tissues (X) a little below the growingpoint (Y) in that part of the stem which is enveloped by the Jeaf sheaths. Stem deformities result as shown in(e) and (f). These comprise side shooting or sprouting of buds at or slightly below the damaged nodes (X), andconstriction of the stalk and shortening of the internodes at and above the injured point.

-61-(b)BiologyProgress was made with a study of thebiology of the moths of Proceras. The reproductivecapacities of the sexes are the featuresof adult life which have been under investigationand although this work, as yet incomplete,will form the su bject of a separate account, thefollowing summarizes some of the data obtainedto date.I. The moths, which are nocturnal, generallyemerge from the pupae within four hoursof sunset. They are not attracted by sugarymaterials, ordinary electric light or by mercuryvapour lamps.2. Mating may occur on the night ofemergence or during subsequent nights. Malesmay mate more than once during their lives;several were induced during experiments tomate twice, on successive nights, but nonecould be induced to mate for a third time,One mating appears always to provide a femalewith enough sperm to fertilize all her eggs,even if the male has mated before. Femalemoths, once melted, would not mate again.3. A female. at emergence, has very few orno ripe eggs in the ovaries but many ripenquickly and are ready for deposition on thefollowing night. The number of cccs=-=oneach successive night by a mated female islaidgoverned by the rate at whieh eggs ripen in theovaries. Normally, a female lays her fullcomplement of eggs within seven or eight daysof emergence and dies a day or two later.4. A female withholds her eggs if matingdoes not occur but if mating is delayed toolong the pressure of the accumulating ripeeggs in the ovaries forces her to deposit some ofthem. Such eggs are, of course, infertile.5. The total number of eggs laid by amoth varies considerably according to its sizeat emergence and by use of a regression equationit is possible to determine the avcrazenumber which will be laid by females of anygiven size.6. The moths have functional mouth partsand females require water to drink if they areto attain their maximum fecundicity. Food, inthe form of sugar, is not required and has noinfluence on fecundicity. Even without waterthe females are able to lay a considerablenumber of eggs, the fertility of which is notimpaired.7. The actual number of eggs laid byfemales of different sizes and under differentcircumstances cannot yet be quoted but theaverage number laid per female in the fieldis probably about 550.(c)Incidence of larval parasitesBoth items of work recounted abovenecessitated regular collections of Proceraslarvae and altogether about 8000 were obtainedfrom various localities during the year. Theopportunity of assessing larval parasitism in thefield was taken by recording thc number ofthese borers which were parasitized and theparasite species involved.Apanteles flavipes Cam. was found tobe the only common larval parasite and itsincidence was recorded on 3000 borers collectedduring the first six months of the year. Thepercentage of borers parasitized varied, witheach batch collected, from 0 to 50 o~ with anaverage of I0.7/~. There were no apparentdifferences in the incidence of parasitism frommonth to month, but on the other hand, borersoriginating from localities in the superhumidzone, mostly from Bclle Rive and Union Park,were consistently the most heavily parasitized.Apantelcs is evidently a parasite of much valuein cane fields particularly, it appears, in thesuperhumid zone.Other larval parasites were scarce and areapparently of little value. The parasitic nematodeworm, Mermis sp., was found only in threeborers. Agathis stigmatera (Cress.), an introducedspecies recovered for the first time fromProceras last year, as stated in the 1960 AnnualReport, was not found at all. Enicospilus sp., afairly common parasite of the pink boreriSesamiai, was found to occasionally attackProceras, contrary to previous belief.(d)Varietal resistanceThe intensity of stalk borer in varietiesEbene 50/47, M.202/46, M.93/48, and M. 253/48was observed in commereial plantations and invariety trials. Of these varieties. M. 202/46

-62-seems to be the least attacked by borers andcompared favourably with M. 147/44. M.253/48.on the other hand, is probably the most susceptibleof these varieties with Ebene 50/47 andM. 93/48 occupying intermediate positions.Including M. 147/44 and Ebene 1/37 as standards,the vaneucs arc provisionally placed inthe following order with regard to their relativeresistance to borer, beginning with the mostrcsistant : M.147/44, M. 202/46, Ebene 50/47,M.93/48, M.253/48, Ebene 1/37.2. THE PINK BORERVarious weeds, in and around cane fields,were examined early in the year to determinethe species which harbour the pink borer(Sesamia ea/amistis) and from which the insectmigrates to young sugar cane shoots. Anexhaustive search was not possible but the borerwas recorded from the following host-plants forthe first time :- Paspalum paniculatum Linn.(Herbe duvet), Paspalum conjugatum Berg. (Herbecreole), Paspa/um urvillei Stcnd. (Herbe codaya),Pennisetum purpureum Schurn. (Elephant grass),and Phalaris arundinacea Linn. (Herbe mackaye).The borer eggs, more difficult to find, wereseen only on the latter. The reported occurrenccof the borer in the following grasses wasconfirmed: Coix lachryma-jobi Linn. (Herbecollier), Panicum maximum Jacq. (Fataquc),Sorghum verticilliflorum Stend. (Millet sauvagc).A few small consignments of the Tachinidparasite, Sturmiopsis inferens Tns., were receivedfrom the Indian station of the CommonwealthInstitute of Biological Control. Theflies were released in the field but it is improbablethat the number released is enough toenable the insect to establish itself. It is hopedto obtain more material of this species.3. ARMY WORMSFor the third successive year, after a periodof nine years without reported attacks, armyworms appeared in several cane fields, all inthe south of the island. The circumstances ofthe outbreaks were similar to those whichoccurred in 1959 and 1960. It is now thoughtthat the attraction of moths to burnt fields isdue to the strong smell of fermentation whichusually persists in the fields for some daysafter burning and emanates from cut stumpsand rejected stalks lying on thc ground. Theattractiveness of fermenting materials to nightflying moths is well known to lepidopterists whomake such use of a technique called «sugaring».This consists of smearing fermenting mixturesof syrup, rotten fruit, stale beer, etc. on fencesor tree trunks to attact nocturnal lepidoptera,notably Noctuid moths. It seems that burninga cane field inadvertently results in «sugaring»on a large scale causing a concentration ofarmy worm moths which happen to be in thevicinity.It is not considered that complete defoliationof ratoon cane when 3 to 5 weeks old hasany appreciable effect on ultimate cane yield.However, this point needs to be ascertainedand some replicated plot experiments are inprogress.4. MISCELLANEOUSThe despatch of Apanteles fiavipes Cam.to Madagascar, begun in December 1960, atthe desire of the lnstitut de Recherches Agronomiquesde Madagascar was discontinued inJuly. During this period, 45 consignments comprisingabout 17,000 cocoons were sent by air.It is believed that the parasite has now becomeestablished on Proceras sacchariphagus in theregion of Ambilobe.

WEEDCONTROLE. ROCHECOUSTE1. HERBICIDAL VALUE OF SUBSTITUTED UREASThe substituted ureas DCMU (Karmex)and CMU (Telvar) and the triazine compoundsSimazine and Atrazine (5 Ib) were used aloneand in combination with sodium chlorate(10 lb) and TCA (10 lb) and were compared toa standard formulation consisting of an MCPAor 2, 4-D derivative (4 lb a.e.) TCA (10 lb)and sodium chlorate (10 lb). The herbicideswere applied in pre-emergence spray about aweek after planting at the above rates of thecommercial product per arpent. The experi-AND TRIAZINE COMPOUNDS IN THE HUMID AND SUBHUMID AREASFOLLOWING up the work carried out in ments were conducted in non-irrigated fieldsthe superhumid areas with the substituted as well as in fields with surface or overheadureas DCMU and CMU and the triazine irrigation. Weed assessment was made by thecompounds Simazine and Atrazine, experiments frequency-abundance method 4 months afterwere laid down with these chemicals this year in herbicide application.the humid and subhumid areas of the island. Itmust be observed, however, that in these Ratoon Canesregions chemical weed control is of lesserimportance than m the superhumid zone. In ratoon canes the substituted ureas DCMUThe main reasons are (i) the canes shade and CMU and the triazine compounds Simazinethe interlines fairly rapidly thus selling up and Atrazine (2 - 3 lb) were used in combinationwith sodium chlorate (2 - 3 lb) and TCAconditions unsuitable to weed growth, (ii) thetrash lined up on the interlincs after harvest (5 Ib) and were compared to a standard formulationconsisting of an MCPA or 2, 4-Dassists in controlling the establishment of weedsowing to its slow decay.derivative (2 Ib a.e.), sodium chlorate (2 - 3 lb.)The object of these trials was to determine and TCA (5 lb). Rates of application werewhether in these drier areas the use of herbicidesof low solubility such as the substituted of ratoon canes and weed assessment was madein pounds of the commercial product per arpentureas and the triazine compounds would not by the frequency-abundance method 3 monthsprove an economic proposition in comparison after herbicide application. In these experimentsthe trash was lined up on alternateto the synthetic plant growth regulators MCPAand 2, 4 - D. Investigations were carried out interlines and the herbicides applied on thein plant canes and ratoon canes.cane rows and on the interlines free of trash.Plant CanesResultsIn plant canes although differences wereobserved between the individual treatments yeton the average the substituted ureas DCMUand CMU and the triazine compounds Simazineand Atrazine gave very comparable results.Further it was found that the addition ofsodium chlorate and TCA to these hei bicidesdid not consistently improve their efficacy. Inratoon canes, a relatively similar observationwas recorded.

-64-Effects on weedsPerennial weeds were in general not affectedby the different treatments and the high sconngin some of the plots was mainly due to thepresenee of perennials such as Oxalis dcbilis,Cyperus rotundus and Paederia fartida. Annualgrasses were in general better controlled byDCMU and of these Panicum maximum andBrachiaria reptails may be mentioned. Ofthe broad leaved annuals, Plantago lanccolataand Argemone mexicana were the least affectedby the different treatments.ConclusionsExperimental work with the substitutedureas DCMU and CMU and the triazine cornpoundsSimazine and Atrazine in the humid andsubhurnid sugar cane zones has shown thatthese herbicides were not consistently betterthan a formulation collsisting of an MCPA or2, 4-D derivative, TCA and sodium chlorate.Such an observation is of importance for itindicates that the use of these chemicalsin those areas where rainfall is inadequate mayprove uneconomic unless the aim in view isto eradicate a specific annual resistant to theMCPA and 2, 4-D derivatives.From an economic view point, however, itmust not be overlooked that during the warmwet season, January to March, when rainfallis not deficient, the use of these herbicides inthe humid and subhumid areas may give verysatisfactory results.Table 19.Comparative efficacy of substituted urcas and triazine compounds in plant canes(4 months after herbicide application)TREATMENTS WEED INFESTATION ~; STANDARD FORMULATION(Rates in Ib of the commercial product perarpent in 60 gallons of water) Surface Irrigated Overhead Irrigated Non IrrigatedLocality Locality LocalityMedjne Arnitie CascadeLocalitySI.AntoineLocalityBelOmbreLocalityCreveCoeurCMUDCMUSimazineAtrazineCMUDCMUSimazineAtrazineCMUDCMUSimazineAtrazineCMUDCMUSirnazineAtrazine(5)(5)(5)(5)(5) + Sodium Chlorate (10)(5) + Sodium Chlorutc (10)(5) + Sodium Chlorate (10)(5) + Sodium Chlorate (l0)(5) + TCA (l0)(5) + TCA (l0)(5) + TCA (10)(5) -] TCA (l0)(5) + TCA (l0) + Sodium Chlorate (10)(5) -t- TeA (IO) + Sodium Chlorate (l0) _(5) + TCA (10)1 Sodium Chloratc (10) _(5) + TCA (10) -e Sodium Chlorate (10) _403957573750967863746483591028552 17060 9857 9850 8647 4260 4870 19052 12552 9055 9447 7037 86436572454036604932184338293835259575998349485265534644493533657397516811981111544097785977RAINFALLTotal rainfall (inches) during experimentNo. of rainy days3.17213.72261.71278.205413.504512.1436IRRIGATIONSurface (4) - 2 inches per irrigation at monthlyintervals8.08.0Overhead (8) -I inch per irrigation at fortnightlyintervals8.08.0RAINFALL + IRRIGATIONIU711.729.7116.2013.5012.14

-65-Table 20.Comparative efficacy of substituted ureas and triazine compounds in ratoon canes(3 months after herbicide applicalion)TREATMENTS(Rate in Ib of the commercial product per arpcntWEED INFESTATION % STANDARD FORMULATIONLOCALITIESin 60 gallons of water) Union Ducray Union Ducray Terracine Terracine(I) (2) (I) (2)CMU (3) + Sodium Chlorate (3) 67 64 54 55DCMU (3) ,. Sodium Chlorate (3) 84 52 69 17Simazine (3) + Sodium Chlorate (3) 96 120 64 23Atrazine (3) + Sodium Chlorale (3) 104 104 120 27CMU (2) + Sodium Chlorate (2) 88 100 105 39DCMU (2) + Sodium Chlorate (2) 80 48 82 33Simazine (2) + Sodium Chlorate (2) 80 lOO 115 39Atrazine (2) + Sodium Chlorate (2) 92 124 136 37CMU (2) + Sodium Chloratc (2) + TCA (5) 68 56 67 27DCMU (2) + Sodium Chloratc (2) -! TCA (5) 48 36 64 30Sirnazine (2) + Sodium Chlorate (2) + TCA (5) 60 60 113 47Atrazine (2) + Sodium Chlorate (2) + TCA (5) 56 56 95 47RAINFALLTotal rainfall (inches) during experiment 9.84 8.08 6.59 10.64No. of rainy days 32 33 31 442. EVALUATION OF NEW HERBICIDESdescribed elsewhere by the writer (1959).Results and conclusionsThe logarithmic spraying technique hasbeen adopted by the Institute for the evaluationof new herbicides because useful informationcan be obtained by this method in a relativelyshort time both with regard to the weedsand crop.Two logarithmic trials were laid down thisyear with Prometone 2A-bis (isopropylamino)- 6 - mcthoxy - 1,3,5 triazine and ParaquatI, 1 1 -- dimethyl 4, 4 1 bipyridylium di (methylsulphate) in post emergence application ofboth canes and weeds. The herbicides weresprayed in plant canes one and two months old,and before their application the weed populationon the logarithmic strips was assessed bythe frequency-abundance method. One monthafter spraying each 15 yards of logarithmicplot was subdivided into 3 yard sub-plots. Theeffects of the chemicals on the individual weedspecies were assessed in each plot by a pointssystem. The results obtained have been workedout in terms of 'overall effects' by the methodThe annuals predominant in the plots atthe time the sprayings were made were: Solanumnigrum, Digitaria timorensis. Ageratumconyzoides, Crepis japonica, Oxalis repens andPlantago lanceolata and of the perennials onlyKyllinga monocephala, Oxalis latifolia and Oxalisdebilis were fairly well distributed. At equivalentdosage rates Paraquat was found to bemore effective on the general weed populationthan Prometone (table 21). However, whilePrometone did not apparently affect canegrowth, Paraquat produced a scorching effecton the cane foliage characterized by irregularreddish brown spots. At the higher rates ofapplication, the herbicide caused more injuryto the canes than at the lower rates and itaffected one-month old canes more severelythan two-month old canes.REFERENCEROCHECOUSTE, E. (I959). Evaluating herbicides in sugar cane cultivation. Proc. int. Soc. Sug. Cone Tech.10: 549 - 55.

-66--Table 21. Effect of Prometone and Paraquat on weed infestation(Assessment of weed mortality - 4 weeks after treatment)Weeds: One month oldWeeds:Two months oldParaquatPrometoneTreatmentsMortality abundance ratingDosage range per arrent (lb active)per 3 yard logarithmic stripMortality abundance ratingDosage range per arpent Ob active)per :I yard logarithmic strip5.0--3.83.8-2.82.8-2.1 2.1-1.6 1.6--1.2 5.0-3.8 3.8--2.8 2.8-2.1 2.1-1.6 1.6-1.297.059.896.356.496.355.397.053.295.550.596.747.194.943.894.242.894.140.394.241.33. COMPARATIVE EFFECTIVENESS OF UROX, ATRATONE AND DCMU.The herbicides Urox (3(p-chlorophenyl)l,l-dimethylurea trichloroacetate), Atratone(2 - ethyl- amino - 4 - isopropylamino - 6 - methoxy­1,3,5 - triazine) and DCMU (N - (3, 4 - dichlorophenyl)W.N! - dimethyl urea) were evaluatedin pre-ernergence application at Belle Rive andUnion Park of the superhumid zone. Theywere applied at the rates of 2.4 and4.0 lb of active material per arpent just afterplanting and before weed emergence. Plotsize was 1/150 arpent and the treatments wererandomized with fourfold replications. Thecane cuttings of the variety Ebene 1/37 wereused and observations on cane germination andgrowth were made at regular intervals. Weedassessment was made by the frequency-abundancemethod 3 months after herbicide application.ResultsNo effect on cane germination was observedin all treatments and the chemicals did notapparently afTect cane growth. In both trialsDCMU proved more effective than Urox andAtratone at equivalent dosage rates of applications(table 22). On the other hand Urox andAtratone gave very comparable results. However,it must be observed that Oxalis repens, acommon annual of the superhumid localities,was more effectively controlled by Urox thanby Atratone.Table 22.Comparative effectiveness of Urox, Atratone and DCMU.Herbicides(Rates in Ib active per arpent)Weed Infestation % ControlLocalityBelle-RiveLocalityUnion-ParkUrox (4)Atratone (4)DCMU (4)Urox (2.4)Atratone (2.4)DCMU (2.4)62.565.625.064.178.153.131.444.019.842.649.531.0

CULTIVATION, IRRIGATION, CLIMATE1. COMPARATIVE STUDY OF SPRAY IRRIGATION AND SURFACEIRRIGATION ON GRAVELLY & FREE SOILSG. MAZERYTH IS experiment was initiated in 1957*,the required funds being provided at theearlier stages by Government and bythe Sugar Industry Reserve Fund. The sitefor the experiment was selected at Palmyre byarrangement with Medine S. E.The main object of the experiment was tocompare, under dry conditions, the merits ofoverheadand surface irrigation methods on latosolicreddish prairie - «gravelly soils»-and low humiclatosol - «free soils» - from the agronomicand economic standpoints and to determine therelative advantages of the fully portable and thesemi-permanent spraying systems.The original plan comprised an area ofabout 56 arpents in gravelly soils and 65arpents in free soils. Subsequently. however,it was found necessary to curtail these figuresto 47 arpents and 36 arpents respectively. Thischange in the experimental layout was madenecessary owing to the impossibility for thelimited spraying equipment available to copewith the work during the drier periods whenwater supply proved inadequate and longworking hours impracticable.Irrigation was started with the fully portableequipment in March 1958 on the gravellysoils and the semi-permanent installation threemonths later on the free soils.Frequency of irrigation depended on soilhumidity as determined by plaster of Paris cells.Sprayed plots received 2.5 inches of waterper irrigation. Surface irrigated plots receivedvarying amounts depending on soil types.During the course of the experiment, datawere collected 011 ~\ utcr co.is.nnption and costof the different systems of irrigation and, inaddition, meteorologic.•1 observations and growthmeasurements were recorded.I. Growth AspectsExploratory work in 1959 having shownthat optimum growth was obtained with spraysof about 2.5 inches of water per irrigation,this regime was maintained subsequently throughoutthe duration of the experiments.It will be observed (fig. 23) that on gravellysoils, spray irrigation has produced bettercane growth than surface irrigation. On freesoils, on the other hand, both methods ofirrigation were comparable (fig. 24).In general, surface irrigation and sprayirrigation had the same effect on cane yieldsas indicated by figures given in Table 23.• For a description of this experiment and equipment ,used, see AIlIl. Rep. ,If SI R.1., 1958, p, 82.

-68-Table 23.Tons cane per arpent* under spray and surface irrigation.Free SoilsGravelly Soils1958 1959 1961 Average 1958 1959 1961 AverageSpray Irrigation 33.6 41.0 38.3 37.6 27.7 29.1 30.5 29.1Surface 35.7 43.3 37.5 38.8 27.3 31.2 28.1 28.9• The cane yields have been corrected for initial fertility differences existing in the fields prior to experimentation.Gravelly soilsFree soils2 "12 ~1>0100~II ,'1>~x~200zz-~~z1>0'1>..... 100z~"z17'~~ "0z;ẓx1>x",'0'00" 0 'a 20 1> '0"1 I M e IN WEE KS7 ,°ID"TIME IN WEEKS20 10Fig. 23.Elongation. weekly intervalsDotted line: overhead irrigationPlain line: surface irrigationFig. 24.Elongation. weekly intervalsDotted line: overhead irrigationPlain line: surface irrigation2. Determination of Water Requirement(a) Bouyoucos Method. Plaster cells wereplaced in the experimental fields at depths of6 inches and 12 inches in order to use thevariations in soil moisture as a guide to irri-gat ion needs, It was observed that while therewas a elose relation between soil humidity ata depth of 6 inches and growth rate of thecanes, the soil moisture at 12 inches gave noindication as to the water requirement of theplant. In many cases, however, when the Bouyou-

-69-cos cells at a depth of 6" indicated 60 % availablemoisture, growth rate decreased, revealing awater shortage.Further studies are being carried out inorder to determine the depth at which theplaster cells should be placed in different soiltypes.Under local conditions, however, the use ofplaster cells in connection with large scaleirrigation schemes is of limited value due tothe fact that short inconspicuous leads have tobe used so as to reduce theft by field labourers,and this renders the regular moisture readingsdifficult for the irrigation officer.(b) Waler Balance Method. This methodis based on the assumption that water lost byevapotranspiration can be estimated by measuringthe evaporation from an open watersurface under similar conditions of environment.It is difficult to establish a correction factorfor converting the evaporation measurementsinto corresponding evapotranspiration becauseon one hand, the water removed from the soildepends on the physiological condition of theplant as well as on the coverage of the leafcanopy and, on the other hand, the evaporationfigures depend on the type of evaporimeterused.Comparative data have been obtained fromthree types of evaporimeters, viz. (I) the StandardTank of the Research Committee Institute ofCivil Engineers recommended by Penman;(2) the U. S. Weather Bureau Standard Tank(3) the «Irrigation Indicator» made by WrightRain Limited.On dry days, the evaporation obtainedfrom the Penman Evaporimeter varied from 85 ~~to 91 ~..~ of those obtained from the U. S.Standard Evaporimeter during the periodsJune - July and October - December respectively.During the same periods, the correspondingfigures obtained from the «Irrigation Indicator»have been 60 % and 50 % respectively. Thesedifferences may be due to the effect of wind onthe instruments which vary considerably Inshape, size and exposure.In principle, water should be added tomaximum field capacity when the water removedby evapotranspiration has brought theavailable moisture to 50 % maximum retentioncapacity, due allowance being made for therainfall during the period under consideration.However, it appears from the above that thistechnique needs further investigation before itspractical value can be assessed.3. Economics of the different Irrigation SystemsThe comparative costs of water applicationby means of semi-permanent and fully mobilespraying equipments are given in Table 24.Table 24.Cost of Spray irrigation.1. Depreciation of Diesel pumping unit2. Maintenance3. Fuel consumption ...4. Lubricating oil5. Depreciation of permanent equip.6. Depreciation of mobile equip.7. Labour including mechanic8. Cost of water valued Rs. 1.00/16000 cu. ft.TOTAL COST:Semi-PermanentSystemCost per arpent inchRs. c.122o 442 10o 32o 42o 70I 76o 247 20100% MobileSystemCost per arpent inchRs. c.I 56o 682 63o 39I 562 76o 249 82

-70--If allowance is made for the slightly lessefficient pumping unit used with the fullymobile equipment, the difference in favour ofthe semi-permanent system is brought from 36 %to about 29 %.The cost of surface irrigation has variedconsiderably from free soils to gravellysoils as illustrated by the following averagefigures (Table 25).Table 25.Cost of Surface Irrigation.Water required for one operator to work-cusecsArea irrigated by one operator in 8 hourswork arpentsWater applied per irrigation cu. ft. per arpentWater applied per irrigation -Number of irrigations per yearinchesCost of water valued at Rs. 1.00/16000 cu. ft.Rupees per arp. per yearCost of labour -Rupees per arp.Maintenance of channels - Rupees per arp. per yearTOTAL COST: Rupees per arp. per yearFree Soils1.0I.322.00061216.5031.2040.0087.70Gravelly Soils1.50.672.00019I149.5055.0040,00144.50It must be pointed out that the averagenumber of irrigations both overhead and surfacehas been on the low side due to the prolongeddrought experienced in 1961.The economics of various irrigation systemstried on free soils and on gravelly soils aresummarized in Table 26.Table26. Summary of Results.Free SoilsGravelly SoilsMethod of IrrigationSpray(semi-permanentequipment)SurfaceSpray(mobileequipment)SurfaceNumber of irrigations per year 12Total water applied - inches per year 30Cost of irrigation - rupees per yearper arp. 216.00Yield of cane - tons per arpent peryear 37.6Cost of irrigation - rupees per toncane 5.74127297.7038.82.26I128274.9629.19.451I209144.5028.95.00

-71-It will be observed from the above figuresthat while spray irrigation allows a considerablesaving of water, especially on gravelly soils,the higher cost of water application is notaccompanied by a corresponding increase incane yield.The value of spray irrigation in anyonecase depends therefore entirely on the specificconditions prevailing in that particular case.On free soils, when water is available, it isclear that surface irrigation is to be recommended.However, when land is available but wateris the limiting factor, spray irrigation offersa distinct advantage. Such conditions areencountered generally in the western part of theisland. On the very gravelly soils of thenorth and part of the eastern and southerncoasts, where plantations are often severelyaffected by drought, spray irrigation shouldprove economical especially when a cheapsource of energy is available.I wish to acknowledge the valuable cooperationof the Manager and Staff of MedincS.E. in all circumstances during the course ofthe experiment.2. NOTES ON CLIMATIC CONDITIONS OF THE 1961 CROP YEARPIERREHALAISThe meteorological data systematicallycollected during the last 13 years, at first onthree representative stations for the north,south and central sugar cane sectors wereextended as from November 1959 to all five,west, north, east, south and central sectors,thus covering more fully the whole sugar canearea of the island.The rainfall data have always been collectedon the same eighteen key stations.Minor corrections were applied to bringearlier temperature and wind recordings in linewith present day data.Figures 25 and 26 have been drawn to presenta continuous picture of the changes whichoccurred during the three critical four monthsperiods which constitute each yearly cropseason. A distinction is being shown betweenthe two sub periods of four months whichnormally make up tile eight months vegetativeperiod. This change in the presentation ofmeteorological data was thought adequate inorder to set off the particular conditions whichoccurred during 1961. The maturation periodextends from July to October.A close study of the figures demonstratesthat for the eleven consecutive years, that isbetween 1949 and 1959, no important changesrelative to air temperature and wind velocityoccurred. Consequently, moisture was thedominating factor in influencing cane and sugarproduction, as al ready stated in previous annualreports of the Institute.Those moisture l1uctuations, and theirconsequences on both cane tonnage and quality,should be considered as normal; however, thewhole picture was altered after 1960, whenwind and temperature changes brought abouta more confused situation which eventuallywill turn out to contribute to a much betterunderstanding of this complex problem.The crop year 1960 was dominated bydestructive cyclonic winds which caused considerabledamage to the canes as described atlength in last year's annual report of theInstitute.The first quarter of the 1961 crop seasonwas notable for one of the most severe summerdroughts in the history of Mauritius. Novemberto February rainfall only reached 12.5 inches

72>->t--'-cgow">>- -')0]100"zt­_z 5~O:E:~II-----------------=:-:-::-:::-~_o:..'=__------- - --- - - -- - --.- -~.:::15 -oU 210wc

:rwo.: 40~~a: . J S~X>""-c L JO2 520I S10oU~a:Z:J"":;:~a:~~ 0.L~>-2bO250240-'-'-c~Ẕc a:;,;5040JO20~o.~i J5~x> -c 30""L>- ~ 2 5>-",u=>00 20-,I~.> ~ J 50;:z z 10~~10-!-----,----,----'---,----.---.--·---,----.----r'---,---..,.---....,IIq4q 50 51 5 2 5 J 54 S5 5b 57 50bO~~UIzbO5040-'-':::zJO-ca:20+---.--~,------,-~--r-----------'------!---,-----,--------- -'_._-,---....,.----r--50 5 I 52 5J 54 55 5b 57 58 5q bO10Iq 4qFig. 26. Annual variations in rainfall, mean temperature and wind velocity. The average values for these factorsfrom 1949 to 1959 are indicated in dotted lines.A. First growth period. November 10 March.B. Second growth period. April to June..,I~bl

SUGARMANUFACTURE1. THE PERFORMANCE OF SUGAR FACTORIES IN 1961J. D. de R. de SAINT ANTOINE'WITH the closing down of Labourdonnais,only 23 factories were in operationin 1961. A synopsis of the chemicalcontrol figures of these factories is givenin tables XVII (i) - (v) of the Appendix.Cane and Sugar Production.In spite of a severe drought which prevailedduring the first months of the growing season,a record weight of cane amounting to close tofive million tons was harvested, partly as aresult of the late rains that fell during thematurity period. These late rains, however, had avery marked effect on cane quality so that thetonnage of sugar manufactured was some 28,000tons short of the 1959 record. Table 27gives the area harvested, cane crushed andsugar production figures for the past five years.Table 27.Area harvested (thousand arpents) cane crushed and sugar produced (thousand metric tons).1957 1958 1959 1960 1961*Area harvested 169.6 176.7 183.I 186.0 186.4Cane crushed 4,343.8 4,329.0 4,743.3 2,393.5 4,943.0Sugar produced98.5° Pol 562.0 525.8 581.0 236.1 553.4Cane Quality.As already pointed out. cane quality waspoor in 1961, averaging 12.81 for the islandas a whole, with a minimum figure of only11.65 recorded at one factory for the crop.The low sucrose content of the cane in 1961results not only from a wet maturity period butalso from the fact that a number of factorieshad to start crushing early in order to meetexport quotas. Thus, three factories startedlate in June and by the 15th of July thirteenwere m operation. Further, the duration ofthe crop was very long, averaging 123 days asagainst a figure of 108 days for the period1956-59; thus, whereas most factories normallyterminate their crop by the end of November,in 1961, eighteen factories were still crushingin December.Sucrose content ligures for the varioussectors of the island arc given in Table 28 forthe period 1957-61 whereas average fibre percent cane and mixed juice Gravity Purity forthe same period arc given in Table 29.• Provisional figures.

-75-Table 28. Sucrose per cent cane. 1957 - 61.Island West North East South Centre1957 14.59 14.87 15.53 14.33 14.16 14.331958 13.77 13.99 14.53 13.76 13.25 13.621959 13.76 14.09 14.67 13.66 13.23 13.661960 11.83 12.69 12.32 11.63 11.29 11.581961 12.81 13.06 13.46 12.53 12.42 12.91Table 29.Fibre per cent cane and mixed juiceGravity Purity, 1957-61.Mixed JuiceFibre % cane Gravity Purity1957 11.86 87.81958 12.21 87.21959 11.96 87.31960 14.38 83.51961 12.61 85.2The increase in fibre content from 12.0 forthe period 1957- 59 to 12.6 in 1961 may beattributed mainly to the crushing of an increasedtonnage of the high-fibre varieties M.147/44,B. 37172 and B. 3337. Table 30 shows thepercentages of the most important vanetiesharvested on estate lands in 1959 and 196I.Table 30. Percentage of varieties harvestedon estate lands, 1959 and 1961.Thus. of the two low-fibre varieties grownon a large scale, M.134/32 is losing groundyear after year, and the other, Ebene 1/37, ismore or less at a standstill, whereas the highfibre varieties are steadily gaining ground,M.147/44 in particular.Mixed juice purity was more than twounits lower than normal in 196I. Its influenceon boiling house work will be discussed later.Milling.1959M.134/32 33.8Ebene 1/37 28.0M.147/44 13.0B.37172 6.6B.3337 ... 5.0196118.127.021.410.57.7A synopsis of crushing data and millingfigures for the period 1957-61 is given inTable 31.Table 31. Milling results, 1957 - 61.No. of factoriesNo. of crushing daysNo. of net crushing hours/dayHours of stoppages/day"Time efficiencyTons cane/hourTons fibre/hourImbibition ~;; fibreSucrose ~.~ bagasseMoisture ~.~ bagasse ...Reduced mill extractionExtraction ratio1957 1958 195926 25 24105 108 11020.89 19.50 20.320.80 0.89 0.8296.3 95.6 96.176.1 82.5 87.79.03 10.07 10.49231 217 2302.63 2.50 2.3247.5 48.2 48.395.3 95.3 95.737.1 38.5 34.11960238914.920.5796.377.011.072092.2149.895.239.619612312318.860.8095.892.811.702222.0948.695.833.3• Exclusive of stoppages due to shortage of cane.

- 76--The 1961 crop was the longest obtainingfor a number of years, average number ofcrushing days per factory amounting to 123,with minimum and maximum figures of 83(Man Loisir) and 147 (Britannia) respectively.It should be pointed out that this long crop isnot so much the result of the record tonnageof cane harvested but of inadequate canesupply. Thus the number of net crushing hoursper day, exclusive of stoppages due to breakdowns,have dropped to a low 18.86 as againstan average of 20.24 for the period 1956-59.On the other hand, milling capacity keepsincreasing year after year, average metric tonsof cane ground per hour in 1961 havingamounted to 92.8, equivalent to 11.70 tons offibre per hour. Thus the situation is mostparadoxical since the main object of incurringheavy capital expenditure to increase millingcapacity is to reduce crop time and benefitfrom a higher average sucrose content of cane.It is also paradoxical that in an overcrowdedisland where the rate of increase of populationamounts to some 20,000 yearly, it should not bepossible to supply cane to factories more adequately.The problem is doubtless a complexone, but should be carefully studied. Reducingcrop time would not only cut down runningexpenses and result in greater benefit fromcapital expenditure incurred to increase factorycapacity, but would mean more sugar inthe bags, hence more money into the country.Milling work has been particularly good in1961, average reduced mill extraction recordedamounting to 95.8, corresponding to an extractionratio of 33.3. The best milling efficiencywas obtained at Riche en Eau with a reducedmill extraction of 97.1, whilst Beau Champ andThe Mount recorded 96.8. Bagasse moisturewas low on the average, with a minimum of45.90 at Riche en Eau, and eleven factoriesout of 23 recording less than 48 per cent moistureas against eight out of 24 in 1959 aud tenout of 25 in 1958.The Riviere imbibition system was used withsuccess at Belle Vue, Solitude and Union Flacqbut it was unfortunately not possible to assessexactly the benefits derived from the installation.Belle Vue, which did not operate in 1960,completed the installation of its milling tandemwhich now consists of two Fives-Cail andtwo Walkers uuits each independently driven bya steam turbine.ProcessingJuice clarificatio il was easy and caused noproblem in 1961. The first Prima-Jep clarifierto be installed in Mauritius functioned satisfactorilyat Belle Vue.Several more filter presses were replaced byrotary vacuum filters so that 17 factories outof 23 were equipped with the latter for thecrop. As a result, sucrose per cent cake andsucrose lost in cake per cent cane decreasedslightly as compared to the figures obtainedthe previous year. Yet, as already pointed outin the 1959 issue of this report, filter operationin Mauritius still suffers from inadequate controlin many factories. Thus, very few chemistscalculate filter retention and cannot thereforeevaluate filtration efficiency, It is with theobject of improving this situation that a study,which is published further in this report, wascarried out during the crop on the variousmethods that may be used for the determinationof retention.Boiling house work was a little better in1961 than in the previous years. As may beseen from Table 32, magma purity was higherand A-masseeuite purity was only 3.3 unitsbelow syrup purity, as against 7.0 for the period1957-59, indicating less boiling back. Puritydrops between massecuites and molasses werealso higher. Partly as a result ofthe installation,in many factories, of good low-head ealandria vacuumpans it was possible to boil heavy finalmassccuites of a high crystal content.Gravity purity of final molasses averaged35.7, the lowest figure on record to date. Itshould be pointed out, however, that the relativelyhigher reducing sugars content was conduciveto better exhaustion.It will be observed from Table 33 that,in spite of this lower purity, sucrose lossesin final molasses were higher in 1961 thanduring the previous years, disregarding theabnormal 1960 crop. This results from

-- 77--Table 32. Syrup, massecuites and molasses, 1957-61.1957 1958 1959 1960 1961Syrup purity 88.2 87.3 87.9 83.6 85.3A massecuite purity 79.6 81.0 81.7 79.7 82.0Purity drop, A. massecuite 20.7 20.8 20.1 20.6 22.3B. 21.1 20.8 21.1 19.5 22.2C. 22.3 22.7 23.6 21.6 24.6Crystal % Brix in C massecuite 33.4 34.1 35.3 33.2 36.0Magma purity 82.1 81.0 81.5 81.8 82.3Table 33. Final molasses, losses, and recoveries.1957 1958 1959 1960 1961Final molasses: Gravity purityRed. Sug. % BrixTot. Sug. % BrixWt. %cane @ 95° Brix ...Sucrose loss in final molasses % caneUndetermined losses %caneIndustrial losses % caneBoiling House RecoveryReduced Boiling House Recoverythe fact that, with the low mixed JUIce purityprevailing, molasses per cent cane was appreciablyhigher in 1961 than during the previousyears.For the first time in Mauritius, fully automatic48" x 30" centrifugals running at 1700R.P.M. were installed at Mon Loisir for thecuring of C massecuites. The machines,manufactured by ASEA - Landsverk are equippedwith Ward-Leonard drives. A series of experimentswere carried out during the crop withthem, the results of which will be publishedelsewhere*. However, a summary of theresults obtained is given in the introduction ofthis report.37.7 37.9 36.7 37.2 35.716.2 15.8 14.6 14.6 16.653.9 53.7 51.3 53.4 52.42.45 2.59 2.53 3.08 2.810.92 0.93 0.88 1.09 0.960.23 0.17 0.16 0.26 0.211.22 1.18 1.13 1.43 1.2491.3 91.1 91.4 87.1 89.989.0 89.3 89.6 88.5 89.7In at least two factories, froth fermentationcaused the loss of important quantities of finalmolasses in storage. The main reasons formolasses foaming are believed to be the useof excessive amounts of lime in clarification andof too high temperatures during the boiling ofthe final masseeuites. Hence the practice oftenresorted to of blowing steam into the molassesto facilitate pumping should be strongly condemned.Further, since the destruction ofseveral hundred tons of molasses represents animportant monetary loss, piping systems shouldbe installed in all storage tanks and compressedair blown through the molasses at regularintervals to keep foaming from setting in.REFERENCESSAINT ANTOINE, J. D. de R. and LAMUSSE J. P.(1959). The performance of sugar factories in 1959.Rep. Sag. Ind. Res. lIB I. Mauritius: 77-82.SAINT ANTOINE, J. D. de R. (1960). The performanceof sugar factories in 1960. Rep. Sug, Id. Res.Inst, Maurituis: 89-93.• Proceedings II Ih Congress, I.S.S.C.T.

--78-·-2. TWO-BOILING 'Is THREE-BOILING SYSTEMbyH, F, WIEHEWith a view to simplifying the boilingprocess and securing a better control over theboiling house operations, a two-boiling systemwas started in one of the sugar factories of theisland towards the end of the 1959 crop, Theprocess was studied more fully and followedthroughout the whole 1960 campaign duringwhieh the following average figures were obtained:SyrupA massecuiteA molassesC massecuiteFinal molassesBrix52,297.085,699,997.0Apparentpurity82,672.951.858,336,6Although simpler, the process adoptedproved less flexible and seemed to require moreequipment than the three-boiling system, Inspite of the high pan capacity of the factory,3.5 tons/TC.H., quite often bottle-necks occurredand the crushing rate had to be sloweddown to allow partial liquidation.The purpose of the present article is tostudy the equipment capacity involved for thetwo-boiling process adopted as compared tothat required for the three-boiling processnormally used in Mauritius,In Table 34 are given Brix and purity figuresfrom which a solids balance has been worked outfor each of the boiling schemes.Table 34.Average Brix and purity figures for the two-boiling and three-boiling systems.Three-boiling systemTwo-boiling systemBrixApparentpurityBrixApparentpuritySyrupA massecuitcA molassesB massecuiteB molassesC masseeuiteFinal molassesA & B sugarsC sugarMagma for A & B footingsSyrup and A molasses for C footings60959699878561704755319987876960 8796 734999 553199878769

-79-A summary of the solids balanceworked out for each of the systems is given hereunder.Table 35.Summary of solids balance.Three-boilingsystemTwo-boilingsystemKilos"solids in syrup" A rnassecuite" A molasses" B massecuite" B molasses" e masseeuite" Final molasses" A and B sugars100,000105,80038,90035,10019,60030,80017,60082,400100,000170,40088,60030,80017,60081,800Using the Brix figures given in Table 34 andassuming a specific weight of 40 kg/cu, ft. for A,Band e massecuites, the volumes of strikes tobe processed in the two boiling schemes cannow be calculated.(a) Three-boiling system· 105800Volume A massecuite =-- = 2784 cu.ft0.95x40· 35100Volume B massecuite = --- = 914 cu.ft.0.96x40· 30800Volume e massccuite = --- = 778 cu.ft,0.99x40(b) Two-boiling system4476 cu.ft.· 170400Volume A massecuite = ----- = 4438 cu.ft0.96x40Volume e rnassecuite =· 30800Assuming that the timestrike (including graining,steaming) is as follows:A massecuiteB massecuitee massecuite0.99x40Three-boilingsystem4 hours6 hours10 hours= 788 cu.ft,5216 cu.ft.required to boil adischarging andTwo-boilingsystem6 hours10 hoursthe number of strikes per pan per 24 hourswill be :(a)(b)Three-boiling system:A masseeuite 24 4 6B masseeuite : 24 6 4e masseeuite : 24 10 2.4Two-boiling system:A massecuite 24 6 4e massecuite : 24 10 2.4The pan capacity required for the twoprocesses can now be determined:(a) Three-boiling system :(b)A massecuite : 2784 -:- 6 = 464 cu. ft.B massecuite: 914 -:- 4 = 229 cu. ft.e massecuite: 778 -i- 2.4 = 324 cu. ft.Two-boiling system:1017 cu. ft.A massecuite : 4438 -i- 4 = 1110 cu. ft.e massecuite: 778 --'-- 2.4 = 324 cu. ft.1434 cu. ft.Additional pan capacity required for thetwo-boiling system as compared to the threeboilingsystem1434 - 1017xlOO 41%1017

- 80--Additional crystallizer and centrifugalcapacity required for the two-boiling system ascompared to the three-boiling system5216 - 44764476x 100 17%From the standpoint of equipment capacity,the above figures clearly show that the threeboilingprocess, as practised in Mauritius, ismore economical than the two-boiling processdiscussed above. This results from the factthat in the latter process the A massecuitepurity is only 73, as against a syrup purity of87. In other words. a considerable amount ofboiling back has to be resorted to.The question then arises whether it wouldbe practical and economical to adopt a twoboilingsystem when, as a result of unfavourableclimatic conditions for instance, the syruppurity is abnormally low, say, 82°. If the Amassecuite purity were to be kept at 73 as inthe two-boiling process discussed, the amount ofboiling back would no doubt be reduced. but itcan nevertheless be shown that, even then. theboiling scheme would require 20 /~ more pancapacity and 4 ~ ~ more crystallizer and centrifugalcapacity than the three-boiling system.On the other hand, it should be noted thatwith a syrup of low purity the two-boiling processmight prove beneficial if a first massecuite of80 instead of 73 purity were aimed at, beinggiven the appreciable reduction in boiling back.The main difficulty, however, would probablyreside in graining and building the final strikeon runnings of 56 purity assuming a purity dropof 24° between A massecuite and A molasses.Mention should here be made that such a schemehas already been studied by NOEL (1959) whohas shown that, apart from an increase in grainingtime of 15 to 20 ~,~, the use of molasses of56 - 57 purity as footing for the C massecuitewas not a serious drawback under the conditionsprevailing and with the equipment availableat St. Antoine factory in 1958.REFERE~CENOEL, R. (1959) The practical application of a straight two-boiling system. Pro r S. Agr. Sug: (Tech.)Ass. 33: 77 - 80.3. FILTERABILITY OF RAW SUGARE. C.VIGNESIntroductionThe filtcrability of a raw sugar is ofparticular interest to the refiner. Poor filteringsugars arc difficult and costly to refine. In thefirst place, they quickly bloek up filter pressesand, secondly, impair the rate of flow of liquorthrough char filters, resulting in loss of efficiency.All raw sugars contain a certain amount ofundesirable impurities. These occur as colloidmaterial or as particles too large to be trulycolloidal in nature. Some authorities believethat the filtration-impeding effect of theseparticles are primarily caused by their sizerather than their chemical nature. AI allevents, the percentage of insoluble solids has adirect bearing on the filtering characteristics ofraw sugar. The film of molasses surroundingsugar crystals does contain some of the unwantedconstituents but it is well known thatnon-sugars are fairly uniformly distributedthroughout the crystals as well. Althoughaffination removes the surface film, that part ofthe impurities which has found its way insidethe sugar crystal must be blamed for badfiltration.

-81-Non-sugars like silica, starch, gums, waxesetc. have all been described at some time orother as the cause of poor filterability. Theproblem has held the attention of sugar technologistsfor a long time but in spite of thelarge amount of research carried out so far,much of it is still not quite understood.The fact that raw sugar manufacturers cannotpredict the behaviour of their sugars underrefinery conditions constitutes a great handicap.Polarisation and ash content do not give anyindication. Very often good polarising sugarswith low ash give extremely troublesome melts.On the other hand, all the usual filterabilitytests arc of doubtful help in evaluating refiningqualities. The more commonly employed test,namely the EJliot test, is empirical and haslittle to recommend it. There is no satisfactoryevidence that it will give reliable and reproducibleresults when applied by different individualsto a variety of raw sugars. Moreover refiners,whether in U.K., U.S.A. or Australia, haveabandoned the method since, from their experience,it is of little value to refiners usinghigh efficiency affination machines and carbonatationplants.Therefore it is becoming increasingly clearthat a test, which will give filterability valuesin the laboratory having a satisfactory correlationwith refinery observations made onMauritius raws, must be found. With this aimin view the method, described by NICHOLSON& HORSLEY (1956), was selected as affordingthe greatest possibilities and investigated accordingly.This test has been claimed as being ofvalue in picking a sugar that is likely to filterbadly in a carbonatation process. Undoubtedlyit has certain obvious advantages over theElliot method; namely, the use of a definiteBrix, a pH close to that prevailing duringrefining and the use of a smaller amount offilter aid. These features simulating moreclosely the actual working conditions, it is notunreasonable to expect more realistic valuesof filterability. In particular, the smalleramount of filter aid is important, as in practiceit has been shown that large quantities tend toobscure differences in the behaviour of sugarsby "swamping" the effect of the impurities.The object of this study was to determinewhat faetor has the greatest influence on filtration.Accordingly, samples of export sugarswere examined for silica, starch, gums, wax andphosphates by well-known methods. The resultswere analysed statistically in an endeavourto determine the degree of correlation existingbetween filterability values and amounts ofspecific impurities. Finally, filterabilities, obtainedby both Elliot and Nicholson methods, werecompared.EXPERIMENTALEquipment.The apparatus has been described byNICHOLSON & HORSLEY (1956). Celite 505was used as filter-aid and calcium acetateethanolamine mixture as buffering agent. Thesyrup was filtered through a Whatrnan No. 54paper under a constant pressure of 50 lbs./sq. in.Filtration rates were reported as percentage ofthe rate for pure sugar syrup. Sufficient syrupwas used to fill the whole body ofthe apparatus.Following is a description of the actual workingconditions.ProcedureA mixture of 330 g. sugar and 220 m!.water is stirred until the sugar is completelydissolved. Brix is then adjusted to 60° using arefractometer and pH to 9.0 with calciumacetate/ethanolamine buffer using a glass electrode.The mixture is stirred for 3 minutes,left standing for 20 minutes, stirred again forone minute and poured into the apparatus.Next, the temperature of the mixture is taken,the head of the apparatus is screwed on andpressure applied. After allowing the filtrate torun to waste for the first 2 minutes, the filtrateflowing for the next 6 minutes is collected in agraduated cylinder, the volume collecting ineach minute interval being noted. Pressure isafterwards released, the head of the apparatusremoved and the temperature of the residualcontents of the filter taken. The rise foundin practice was never higher than 0.5°C.

-82-Filterability figures after 6, 7 and 8 minutes,at the average temperature of the test, weredetermined as described in the method. Thethree values obtained were averaged to give thefilterability of the raw sugar.CalibrationThis was carried out in a constant temperatureroom. The filter disc employed wascalibrated at three different temperatures,namely 20.1QC, 23.0°C and 25.1 QC using Tateand Lyle refined sugar. Calibration curveswere obtained by plotting volume of filtratecollected at the cnd of each minute againsttemperature. Straight lines were obtained.Reproducibility.The filtcrability of a sample of Mauritiusraw sugar was determined on nine differentoccasions and the following values found: 15.4,16.9, 15.2, 16.8, 15.5, 15.3, 15.1, 15.0, and 15.4giving an average of 15.6. The maximumdifference between two values is 1.9, in otherwords reproducibility is well within the 15%difference allowed by the method.Experimental DataFiltcrabilities, using the Nicholson method,were determined on all samples examined. Itwas possible to analyse only eleven samples fortheir phosphate content. Twelve other sampleswere available for the determination of wax andgums. In addition, Elliot filtcrability valueswere also obtained on these twelve samples.Twenty-one samples were examined for starchand thirty-two for silica. The results obtainedwere subjected to statistical analysis. All dataobtained arc shown in Tables 36 - 39.Since the suitability of a routine testdepends as much on its practicability as on itstechnical soundness, the time consumed duringthe test was carefully noted. From observationsmade, one worker supplied with the necessaryequipment can easily perform 8 to 10 determinationsper day.Methods of Analysis Followed.Wax - As described by BROWNE andZlRBAN in Sugar Analysis, 3rd.edition, p. 1092.Phosphate - The well known eolorimetriemethod using a Lumetron Colorimeter.Starch - The colorimctric method as describedin S.A.S. T.A. Proceedings,1954.Silica - The colorimetric method as describedin S.A.S.T.A. Proceedings,1957.Gums - As described by BROWNE andZERBAN in Sugar Analysis 3rd.edition, p. 1093.Results.Table 36.Effect of Starch on Filterability.Filterability Starch % Filterability Starch %(Nieholson)(Nichloson)28.4 0.0225 28.3 0.015023.7 0.0255 27.7 0.019535.8 0.0185 17.5 0.027533.6 0.0165 27.3 0.021529.5 0.0260 34.5 0.017516.2 0.0265 22.0 0.02154.1 0.0395 38.6 0.018519.7 0.0150 Il.l 0.02002.5 0.0280 17.0 0.031029.8 0.0135 32.1 0.021515.5 0.0240

-83-Table 37.Comparison between Filterabilities.Fi1terabilityFilterability(Nicholson)(Elliot)35.4 75.837.9 75.838.6 91.534.0 78.229.6 78.629.8 66.542.0 76.739.3 82.933.8 ~.937.6 M.628.0 80.829.8 68.7Gums and Wax content of Raw Sugars.Gums % Wax %0.10130.21930.12600.17130.12800.14600.16200.12330.24130.22800.25270.15130.01340.01220.00810.01160.01620.01170.00930.00630.01040.00560.00960.0064Table 38.Filterability(Nicholson)28.423.735.833.629.516.24.119.72.529.815.528.327.717.527.334.5Filterability and Silica Content of Raw Sugars.Silica %Filterability(Nicholson)0.013022.00.013838.60.0]]811.10.014532.10.013035.40.013837.90.010538.60.022034.00.015329.60.014929.80.011342.00.012139.30.012033.80.021537.60.018028.00.014029.8Silica %0.01100.01950.01460.01030.01050.0]]50.00750.01600.01550.01600.00850.01150.01500.00950.01400.0145Table 39. Filterability, Phosphate and Starch Content of Raw Sugars.Filterability Phosphate ppm Starch %(Nicholson)29.516.219.715.528.335.84.129.82.517.527.38.48.45.46.74.89.05.47.210.56.710.00.02600.02650.01500.02400.01500.01850.03950.01350.02800.02750.0215

--84 -Statistical analysis of results tabulatedgave the following relationships. Correlationcoefficient:(i) For 21 pairs between Filterability andStarch. r=0.645, significant at I % level.(ii) For 12 pairs:(a) Between Filterability and Gumsr=0.211, not significant.(b) Between Filterability and Waxr=0.344, not significant.(iii) For II pairs:(a) Between Filterability and Phosphate:r=0.144, not significant.(b) Between Starch and Phosphate:r=0.086. not significant.(iv) For 32 pairs between Filterability andSilica: r=0.248, not significant.Discussion.Data obtained reveal a direct relationshipbetween filtcrability and starch content. Therefore,the results of the present study lead usto believe that the latter is probably the maincause of bad filterability in Mauritius raws.This is precisely what had already been deducedfrom practical experience gained during refining.It would appear that filtration of melt, startsto give difficulties as soon as the amount ofstarch in the raw sugar reaches 150 ppm. Thedeterioration of local sugars coincides with theplanting of new varieties of cane rich in starchas reported by de SAINT ANTOINE and PARISH(1960). Other workers have also noted thatthere is a definite correlation between starchin sugars and filtering characteristics. ThusBUCHANAN (1959) finds that filtration ratevaries inversely with the concentration of starchin the sugar solution. According to this author,starch hinders filtration in two ways, namely byblocking of the filter cake by starch particlesand by exerting a viscosity effect duringfiltration. Moreover, starch has a stabilizingeffect on colloids as well as affecting the particlesize of calcium carbonate precipitate formedinside a sugar solution. Consequently, it isprobably no coincidence that raw sugars, e.g.from Natal and Australia, which have the reputationof being difficult to refine (BOYES,1958), also have starch contents of wellover 150 ppm. (INUMA, 1956, ALEXANDER,1957). In this connection, POWERS (1959)reports that cane varieties under certain climaticconditions retain a significant amount of starchdegradation products and yield raw sugarsgiving filtration difficulties to refiners usingcarbonatation; a considerable portion of thisimpurity occurs as inclusion inside the crystalitself, no amount of washing or affinationhaving any effect on the filterability.It will be noticed that no correlation hasbeen found between filterability and silica. Thisappears to be in opposition to conclusionsreached by certain authors (ALEXANDER,1957. CHU & CHU, 1961); but as pointedout by Douwrs DEKKER (1960), the difficulty inthe interpretation of results of various investigationsis that each worker uses his owntechnique and different techniques may showdifferent results.As was to be expected, a comparisonbetween Elliot and Nicholson tests shows noconstant factor to translate Elliot values intoNicholson values or vice versa.The results of the study reviewed aboveindicate that the Nicholson method of determiningfilterability of raw sugars is more reliablethan Elliot's method.The adoption of this method in Mauritiusshould result in a better assessment of therefining qualities of Mauritius raws.REFERENCESALEXANDER, J. B. (1957) - Some observations onthe filterability of Natal raw sugars. Proc,S. AIr. Tech. Ass., 3tst. Congress: 68-75.BOYES, P. N. (1958) - Quantitative determination ofsome non-sugars and partial removal of onein particular - Starch. Proc. S. AIr. Sag. Tech.AS5., 32nd. Congress: 37-43.BUCHANAN, E. J. (1959) - Recent observations onsugar cane starch and its effect on filterabilityof sugar. S. AIr. Sug, J.,42, (1): 32-47.CHU, J. F. & CHU, F. C. (1961) - A study of thefactors affecting the sugar filterability. TaiwanSugar, 8, (1): 18-23.DAVIS, C. W. (1959) - Filterability of raw sugar. lnt,SlIg. J., 61: 300-302.

Fig . 27. Isolates on osrnophilic aga r derived from : top - rnassecuite discharged from the vacuum pan (ba cterialcolonies on ly) ; bottom (yeast colonies), le}; - rnassecuite after cooling in the cr ysta llizer , righr- rawsugar.

Fig . 28. Yea st cells from raw sugar . (a) Saccharomyces rouxit (b) Torulopsts versa fills(c) Candida tropicalis (d) Schizosaccharomyces pombe.

-85--DOUWES OEKKER (1960) -- Report by SA SugarAssociation Delegates to the 1Oth Congress of111..:: International Society of Sugar C

-- 86 --5. CHEMICAL CONTROL NOTES(a). FLRTlIER STUDIES ON THE USE OF THE REFRACTOMETERFOR ROUTINE CHEMICAL CONTROLF. LE OUEN & M. RANDABELFollowing the preliminary work carried outby LAMUSSE (1960). it was decided to studymarc thoroughly the use of the refractometerinstead of hydrometers for the routine chemicalcontrol of sugar factories. The original projectwas to carry out parallel controls with therefractometer and the hydrometers in threefactories over the whole of the 1961 crushingseason. Unfortunately the Bausch and Lambprecision refractometcrs were not received untilthe early days of November when the crushingseason was nearly completed. Hence it waspossible to carry out parallel controls for onlyone week at Factory A, two weeks at Factory Band four weeks at Factory C.Comparisons were made during theseperiods with first expressed juice, mixed JUiceand final molasses, The analytical methods usedfor the dcnsimctric Brix and sucrose determinationswere the standard ones followed inMauritius for routine chemical control. Forthe determination of refractometer Brixes andcorresponding sucrose determinations in molasses,the methods adopted were those used in Hawaiiand described in the Official Methods of theHawaiian Sugar Technologists for Routine Controlof Cane Sugar Factories, The Hawaiian methodof determining sucrose in juices differs verylittle from that used in Mauritius sinee in thecase of juices no dilution is necessary. Itwas therefore deemed preferable for the purposeof the experiment to use the latter methodwhich involves the removal of excess leadwith potassium oxalate.The results of these analyses are publishedin Table 40 from which it may be seen thatthe refractometer Brix is usually lower than thedensimetric Brix and hence the sucrose valuecalculated from the pol reading and the refractometerBrix is usually slightly larger than theTable 40.Comparison of Brix, Sucrose and Purity Values obtained with densimetric and refractometer controls.First Expressed Juice Mixed Juice Final MolassesFACTORY A B C A B C A B CPER[OD [ week 2 weeks 3~ weeks 1 week 2 weeks 4 weeks week 2 weeks 4 weeksNo. of samples for Brix 45 137 329 45 137 368 9 11 18Range of differences in Brix(Rcf-Dens) ... -0.02 to -10.38 to -;-2.[4 to -0.02 to -0-0.80to +1.51 to -3.3 to -6.2 to -3.1 to-0.91 -0.85 -2.09 -0.87 -0.98 -1.84 -8.0 -8.5 -10.7Mean dcnsimctric Brix: 20.35 20.!7 21.03 14.85 14.22 15.7[ 96.0 96.1 97.0Mean refractometer Brix 19.98 19.97 20.53 14.56 14.02 15.46 88.85 88.17 89.61No. of samples for Sucrose~~ gm. 6- 12- 23- 6- 12- 23- 9 ][ 18Range of differences inSucrose /~ gm (Rcf-Dens) 0.02 to 0.00 to 0.02 to O.O! to 0.01 to 0.00 to -0.20 to -[.48 to -1.90 to0.04 0.03 0,07 0.Q3 0.02 0.04 -1.80 -1 1.66 -;-2.][Mean dcnsimetric Sucrose/~ gm 17.92 18.01 18.42 12.88 12.41 13.40 31.20 34.62 34.85Mean refractometer Sucrose0() gm [7.95 18.03 18.45 12.89 12.42 [3.41 30.37 34.21 34.87Range of differences inPurity (Ref-Dcns.) 1.5 to 0.6 to 0.9 to 1.5 to I.l to 0.4 to 0.6to 1.4 to -0.1 to2.[ 1.6 3.0 2.1 2.1 3.5 2.7 4.8 6.0Mean densimctric purity 88.1 89.3 87.6 86.7 87.3 85.3 32.5 36.0 35.9Mean refractometer purity 89.8 90.3 87.9 88.5 88.6 86.8 34.2 38.8 38.9-Composite samples.

-87-one calculated from the pol reading and densimetricBrix. For simplification, the former valueis henceforth called refractometer sucrose andthe latter dcnsimetric sucrose. Both of theseeffects result in refractometer purities beinghigher than densimetric purities.The differences between refractometer anddensimetric Brixes are far from being constant.They vary with the nature of the product andalso from sample to sample of the same sugarproduct according to the nature and amountof inorganic impurities and the amount ofsuspended matter present in the sample. Thelatter, in particular, affects the hydrometer to amuch greater extent than the refractometer.For the analysis of molasses two methodswere used: the densimetric Brix was read froma I : 10 (wt/vol) solution and a sample of thisdilute solution was taken for the sucrosedetermination as is the general practice inMauritius. The refractometer Brix was obtainedfrom a 1 : 6 (wt/wt) solution which was alsoused for the determination of sucrose, thisbeing the practice followed in Hawaii. Thesucrose %molasses, therefore, was not calculatedfrom the same polarimeter readings and inmany cases refractometer sucrose in molasses islower than dcnsirnctric sucrose. At Factory C,however. over the span of four weeks the meanvalues obtained were very close being 34.85 fordensimetric sucrose % molasses and 34.87 forthe refractometer value. Corresponding figuresfor Factory B were 34.62 and 34.21 and forFactory A over only one week 31.20 and 30.37.Thus at both Factory A and Factory Bdensimetric sucrose % molasses was higherthan refractometer sucrose % molasses. Thiswould not have been possible if the sucrose %molasses had been calculated from the samepolarimetric readings since the refractometerBrix was always lower than the densimetric Brix.It is felt that these apparent abnormalities weredue to random analytical errors which evenedout at Factory C over four weeks but were stillnoticeable at Factories A and B.From the figures obtained, it was possibleto calculate the recoveries and profit and lossaccounts for each test period. The resultsobtained are given in Tables 41 and 42.Table 41.Comparison of Boiling House Performance figures (or densirnetric and refractometer controls.Tons TonsPeriod Tons Sucrose S.J.M. Recoverable Sucrose Boiling Boiling Housein Recovery Sucrose at in House EfficiencyMixed Juice 100% RH.E. Sugar made RecoveryFactory No. of Dens. Ref. Dens Ref. Dill'. Dens. Ref. Based on Dens. Ref. Dill'. Dens. Ref. Dill'.weeksTrueWI.stock takingA 977.390 978.149 93.1 93.7 0.6 909.950 915.814 890.997 91.2 91.1 -0.1 98.0 97.2-0.8B 2 2654.202 2656.341 92.3 92.4 0.1 2449.828 2454.459 2391.328 90.1 90.0-0.1 97.6 97.4-0.2C 4 6120.339 6124.906 90.9 90.9 0.0 5563.388 5567.540 5497.581 89.8 89.8 0.0 98.8 98.7-0.1Table 42.Comparison of Losses % Cane with densimetric and refractometer controls.Sucrose Sucrose Total Sucrose UndeterminedPeriod % Extraction Losses Losses in molasses Lossescane 0'-;; cane % cane % cane % caneFACTORY No. of Dens. Ref. Diff. Dens. Ref. Diff. Dens. Ref. Diff. Dens. Ref. Diff.weeksA 14.59 14.60 .01 12.71 1.88 1.89 .01 0.67 0.65 -0.02 0.35 0.38 0.Q3B 2 14.37 14.38 .01 12.31 2.06 2.07 .01 1.05 1.04 ---D.OI 0.25 0.27 0.02C 4 14.72 14.73 .01 12.51 2.22 2.23 .01 0.77 0.77 0.00 0.62 0.63 O.oI

-88-From the tables it is noticed that, since therefractometer sucrose % mixed juice is higherthan the corresponding densimetric value by0.01, there appears to be very slightly moresugar in the mixed juice of the refractometercontrol, and this results in a Boiling HouseRecovery figure lower by a maximum of 0.1.At Factories Band C, the refractometer S.l.M.recoveries were between 0.0 and 0.1 higher thanthe densimetrie values, this difference being dueto the fact that suspended solids in the mixedjuice affect the hydrometer to a much greater extentthan the refractometer. As a result of thisdifference in S. J. M. recovery and of the differencein B.H.R., the refractometer BoilingHouse Eff'iciencies were lower than the dcnsimetrievalues by 0.2 at Factory Band 0.1 atFactory C. Since it happens every now andthen that Boiling House Efficiencies higher than100% are obtained with densimetric control,the lower values obtained with refractometercontrol are more realistic.At Factory A, over the short period of oneweek, the difference in the SJ.M. recoverieswas much greater, namely 0.6. This largedifference was mainly due to the fact thatrefractometer sucrose % molasses was lowerthan the densimetric value. At the three factoriesthe amount of recoverable sugar at 100%RH.E. was slightly lower for the densimetricfigures since both refractometer sucrose o~mixed juice and refractometer SJ.M. recoverieswere higher than the corresponding densimctricvalues.Refractometer sucrose % cane being 0.01higher than the densi metric value, total losseswere consequently 0.0 I higher too. At FactoryC, the sucrose content of the molasses beingnearly equal for the two controls, sucrose lossesin molasses ~'l; cane were also equal for both.At the other two factories, that was not thecase, and differences of 0.01 and 0.02 respectivelywere obtained. Hence, a difference of0.03 in undetermined losses occurred at FactoryA, 0.02 at Factory B, and 0.01 at Factory C.The refractometer offers several advantagesover hydrometers, the most important of whichare:(a)(b)(c)(d)(c)it yields more accurate Brix values that liecloser to the dry substance than correspondinghydrometer values,it is simpler to use,it necessitates only a small sample,the Brix determination is carried out muchmore quickly than with the hydrometer.it is a robust apparatus of a long life span.In view of these advantages, it is recommendedthat as from next year all factoriesshould be equipped with precision refraetometers.In order to enable the staff to become familiarwith the range of values of Brixes and puritiesencountered with the refractometer, parallelcontrol with the refractometer and hydrometersshould be carried out during several weeksbefore the hydrometers arc discarded.This will moreover provide for each factorya set of data that should be useful for comparisonsof factory performance in years beforeand after the transition from densimetric Brixesto refractometer Brixes.REFERENCESLAMUSSF, J. P. (1960) Preliminary studies in the useof the refractometer for routine chemical control.Rep. SlIg. Ind. Res. [fist. Mauritius: 101 - 103.HANSSON, F. (1940) Bausch and Lamb precisionrefractometer. Huwuii. Sit.!!. Plant. Assoc. Evp,Sta. Sug, Tech. Dept. Activities Rep. 4.HAWAIIAN SUGAR TECHNOLOGISTS (1955)Official methods of the Hawaiian Sugar Technologistsfor Control of Cane Sugar Factories,Revised Edition.SOCIETE DES CHIMISTES ET DES TECHNICIENSDES INDUSTRIES AGRICOLES DE MAURICE.(1948) System of Chemical Control for CaneSugar Factories.

-89~(b). THE DETER!\II\TATlO\T OF RETE"lTlO"l I\T VACUUM FILTERSJ. D. de R. de SAINT ANTOINE & E. C. VIGNESJn 196I, seventeen out of twenty-threefactories were equipped with rotary vacuumfilters. Although these filters offer numerousadvantages over filter presses, yet their juicescannot be sent directly to the evaporator butmust be pumped back to the mixed juice.If the amount of mud solids going through withthe filtrate is excessive, these solids tend tobuild up in the clarifier, and as already pointedout (SAINT ANTOINE and LAMlJSSE, 1959) maylead to clarification difficulties which are sometimeswrongly attributed to juice refractoriness.The best way of judging the performance ofavacuum filter is to determine its retention daily,retention being the percentage of the total mudsolids present in the filter feed which is retainedin the cake.The percentage of mud solids in filter feedor cake may best be determined directly by theuse of a centrifuge. The method, as describedin the fourth edition of the Laboratory Manualfor Queensland Sugar Mills (1961), reads asfollows:«For a mud (filter feed) or filter cake, 100 g.of material are taken and washed on a 100mesh screen until no trace of mud is left in thebagacillo. The washings are made up to 2,000g.and, after effective stirring, a subsample ofabout 1,000 g. is poured off and weighed. Thesubsample is then centrifuged and the solidsare redispersed, centrifuged again, dried andweighed. For a filtrate, 100 g. are centrifugedand the solids are redispersed, centrifuged again,dried and weighed.»When mud solids are determined directlyretention is calculated as follows:mud solids Brixper cent filtratefiltrate feedRetention ~~ 100~ x----x 100mud solids Brixper cent filtratefilter feedThe Brix terms are introduced in the aboveequation to compensate for filtrate dilutionduring washing of the cake.Unfortunately, sugar factory laboratories inMauritius are not equipped with centrifuges.Consequently, sugar chemists must resort tosome indirect method for the determination ofmud solids and the calculation of retention.However, mud solids, when obtained indirectly,may be determined by different methods and theobject of the present study was to compare theretention values obtained by several of theseindirect methods with a view to deciding whichone, if any, is suitable for the industrial controlof filtration, under the conditions obtaining atpresent in the laboratories of the island.In all the methods described hereunder,retention was calculated from the bagacilloratios of feed and cake on the assumption thatall the bagacillo present in the feed is retainedin the cake. Then,mud solids in cakePer cent retentionbagacillo in feedThe methods used for the comparisonswere the following:Method No. 1.bagacillo 111 cake------- x 100mud solids in feedThis method, in which mud solids areobtained directly by filtration, was adopted asthe standard method for comparing the resultsobtained with the indirect methods.(a)Mud solidsFilter feed (50g) or cake (20 g) is weighedand washed over a 200 mesh sieve until thewater runs clear. All the washings, whichamount to 3 to 4 litres are collected, measured

and well mixed. A one-litre aliquot portion istaken, 2 to 4 g Celite filter aid arc added andstirred in, and the mixture filtered in a Buchnerfunnel through a tared filter paper. The latteris then washed well with distilled water and driedto constant weight in an oven at 105°C. Mudsolids per cent in the original amount of feedor cake is then calculated from the increase inweight of the filter paper after deduction ofthe amount of filter aid added.(b)FibreFilter feed (50 g) or cake (20 g) is weighedand washed over a tared 200 mesh sieve untilthe water runs clear. Excess water is drainedoff and the sieve and contents dried in an ovenat 105°C to constant weight. Fibre per cent IScalculated from the increase in weight.Method No. 2.In this method and in the following ones,mud solids are obtained from the relationMud solids % 0= dry substance %- fibre%- Brix %(a)Dry substanceCalculated by drying a weighed amount offeed or cake to constant weight at 105°C.(b)(c)FibreDetermined as in Method No. 1 above.BrixBrix of feed is calculated from the expressionBrix =Pty.Pol o,~ feedclarified juicewhere Pol % feed is obtained by the sameanalytical procedure as that currently used forthe determination of pol in cake, and purityPol % g clarified juiceclarified juice C~---------- x 100Brix (dens.)Brix = --------- x 100Pty. 60/40 mixture-90 -x 100Brix of cake is caleulated from the expressionwhere the 60/40 mixture is one contammg 60per cent of cloudy filtrate and 40 per cent ofclear filtrate. The purity of the mixture is givenby the relationship.Method No. 3.Pol %s 60/40 mixture---------- x 100Brix (dens.)This method is similar to Method No. 2above. but instead of assuming a 60/40 mixture,a certain amount of cake is placed in a pieceof calico cloth and juice expressed. The purityof the expressed juice is calculated from therelationshipPol % g expressed juieeBrix(dens.)x 100and the Brix of the cake obtained by dividingpol ~.~ cake by purity of expressed juice andmultiplying by 100.Method No. 4.This method is similar to Method No. 2exeept that the Brix of feed and eake, instead ofbeing obtained by calculation, arc measureddirectly with the help of a refractometer. Forthis purpose a little feed is filtered throughcotton wool whilst a few millilitres of juice areexpressed from the cake with the help of apiece of calico cloth.Method No. 5.The only difference between this methodand No. 2 lies in the Brix calculation of thefeed and cake. Instead of determining thepurity of a 60/40 mixture, feed is strained in acalico cloth and the pol and densimetric Brixof the filtrate are measured.Then,Pol ~.~ g. filtratePurity of juice in feed =- x 100Brix (dens.)Pol % cake Pol % feedand Brix of feed-------- x 100Pty, juice in feed

-91-The Brix of the cake is obtained, as inMethod No. 3 by dividing pol % cake bypurity of expressed juice and multiplying by lOO.A number of retention figures were calculatedby each of the above methods and theresults obtained are given in Table 43.Table 43. Comparison of retention figures determined by different methods.Run No.MethodNo. IMethodNo. 2MethodNo. 3MethodNo. 4MethodNo. 5I23456789101112Av. runs 1-12Av. runs 6 - 12445965887574798067817560707458657194637477866882806674765362669260737482647874637073696967967010187lOO76III847183907580897193826980Of the four indirect methods used for thedetermination of retention in vacuum filters,Methods 4 and 5 yield inflated values.Methods 2 and 3, the latter in particular,give results which are, on the average, in closeagreement with the mean value found byMethod 1. It should however be stressed thatindividual retention values, when obtained indirectly,cannot be very reliable as they areaffected by too many sources of error. But ifretention is calculated twice daily, and theaverage of the twelve results obtained for theweek is worked out, the factory chemist willbe in a position to evaluate the efficiency offiltration from week to week.As already pointed out. the best method toutilize for the determination of mud solidsand the calculation of retention in vacuumfilters is that in which the mud solids are centrifuged,dried and weighed. Centrifugation isto be preferred to filtration, as employed inMethod I, which is delicate, tedious and timeconsuming and cannot consequently be usedfor the industrial control of filtration.In conclusion, it is recommended thatMethod 3 be adopted in all the sugar factorylaboratories of the island for the calculation ofretention. Two determinations should becarried out daily and the average value workedout for the week. This recommendation,however, is only temporary and will no longerbe valid as soon as sugar chemists have centrifugesat their disposal. They will then be ina position to determine mud solids directly andmore accurately.REFERENCESANON. (1954) The operation of rotary vacuum filters.Tech. Rep. 17, Sugar Res. Inst. Mackay.Laboratory Manual for Queensland Sugar Mills.3rd. ed. 1954, Brisbane, 104. 135-136.Laboratory Manual for Queensland Sugar Mills.4th ed. 1961, Brisbane, Ill, 146.

-92-6. QUALITY DETERMINATION OF CANE IN THE FACTORYJ. D. de R. de SAINT ANTOlNEIt is oftcn necessary to obtain informationon the quality of cane grown on the varioussections of sugar estates, For instance, when avariety is released for commercial production,its yield of sugar per arpent should be calculatedfor thc different sections of every estate whereit is grown and the results compared with thoseof the standard varieties grown.Several methods are available for the determinationof cane quality. A reliable one isthe so-called «long test» which is an indirectmcthod and in which the weights of cane,mixed juice and imbibition water are carefullynoted and the sucrose and fibre per cent canevalues calculated with the help of analyticalfigures. The long test is not practical, however,as it necessitates large tonnages of cane equavalentto about one hour of crushing time,Direct methods of analysis, such as theCane Chipper - Rictz Disintegrator methodadopted at this Institute, must therefore beresorted to. The latter method, however,cannot bc used at present in sugar factorylaboratories, through lack ofequipment. Further,whereas sampling of cane stalks from the latinsquares of small experimental plots can befairly representative, it would be extremelydifficult to obtain a representative sample ofsome thirty canes only, say, from a commercialfield of several arpents. Hence it would be amuch better proposition to sample thc knifcdor shredded cane, throughout thc crushing ofthe consignment to be tested, and to an" lysea sub-sample directly for sucrose and fibre.This direct analysis, however, calls for a largeand robust disintcgrator which is often notavailable and which suffers from two majordisadvantages:(a)(b)The long duration of the disintegrationperiod which amounts to about 45minutes (HARRIS et al., 1959).The difficulty in obtaining an accuratejuice purity figure, because of the largevolume of water and consequent juicedilution that must be used for thedisintegration.It is true that juice dilution will not affectthe sucrose and fibre calculations and that themain criteria governing the choice of a canevariety are its yield and its sucrose content.Yet a better assessment of the variety is madewhen juice purity is determined concurrentlysince sugar recovery in the factory is greatlyinfluenced by the amounts of soluble nonsugarspresent in the cane.When a sample of even a few tons of caneis crushed in a factory, it is an easy matterto obtain a representative juice sample Shouldit be possible to correlate the analysis of 1stexpressed juice, say, with sucrose per cent cane,it would thcn be easy to assess the quality ofvarious cane consignments. As a matter offact, thc ratio Pol :;,; gIst expressed juice tosucrose % cane, or so-called Java Ratio, isused in South Africa to assess the quality ofplantcr..' cane.Tile Java Ratio method of determiningsucrose per cent cane has the big advantage ofbeing simple and of using a product, 1stexpressed juice, which can be easily and represcntativclys.unplcd. Unfortunately it suffers fromthe major drawback that it does not take intoconsideration the fibre content and cannottherefore determine accurately the sucrosecontents of canes hav ing different fibre percentages.Should it be possible to correct the JavaRatio for fibre, the accuracy of the assessmentof cane quality would be greatly enhanced andwould no doubt meet the needs of agronomicrequirements at least. A step in this directionis made by those chemists who use the CentralBoard's method of calculation of the sucrosecontent of planters' canes for assessing thequality of the cane varieties grown on thevarious sections of estates. In this method,which has been fully described elsewhere

-93-(SAINT ANTOINE, 1959) the 1st expressed (or 1stmill) juice is analysed for Brix and Pol whilstfibre % cane is determined with the help of aCutex fibrator on a sarnplc of 30 canes pickedat random from the cane carrier during the test.Purity of absolute juice is obtained by deductingfrom that of 1st expressed (or 1st mill)juice the difference that exists between theabsolute and 1st expressed juice (or 1st milljuice) purities of all the canes crushed by themills during the week. Brix of the absolutejuice is calculated by the arbitrary relationshipand an arbitrary sucrose content of the caneunder test calculated with the help of theformula.Sucrose % cane =10,000Brix of absolute juicePurityFibre ~~ caneThe same calculation may be used for allthe canes crushed by the factory during theweek and an arbitrary sucrose per cent valuealso figured out for those canes. The differencebetween the two arbitrary values is then appliedto the actual sucrose per cent of all the canescrushed during the week as given by the weeklybulletin of the laboratory. This step, however,is often omitted as it only serves to bring thefigures to a more realistic value, but does notaffect the differences in sucrose contents measured.Whereas the above method, with furtherrefinements such as the calculation of fibre andsucrose balances, suits the purpose of theCentral Board, it cannot be recommended forthe assessment of the relative quality of canesgrown on different sections of estates for thefollowing reasons:(a) It is not correct to assume that thesame relationship between BA and BIholds for all the canes tested. It wouldbe more logical to use the relationshipBA/B l actually obtaining for all the(b)canes crushed during the week, but itwould still not be possible to usedifferent ratios in different tests.Similarly, it is incorrect to assume thesame difference between PI and PAfor all the tests carried out duringone week.(e) The influence of fibre on sucrose %cane in the so called Central Boardmethod is governed solely by thefactor (lOO ~ F). In the methodproposed hereunder the relationshipbetween Java Ratio and fibre isderived from practical results only,and thus any other factor involvedis automatically taken into account inthe calculation of sucrose % cane.(d) Thirty canes picked at random fromthe cane carrier cannot yield a representativesample for the determinationof fibre.(e) As already demonstrated (SAINT ANTOlNEand LE GUEN, 1960) it is not possibleto obtain reliable fibre values whenusing the Cutex fibrator.In view of these important sources oferror. it is recommended that the followingmethod which is based essentially on practicalresults and which makes use of a Java Ratiocorrected for fibre, be adopted instead.If the weekly Java Ratios obtaining in afactory for all the canes crushed is plotted asa function of corresponding fibre per cent canevalues, a straight line relationship is obtained, asshown in fig. 29. The figures used for drawingthis graph were obtained at Mon Tresorfactory during the 1961 erop and are given inTable 44. The equation of the straight linehas been worked out and reads as follows:J.R. = 103.26 - 1.66 F %CNow, if this equation is used to calculateweekly Java Ratios and hence sucrose per centcane. it will be seen, as shown in Table 44,that the calculated sucrose per cent cane valueslie very close to the true values. Thus in thecase of Mon Tresor maximum deviations were-0.17 to -,- 0.20, the correlation coefficientbeing 0.88 (significant at 0.1 per cent level).

-94-Table 44.Mon Tresor sugar factory 1961 crop, actual and calculated analytical figures.Pol. % g Sucrose Fibre Java Java Sucrose DifferenceWcek 1st Exp. %cane %cane Ratio Ratio %cane in sucroseNo. juice actual actual calculated calculated % cane13.11 11.06 11.95 84.4 83.42 10.94 0.122 13.21 11.02 12.71 83.4 82.16 10.85 0.173 13.69 11.21 12.54 81.9 82.44 11.29 -0.084 14.00 11.63 12.17 83.1 83.06 11.63 0.005 14.20 11.76 12.20 82.8 83.01 11.79 -0.Q36 14.27 12.02 11.78 84.2 83.71 11.94 0.087 14.91 12.39 11.77 83.1 83.72 12.48 -0.098 14.96 12.43 12.77 83.1 82.06 12.28 0.159 15.49 12.68 12.15 81.9 83.09 12.87 --D. 1910 15.88 13.16 12.60 82.9 82.34 13.07 0.0911 16.39 13.52 12.23 82.5 82.96 13.60 --D.0812 16.89 13.94 12.32 82.5 82.87 13.99 --D.0513 17.10 13.94 12.81 81.5 82.00 14.02 --D.0814 17.35 14.05 13.32 81.0 81.15 14.08 -0.0315 17.47 14.11 13.59 80.8 80.70 14.10 0.Ql16 17.76 14.17 13.55 79.8 80.77 14.34 -0.1717 18.Q7 14.45 13.80 80.0 80.35 14.52 --D.0718 18.20 14.62 13.78 80.3 80.39 14.63 --D.0119 18.80 15.02 13.90 79.9 80.19 15.Q7 --D.0520 17.89 14.59 13.40 81.6 81.02 14.49 0.1021 18.29 14.46 14.11 79.1 79.84 14.60 --D. 1422 16.61 13.48 14.04 81.2 79.95 13.28 0.20

o..8584,.80"j::I BR E~i~c xn s-95 ---e 82a:"> 8 I".,Fig. 29. Java Ratio as a function of fibre in caneMan Tresor, 1961 crop.Graphs have also been drawn, figs. 30 and31, and equations worked out for two otherfactories, Mon Desert and Union Flacq, forthe 1961 crop. The relationships found are:o...3" 8'a:-e> 8."Mon Desert : J.R. = 99.43 -- 1.56 F %CUnion Flacq : .T.R. = 91.56 - 0.82 F %CThe maximum deviations obtained in calculatedvis true sucrose arc respectively -D.26 to +0.13and -0.15 to + 0.13, and the correlation ccefficientsbeing 0.93 and 0.89 (both significant at0.1 per cent level).18 +----~r-----_,----_._---__,IQ I1 1213Fl eRE /0 CANEFig. 30. Java ratio as a function of fibre in cane,Man Desert, 1961 crop.It is recommended that the method outlinedabove be adopted in future by factory chemistsfor the assessment of cane consignments fromvarious sections of estates. Since the result, of83the tests arc gencral1y not needed by theManager before the cnd of the crop, it is Letterto wait till that time before plotting the graphand calculating the relationship for a particularyear and a particular factory. Should it howeverbe necessary to obtain results earlier in the,.80crop, it would still be possible after. say, eightweeks crushing, to calculate a provisional relationshipfor the purpose.An important point to stress, however, is18 +-------r----r-----,-----__, the sampling and analysis of cane for fibre. For11131415 agronomic purposes, it is a much better propositionto sample the cane in the fields thanon the cane carrier. Five contiguous canesshould be picked at random from at least sixdifferent spots in the field, sub-sampled IIIthirds in the usual manner, and taken to thelaboratory for analysis. If a robust disintegratoris available, however, it would be more accurateto sample the cane after the knives orshredder throughout the duration of the test andto use a sub-sample for the fibre determination,in spite of the disadvantage that completedisintegration would take about 45 minutes,as already pointed out.In the absence of a heavy disintegrator, theChemist would have to resort to the CaneChipper-Rietz Disintegrator method, whichyields accurate and consistent results. Theequipment is unfortunately not available as yetin sugar factory laboratories. Until such time as,,-0"..·• e a·>~ 8 I'079-l----,---~-----r---.....,...---,'011 12FIBRe: % CAN!Fig. 31. Java ratio as a function of fibre in cane,Union Flacq, 1961 crop.""

-96 --it is, or a heavy disintegrator is at hand, the onlyalternative is to use the Cutcx fibrator, althoughit has already been shown that fibre per ccntcane cannot be determined accurately with thehelp of this machine. However, the influenceof fibre on the calculation of sucrose per centcane by the proposed method is not excessivelylarge. If, for instance, actual fibre is 12.0 percent, an error of one unit in fibre wouldaffect the calculated sucrose per cent value asshown in Table 45 for each of thc three casesstudied. A value of 16.0 is assumed throughoutfor pol. /~ g. 1st expressed juice.Thus an error of one unit in fibre resultsin a discrepancy of 0.14 to 0.27 in sucrose percent cane. These values are possibly not excessivelyhigh for agronomic purposes, but sinceerrors of more than one fibre unit are oftenencountered when the Cutex fibrator is used,it is strongly recommended that a more accuratemethod bc adopted for the determination offibre in cane.Table 45. Influence of accuracy of fibre determinationon calculated sucrose per cent caneFactory Fibre %cane Sucrose % cane11.0 13.60Mon Tresor 12.0 13.3313.0 13.0711.0 13.16Mon Desert 12.0 12.9113.0 12.6611.0 13.21Union Flacq 12.0 13.0713.0 12.94REFERENCESHARRIS, S. R. et al. (1959). Direct analysis of canein Mauritius. Proc. lnt, Soc. Sugar Cane Tech.using a wet disintegrator. Proc, Int, Soc. SugarCane Tech., 10: 188-99.10: 163-67.SAINT ANTOINE, J. D. de R. (1959). Cane PaymentSAINT ANTOINE. J. D. de R. and LE GUEN, F. (1960).Cane Analysis. Mtius Sug. lnd. Res. Inst, PrivateCirculation Rep. 15.

BY-PRODUCTS1. THE COMPOSITION OF SCUMS AND HEAT COAGULATES FROM CANE JUICEIN RELATION TO THEIR NUTRITIVE VALUE TO ANIMALSD. H. PARISHSEED proteins form the basic food proteinsource of the Mauritian population, andeven these low biological value proteinsare consumed at such low levels that dietaryprotein deficiency is extremely common. Theproteins of high biological value. meat,milk, fish and eggs are expensive and moreovera large part of them are imported.It is essential. therefore. that any localsource of protein shall be exploited to the full.particularly as a rapid increase in population istaking place without concurrent increase innational wealth.This problem of protein shortage is notpeculiar to Mauritius, however. the carbohydrates,starch and sugar, are in plentiful supply asextremely high yielding crops producing thesematerials are widely grown, whilst fats, thealternative source of metabolic energy can befed without any ill effect over a wide range oflevels depending on their availability. Dietspoor in vitamins can be supplemented withsmall quantities of high vitamin food or withthe now cheap artificially produced materials.and mineral supplementation of any diet ischeap and simple. Protein. however. remains thecentre of dietary requirements; it must be fedat fairly high levels, its chemical constitutionmust be adequate for body needs and it cannotbe replaced by any other material.The elimination of protein as a limitingfactor can be made in two ways: increasedproduction of high quality protein and increasedefficiency in its utilization.Increased production is a slow and highlycapitalized procedure. particularly where malnutritionis already a problem. but increasedefficiency of utilization can be cheaply and simplyobtained.As has been pointed out, the normalvegetable sources of human dietary protein aregrains and pulses both of which contain lowvalue proteins. Tile next dietary sources are theanimal proteins synthesized basically from theproteins of plants. Leafy materials althoughthey contain protein of high biological valuecannot be used directly by human beings becauseof the high levels of fibre.The indirect utilization of plant proteinsthrough stock rearing is inefficient as shownby the data (Table 46) from LEITCH andGODDEN (1952).Table 46.Efficiency of domestic animals in the conversion of vegetable protein to animal's protein.Efficiency %Milk - whole life 18.1Beef - Baby (to 7 cwt) 15.3Fat bullock (12-15 cwt) 8.7Lamb 13.2Pork 19.0Poultry - table 21.0 - 26.0Medium light bird(1 egg daily) 39.7(200 eggs a year) 26.4

_ ll') -Beef production is seen to be tile mostwasteful way of converting vegetable proteinto animal protein, pork production is betterand egg production, particul.rrty with high layingstrains, the best; high yielding milch-covs a",fairly efficient protein converters but low yieldinganimals will not be. Apart from the highperformance laying hen, however, the efficiencyof conversion of vegetable protein to animalprotein is poor, being only about one sixth,If leaf protein is taken as being the dietaryequivalent of animal protein, then the wholesystem of converting leaf protein to human foodis extremely inefficient and PIRIE (1942), consciousof this inefficiency, has been the motivatingforce behind much of the work in progress onthe separation of leaf protein from fihre withthe final aim of preparing a material suitablefor direct human consumption, The preparationof a low fibre leaf protein for use in pig andparticularly in poultry rations would, however,be helpful in increasing the efficiency of leafprotein utilization and could be considered as afirst step.The only crop of importance in Mauritiusis sugar cane and although the green topscould be used as a source of protein, [PIRIE(l960b)] the dietary utilization of the proteinin cane juice has been neglected.BONAME (1897) stressed the value of SCUl11Sas a potential fodder and pointed out that theywere used in the West Indics as food for oxenand pigs, whilst PRINSEN GEERlIGS (1921) speaksof the use of filter press cake as food foranimals and mentions that it was even eatenby the poor of the district.Interest in seUl11S or juice as a source ofprotein evidently declined as WIGGINS (1960),in a review of the sugar cane crop as a sourceof materials other than sugar, passes over theprotein from the juice which is separated Inthe filter press mud as being unlikely to be ofcommercial interest.PARISH (1960), however, drew attention tothe fact that in Mauritius around 6,000 tons ofplant protein were being dumped in fields inthe form of filter cake in an island whosepopulation arc chronically short of dietaryprotein.This paper has led to attempts to preparea hig!] protein meal by centrifuging heated canejuice [Sr. i\:HOI:-

-99-impossible to obtain a reliable figure for lipidsand fibre using direct methods analysis, Thenormal petrol ether extract gives low resultsand apparently no method of extraction isfully reliable with material which has beendried at a high temperature [PIRIE (1961 lJ andas both SCU111S and the coagulate contain veryfine particles of fibre the usual digestionmethods for determining fibre or cellulosearc not suitable,The fibre figure obtained by the indireetmethod used will be higher than the true fibrecontent as it will include some pcctatcs and othernon structural polysaccharidcs. whilst thefigures for crude fibre and sieved fibre will below due to the finely divided nature of thebagacillo.The NORMAN (1935) fibre which is In factobtained by the pre-treatment used in thedetermination of lignin is probably the bestindication of indigestible structural constituents,DISCUSSIONThe nutriuve value of filter cake will bediscussed in terms of its content of nitrogen,fibre, ash and lipids, in that order, and finallythe value of" the heat coagulate from cane juicewill be compared with scums and the value andpotentialities of these two materials assessedso far as is possible.It should be noted that scums and heatcoagulate will be almost devoid of the watersoluble B vitamins, and therefore diets forpoultry and pigs containing these materials willhave to be reinforced by high vitamin foods orvitamin supplements.Nitrogen.As the nitrogen in filter cake is principallydue to the protein precipitated fromjuice by heat and lime, then it is reasonableto speak of a crude protein (N x 6,25) content.Table 47 which gives the level of nitrogenand erude protein occurring in dried filter mudsfrom various countries shows that the materialfrom Mauritius is higher in crude protein thanthat from any other country. The Puerto Ricanfilter rnuds at their best reach the same levelof nitrogen as the best local samples but theiraverage content is lower.The average content of around seventeenper cent crude protein for Mauritius filter mudmakes this material, so far as protein is concerned,very attractive. it being the equivalentof a good quality dried grass. Sueh a level ofcrude protein is high enough for most produetionrations and more than enough for maintcnance rations.Dried filter mud containing only 11 %crude protein is of little nutritive interest toanimals other than ruminants. Material richerin protein becomes progressively more interestingas food for pigs and poultry as the proteinlevels increase and the material from filterpresses containing up to 20% protein is toogood a feeding stuff to dump in the fields.For ruminants, the amino-acid compositionof the protein is of no great importance but ifthe material is to be fed to pigs and poultry thenany amino-acid imbalance is a serious fault.Determination of the amino-acid compositionof filter muds and the heat coagulatehas presented some difficulty, although theresults so far obtained show the proteins to betypical plant proteins [PARISH AND FlGoN. (1961)]DUCKWoR1H AND WooDHAM (1961) andDUCKWORTH. HEPBURN AND WooDHAM (1961)have shown that leaf protein concentrates fedto chicks and rats compare with soya-beanmeal as a dietary protein source and when fedto newly weaned pigs were the equivalent ofwhite fish meal. This confirms the opinionsof PlRIE and others that leaf protein could beused as a substitute for animal protein inhuman diets. So far as cane juice protein isconcerned, however. the Icvels of the amino-acidsmethionine, lysine, and tryptophane will have tobe accurately assessed before the protein ofscums or coagulates can be taken as fully theequivalent of leaf protein.

-100-Table 47.Average N content %D.M. & crude protein content of filter cakefrom various countries.CountryAverageN % D.M.AverageCrude ProteinN x 6.25Range ofcrude proteinLouisiana .S. Africa .JavaArgentina ...CubaPuerto RicoMauritiusRotary FilterFilter Press!.I51.251.72.02.02.192.72.87.27.810.612.512.513.716.917.54.4 - 9.66.7 - 19.712.8 - 19.9011.4 ~ 19.30Table 48.The composition of the heat coagulate from cane juice and scums from six factories(average sample for last 6 weeks of crushing season 1961).CONSTITUENTCOAGULATES CUM S% Dry MatterRotary FilterFilter Press2 3 4 2Total Ash 8.9 14.7 9.0 12.7 14.3 11.0 13.7s.o, 5.5 4.3 3.0 3.2 4.3 2.9 3.0CaO 0.2 3.5 1.8 3.0 3.1 2.5 3.9PzOs 0.8 1.4 !.I 2.5 2.8 1.8 1.9MgO 0.2 0.3 0.7 0.7 0.5 0.6Crude Protein 23.0 12.1 11.9 13.2 14.0 15.7 15.3Total Sugars 16.1 12.1 7.1 5.9 4.9 20.8 2!.IE. F. M. 24.9 43.4 34.0Benzene Extract (Hot) 25.0 9.4 13.5Crude Fibre 17.3 11.3Fibre retained on 100 mesh sieve Nil 14.8 14.3 9.6Norman Fibre 13.7 25.9 21.5

-101--Fibre and insoluble carbohydrate.As has already been pointed out, it isdifficult to obtain an accurate quantitativefigure for the level of fibre in filter cake.By using extracti.ve free material an approximatefigure for insoluble carbohydrate has beenobtained but this figure probably includesmaterials which are digestible and could betherefore used as a source of energy.The crude fibre figures indicate a level ofabout 17% for rotary filter cake and II % forfilter press cake whilst the material retained ona 100 mesh screen is about 15% and 10%respectively.The crude fibre figure as an indication ofdietary bulk is certainly low, whilst the insolublecarbohydrate is too high a figure.More work will have to be done on thecomposition of scums before a proper fibrefigure can be given but the result so farobtained shows that the ratio of bulk ofrotary filter cake to filter press cake is around3 : 2, and that so far as animals lacking a gutspecially adapted for fibre digestion arc concerned,the indigesti bIe structural matter ispossibly in the range of 20 to 30 % dependingprincipally on the type of filter used.Ash.The principal constituentsfraction are the nutritionallysilica and the essential nutrients,phosphorus.of the ashunimportantcalcium andThe recommended dietary levels of calciumand phosphorus for cattle are around 0.3 % Caand 0.25% P [MAYNARD and Loost.r (1956)]which is much lower than the level of thesematerials occurring in filter cake.The ratio of calcium to phosphate in dietsis also of interest and it is generally recommendedthat the ratio should not exceed thelimits 2: I to I : 2: however, with adequatesupplies of vitamin D, ratios considerably widerthan this can certainly bc fed.From Table 48 it is seen that the averageration of Ca: P for filter cake is 2.7:1 but thecalcium and phosphorus levels of scums varyvery widely and in fact for the few samplesanalysed the Ca: P ratio varies from over 4: I to1.8: I.A high Ca and P content is not reallyimportant from the nutritional point of view asmineral supplementation with calcium phosphatesand limestone is cheap. But, nevertheless,for laying hens in particular, thc calciumand phosphorus content of scums is a usefulmineral supplement.Lipids.The lipids of filter cake have been fairlyintensively studied because of the interest inproducing a commercial sugar cane wax fromthis source.The level of lipids actually occurring infilter cake is difficult to determine as, particularlywith material dried at high temperatures,fixation of lipid by the protein apparentlyoccurs [PIRIE (1961)], but a level of around 15%seems to be the average.The lipids vary from the nutritionallyinert hard wax to soft oils containing palmitic,oleic and linoleic acids, and apparently, importantquantities of sterols also occur.Normally, digestible fat is equated as theenergy equivalent of digestible carbohydratex 2.3 but it would seem that fairly intensivestudies on the lipids will have to be madebefore such a factor could be applied to thedigestible lipids of filter cake, A high waxcontent is not a desirable feature as it is generallyaccepted that this can depress the digestibilityof a ration, presumably by protectingfood particles from cnzyrnatic attack.In addition to the sterols, some of whichmay be physiologically active, or activable asanti-rachitic factors, the lipids of scums containsome carotene [BALCH (1947)], however not insufficient quantities to act as dietary supplementsof this vitamin A precursor.The nutritive value of filter cake.Apart from the small amount of sugar(20 % on filter press cake and 10% from rotaryfilter cake) and the unknown amount of digestiblcpolysaccharide, the other energy source isthe lipid fraction, which as has been pointedout, is probably of low value for this purpose.The energy value of filter cake will decideat what level the material can be fed to nonruminants.

···102The basic division of farm animals intoruminants and pigs and poultry separates thoseanimals which can deal with bulky rations fromthose which cannot. and at the same time itseparates the animals which can utilize poorquality protein, and in which the gut microflorasynthesize the requirements of B vitamins,from those which need good quality proteinand carefully balanced diets rich in watersoluble vitamins.From the analytical data presented in thispaper, it is clearly seen that ruminants couldbenefit from fairly high dietary levels of seumsboth as a source of protein and energy.Poultry, particularly laying hens, are efficicntconverters of dietary protein to animalprotein but they can handle only limitedquantities of fibre. With a protein of highbiological value fed at a level of 15%which is the requirement for a laying hen,scums would have to be fed at high levels toreplace most of the protein in the ration, andas the only source of energy is the digestibleoil and the smaJl quantity of sugar and digcstiblepolysaccharide, the energy supplied will befairly low and the bulk presumably high.Thc calcium and phosphate would beadequate but much vitamin and somc mineralsupplementation of the filter cake would haveto be made.Grass can supply up to 20 n,; of the rationof laying hens and presumably filter press cu kccould therefore supply up to 20"" of the r.ui.intoo; this would mean that about 1/'+ of theprotein requirements of the hen could be metby scums, which is a significant dietary contribution,as the protein of the filter cake is,presumably, of high biological valuc.Perhaps this level of 20~.:' replacement couldbe pushed higher, particularly if tile lipids showa high digestibility; however, only egg l.iyingtrials will give the correct answer.After the hen, the pig is the most profitableconverter of plant protein to flesh; again,however, the presumably low energy value ofscums and their fairly high fibre means thatonly low levels can be fed,The difference in fibre levels between filterpress cake and rotary filter cake means, asfibre is a limiting factor in the rations of pigsand poultry, that the Icvcl of consumption ofrotary filter cake could only be at about 2/3of thc level of filter press cake fed.For these reasons. it is the ruminant animalwhich will present the least problems m theextensive feeding of filter cakc.Molasses is acheap source of energy andmoreover would make the filter cake extremelypalatable. BROWN et al (1959) studied theeffect of feeding combinations of bagasse andmolasses ranging from 45 % bagasse T 25 %molasses to 20 % bagasse -I- 50 % molasses.The remaining 30 % of the ration was made upto supply protein, vit rrnins, minerals and additionalenergy.All the I ations were consumed and digestedwithout any kind of digestive disturbance, butthe most desirable level of bagasse was foundto be 20 o~ -i- 50 % molasses.Although these experiments showed that noadverse physiological effects occurred with anyof the rations tested, a reduction in ruminationwhen finely comminuted diets were fed has beennoted [TYLFR (1950»). DAYIS & KIRK (1958)found that bagasse pith was well digested byolder stock but state that it should not be fedto young animals,To feed up to 201:; bagasse would meanthat filter press scurns could be fed at morethan 50 % of the total rations and rotary filterscums lip to 40 ~{" but as for maximum efficiencyup to 501:; of molasses must be fed also,then properly balanced rations cannot be madeby feeding at these high levels.If the feeding of filter rnuds does not causephysiological defects such as preventing rumination,then a combination of molasses and scurnswhich could be fed at high levels is certainlypossible.The low level of vitamin A precursor wouldhave to be supplemented and it seems that apossibly ideul solution would be to mix choppedcane tops, scums and molasses and ensile,By a proper balancing of the constituents, anattractive cattle food could presumably be madecheaply and without inconvenience, The alternativeis to dry the filter muds and blend withmolasses to give a cattle-food which agauicould be fed at high levels,

-105-of research that could lead to a better utilizationof the protein contained in cane juice, andinvestigations were therefore initiated in 1960,both on the chemical and technological aspectsof the problem (PARISH, VIGNE:S and de FRO­DERVILLE).Cane juice contains very little protein, butas approximately five million tons are processedin the factories every crop, several thousandstons of crude protein could be recovered yearly.At present, most of the protein contained in thejuice finds its way into the filter cake which isreturned to the fields. Should it be possible touse this cake for the feeding of animals, itsprotein would be directly utilized and wouldreplace, in the rations, more expensive sourcesof this body-building chemical.A few references are found in sugar literatureon the direct utilization of filter cake byanimals. Thus BONAME, as far back as 1897,tried to encourage its use in feeding rations,whilst GEERLlGS mentions in the 1924 editionof his book Cane Sugar and its Manufacturethat filter-press cake is sometimes used asstock feed, or even as food for the poorerclasses of people.In spite of these claims, it would appearthat, for various reasons, filter cake has notsince been used to any large extent for nutritionpurposes. The main factors that must havegreatly limited its use are probably:(a)(b)(c)The highly ferrnentative nature of thecake which must be dried soon afterproduction so as to prevent deteriorationfrom setting in.The disorders that animals may sufferby the ingestion of certain chemicalsused for juice clarification.The protein content of the cake whichis lower than that of other concentratesand consequently necessitates the useof a bulky ration if the protein contentof the latter is to be replaced by caneprotein.(d) A somewhat high fibre percentageespeciallyin the cake from the vacuumfilters which arc used in 17 out of 23factories in Mauritius -- which maylimit the use of the product for thefeeding of non-ruminants.In August 1961, it was suggested by Mr.L. de Chazal. a member of tile Sugar IndustryResearch Institute Board, that filter cake, inspite of the above-mentioned disadvantages,might yet be useful in feeding rations. A fewmonths later, experiments were laid down at theResearch Institute, the results of which arc notyet available.The ideal solution would be the productionof a high protein, low bulk concentrate whichcould be used directly in pig and poultryrations - animals known to be efficient convertersof food energy - and which couldeventually be purified into a product suitable forhuman consumption. Should it be possible toextract juice protein in the form of a coagulate,the protein content of which would lie in theregion of 25 per cent. or better, that coagulatecould be used as the main source of proteinmaterial in the ration of animals without undulyincreasing the bulk of the ration.The value of a food protein dependsprimarily on its amino-acid composition and onits digestibility. PIRIE (1961) has shown thatleaf protein has the value suggested by itsamino-acid composition; it is better than mostof the seed proteins and as good as those offish.Preliminary experiments carried out in 1960at the Sugar Industry Research Institute haveshown that it is possible to extract crudeprotein from juice on a pilot plant scale, usinga Westphalia KG 10006 separator. The coagulateobtained was found to have, on theaverage, the following composition:Protein (N x 6.25)AshWax (benzene extract)Wax & fats (benzenealcohol extract)SugarsCellulose fibre (by difference)Per centdry matter15.714.514.921.012.036.8The amino-acid analyses of the hydrolisedprotein were also carried out and are publishedelsewhere [PARISH 1960, (b) ]. These analyseshave shown that the protein is a typical plant

-- 106 _.protein and could be well utilized as a foodstuffprovided that nothing injurious is presentin the material.As however, the protein content of thecoagulate was fairly low, amounting to onlysome 16 per cent., whereas its fibre and waxcontents were high, it was thought thatbefore the coagulate could be used as a feedingstuff, its protein content would first haveto be raised and its fibre content lowered.Accordingly, pilot plant experiments werecarried out at Medine Sugar Factory in 1961,after several modifications had been broughtto the extraction process. The new procedureadopted was as follows: mixed juicefrom the mills, after passing through vibratingscreens, was further strained through a 130­mesh stationary monel wire screen and colleetedin a tank fitted with a perforated steam coil.The juice was heated to about 90°C by steaminjection and fed by gravity to the Westphaliaseparator. The coagulated proteins were allowedto build up in the annular chambers of themachine under the action of centrifugal force.Centrifuging was continued until the clarifiedjuice ran cloudy, when the centrifuge bowlwas full. The machine was then dismantledand the cake removed and dried.It was thus possible during the crop toextract over one ton of coagulate which. onanalysis, revealed a marked improvementover that obtained the previous year as faras protein and fibre contents were concerned,as may be seen from the following figures :-Crude proteinAshWax (benzene extraet)Wax & fats (benzene alcoholextract)SugarsCellulose fibre (by difference)Per centdry matter22.89.025.039.616.112.5Thus, the coagulate extracted in 196I hada protein content of close to 23 per cent,whereas its fibre content was low. Further,this fibre was in a very fine state of division,having passed through a l30-mesh screen, andwas presumably easily digestible. It wastherefore believed that the coagulate, in spiteof its high wax content, could be advantageouslyused as a feeding stuff, and it was decided tocarry out preliminary feeding trials on milchcows. These feeding trials were conducted byMessrs. Serge Lionnet. Veterinary Surgeon, andClaude Delaitrc, Animal Husbandry Officer ofthe Department of Agriculture, and the followingnotes are taken from a report submittedby them.Milking cows were selected in preferenceto other domestic animals because of theirknown sensitivity to various influences. Further,milk production is a reflection of theutilization of the protein in the diet.Two similar lots of milking cows werechosen; two groups of seven Fresian crosseswere used at Benares S. E. and two groups ofCreole cows at the Government Farm inCurepipe. In each lot the animals chosenwere approximately at the same stage of lactationand producing roughly equivalent amountsof milk. Nearly equal weights of rations couldtherefore be fed to both groups.Two different rations were compounded,one was called "coagulate" and the other"control" and these terms are used throughoutthis paper. These rations were compoundedas follows :-Coagulate ControlMolasses 25.0 25.0Groundnut 12.0 12.0Cane juice coagulate 20.0Lucerne meal 20.0Cotton seed cake 13.0 13.0Bran 10.0 10.0Oats 5.0 5.0Maize 14.0 14.0Bone meal 0.5 0.5Salt 0.5 0.5100.0 100.0Both rations were supplemented, in thesame proportion, with adequate amounts oftrace minerals. The percentage of moisture,protein and fat in these rations were thefollowing :-

-104-REFERENCESABRAMS, J. T. (1961). Animo! Nutrition and VeterinarvDietetics. 'Iv\'. Green & Son, Edinburgh. .BALCH, T. R. (1947). Wax and Fatty Byproducts fromSugar Cane. Tech. Rep. Sug. Res, Fdn. N. Y.,3.BONAME, P. (1897). Ann. Rep. 510. agron. Mauritius,p. 68 -69.BROWN, P. B., RAMON, T. E., d'ESCRIVAIN, T. E.,SINGLETON, C. B., ROBERTSON, e. L. (1959).Sugar Cane Bagasse - Blackstrap MolassesRations with and without Hormones or Antibiotics.Sug. J., 22 (4): 13 - 19.DAVIS, G. K., KIRK, W.K. (1958). Bagasse as aCattle Feed. Sug . J. 21 (4): 13 - 19, 40.DUCKWORTH, r., WOODHAM, AA (1961). Leaf ProteinConcentrates. i. Effect of Source of RawMaterial and Method of Drying on Protein Valuefor Chicks & Rats. J. Sei. Food Agrie. 12 : 5 - 15.DUCKWORTH. s., HEPBURN, W.R., WOODHAM,A.A. (1961). Leaf Protein Concentrate. ii. TheValue of a Commercially Dried Product. forNewly Weaned Pigs. J. Sri. Food Agric. 12:16 -20.FElLLAFE, S.M. (I96/). Personal Communication.LEITCH, I., GODDEN, W. (1952). Teell. Connnun,Commonw. Bnr.Aniniat Nntr., 14. cited by:Chaycn, l. H., Smith, R. H., Tristram, G. R.,Thirkell, D., and Webb, T. - J. Sei. FoodAgric. 1961, 12: 503.MAYNARD, L.A., LOOSLl, J.K. (1959). Animal Nutrinon.4th Ed. McGraw - Hill Book Co. Inc.,London.NORMAN. A.G., (1935). The Composition of CrudeFibre. J. Agric Sci. 25: 529 - 540.OWEN, W.L. (1958). Fertilizing Value of CompostingFilter - Cake Muds. Sugar J. 12 (3) : 37 - 43.PARISH, D.H. (I 96Q). Protein from Sugar Cane.Nature, Lond. 188: 601.PARISH, D.H., FIGON, e. ([961). Sugar Cane as aSource of Animal Food. AIII/. Rep. S/!g. Ind.Res. Inst, Mauritius, 1960: 46 - 48.PIRIE, N.W. (19421. Direct Use of leaf Protein inHuman Nutrition. Cliem. & ltnl, 61 : 45.PIRIE, N.W. (l952!. Large-scale Production of EdibleProtein from Fresh LCH\/CS. Ann. Rep. RothamstedExp, Sto. p. 173.PIRIE, N.W. (1960). (a) AIIII. Rep. Rothamstrd Exp. SI".p. 109. (b) Private Communication.PIRIE, N.W. ([961) Private Communication.GEERLlGS, H.e. PRINSEN (1921). Cane Sugar and itsManufacture, Norman Rodgcr, London p, 182.SAINT ANTOlNE, J.D. de R. de, VIGNES, e. (1962).The Extraction of Cane Juice Protein and theAssessment of its value as a Feeding Stuff'. Rev.agrtc. suer. I1e Maurtce 41 (I): 25-30.SAMUELS, G., LANDRAU, P. (1956). Filter-Press cakeas a Fertili/cr. Proc. flit. Congr. Slig. Cane Tech.(India) 9: 119 - 131.STAUB, S.. DARNE, A. (1962). Rapport Preliminaire surI'Utilisaucn des Tourtcaux de Filtrcs-Prcssescorn me . Aliment pour les Anirnaux. Rev.agric. suer, lie Maurice 41 (I) : 31 - 34.DC TOlT, l.L. (1961. Filter Cake, Kraal Manure andCompost. S. Africa Sug. J. 45: 979 - 983.TYLER, e. (1950). Animal Nutrition, Chapman &Hall Ltd., London.VIGNES, r.c., de FROBERVILLE, R. (961). ProteinExtraction from Sugar Cane Juice. Anl/.Rep. Sug, Incl. RH. Iust., Mauritius 1960:93 - 97.WIGGINS, L.F. (1960). Sugar and its Industrial Applications.Royal Institute of Chemistry - Lectures,Monographs, Reports, 1960, no. 5.2. THE EXTRACTION OFCANEJUICEPROTEINANDTHEASSESSMENT OF ITSVALUEASAFEEDINGSTUFFJ. D. de R. de SAINT ANTOTNE & E. C. VJGNESIn many overpopulated, economicallyunder-developed countries, protein deficiencyposes one of the most acute nutrition problems.With the alarming yearly increase in populationin Mauritius and the island's limited sources ofrevenue, the prospects of an improvement in thesituation arc poor indeed. It is therefore imperativein our case to explore all the avenues

.- 103--Nutritive value of coagulate fromjuice.The composition of the heat-coagulate madefrom cane juice is given in Table 48.The protein level of 23 ~~ and the insolublecarbohydrate of 25 % give a low fibre to proteinratio: thus from the point of view of bulk, thecoagulate can be fed at up to twice the levelof rotary filter cake and will then supply aboutthree times the quantity of protein.For laying hem, therefore, there is a markedsuperiority of coagulate over scums when consideredin terms of protein and fibre.The coagulate is low in calcium andphosphorus but this is not a serious drawback;the level of lipids, however, is extremely highand analyses have indicated that one quarterof the material falls in this fraction. As itis not possible without further work to givean energy value to the lipid fraction, the valueof the crude coagulate cannot be accuratelyforecast but it is almost certain that the highlevels of wax will interfere with digestibility andso counteract any energy which may be availablefrom other lipids.No doubt the composition of the coagulatecan be improved by pre-centrifuging the coldjuice, which should remove most of the Iipids,thereby giving an improved protein content,which would make the material readily acceptablefor pig and poultry rations, and may evenlead to direct human utilization.CONCLUSIONSSTAUB AND DARNE (Ioc. cit.) aware of thehigher fibre levels in rotary filter seums than infilter press cake state that a change-over fromthe modern rotary filters to the old fashionedfilter presses should be considered.All scums arc fairly low in protein, whichis the main point of nutritional interest, andfairly high in fibre.The simplest use of scurns is as a directfeed for cattle for which low energy and largebulk are of little importance. This means thatboth types of filter mud can be fed, but theefficiency of utilization of the protein in termsof human interest is low.The value of scums as a fertilizer to thesugar industry taking a production of 25,000 tonsdried scums annually is around Rs. 2,000,000.If the industry were to revert to filter presses,the increased cost of production would haveto be added to the value of the seums;in any case, the ratio of fibre in filter presscake to fibre in rotary filter cake of 2 : 3 issufficiently close to make such a changeover ofdoubtful value nutritionally, let alone, economically.Estates are already carrying an annual lossof about Rs. 25/aere as a result of the removalof cane tops for cattle fodder and it is unlikelythat they would be prepared to subsidize thelivestock industry of this country by givingaway scums for feeding.The arguments put forward in this paper arebased mainly on analyses carried out in 1953,and the protein levels of filter muds occurringthen may not be exactly the same today.Detailed work on the composition andfeeding value of local filter cake will be carriedout during the 1962 crushing season, andresearch on the production of a high proteincoagulate from juice is to continue.The centrifugation of juice to prepare ahigh protein meal is expensive but the materialundoubtedly has more potential nutritionalinterest than filter cake; filter cake, however, isreadily available and is undoubtedly a valuablefood-stuff.In the end, economics will decide which isthe most suitable means of exploiting theprotein from cane juice but tilere is no doubtthat the interest now being taken in the feedingof protein from cane juice, either as coagulateor as seums, will lead to an improved livestockfoodstuff situation in Mauritius with concurrentbenefits to the whole island.

-107-MoistureProtein (N x 6.25)Fat (ether extract)Coagulate12.825.77.0Control13.424.43.4Both at Benares and at Curepipe, theanimals had been feeding on the same concentratemixtures for several months prior to thebcginning of the test. The milk production ofeach group was first recorded for a period of tendays while the cows were on their standardrations. The experimental rations wcre thenfed by gradual substitution over a period offour days.After seven days on the experimentalrations, the animals feeding on the coagulatewere given gradually increasing amounts of thecontrol rations, and vice versa, the change overtaking place in three days. After a furtherperiod of seven days, the two groups of eachlot were again gradually returned to their preexperimentalmixture, and milk records werekept for a subsequent period of ten days toenable the check ing of any possible after effects.Throughout the test, the animals at bothplaces were fed on the same lines, each animalreceiving 3/4 Ib of ration per kilo of milkproduced. Fodder was quite abundant and atBenares consisted of a mixture of cane topswith small amounts (one-fourth to one-fifth) ofSetaria grass, whereas at Curepipe it consistedof sugar cane tops only. The cows were providedwith fodder ad lib. and consumed dailyabout 70 kg each at Curepipe; at Benares eachcow received about 40 kg of fodder per day,the balance being made up by providing onepound of either coagulate or control mixturesdaily.The animals in each group were weighedprior to the test, and the total weights of eachbatch were fairly comparable, namely:Benares Group A 6131 lbsB 6092 "Curepipe Group A 5915 "B 6230 "The groups were reweighed after the testand it was observed that no appreciable changesin weight had taken place. Throughout thetest all the animals were regularly examined forgeneral condition and appearance, and noexternal changes were observed. Milk was alsoexamined regularly. and no unusual colouringor tainting was noticed.No difficulties were experienced as regardsfeeding; the rations were palatable and acccptcdat once by the individuals under test.Full rations were regularly eaten.The high wax content of the juice coagulatedoes not seem to have had any deleteriouseffect on the animals. An average sample ofdung excreted by one group of cows fed on thecoagulate showed a wax content of 3.9 percent, whereas a comparative sample from thecontrol cows of the same lot yielded 2.5 percent wax. It would thus appear that the waxycompounds in the coagulate are mostly inert.Graphic illustrations of average milkproduction per cow during the trial periods aregiven in Figs. 32 and 33. As may be observedfrom these graphs, milk production was notadversely affected by the replacement of all thelucerne meal of the ration. namely, 20 per centby weight. by juice coagulate. Although thecost of production of the latter has not yetbeen worked out, the separator used for experimentalpurposes being a small discontinuousmachine, there is no doubt that, should thecoagulate be produced continuously on anindustrial scale, its cost per unit of proteinwould be much lower than that of lucernemeal which has to be imported and sells atabout Rs. 325 per ton.Another interesting aspect of the resultobtained lies in the fact that it widens thescope of research in the field of nutrition.Whilst the value of the coagulate with regard tothe growth of young livestock is well worthtesting, it would also be necessary to try theproduct in rations compounded for otheranimals, in particular poultry and pigs. Unfortunately,most of the coagulate left overfrom that separated during the last sugar cropwas accidentally destroyed by fire so that withthe very limited quantity left, it will not bepossible to carry out more than one digestibilitytrial, on sheep. It is intended, however, toseparate more coagulate in 1962 in order tocarry out an extensive programme of experimentationboth on the intrinsic value of thecoagulate and in comparison with dry scums.

- 108 --zQRATION _;qIII1II"I_A_1III FIRST PER.IOO II 1II: II11I s 17 Iq 21EXPEfl,IMEN TAL[-B-:IIIIII2JnCOND PERIOD, I..... -1--........ __ ...---.........."',I \ I1 I vI II II II IIIIIIII 11 IIrI 1IBP£RIOO,I+- STANDARDIIIII1;J1RATlON---..'--'1Fig. 32. Effect of "coagulate" and "control" rations on average milk production per cow, Curepipe Dairy.GroupGroupABdotted lineplain lineDuring first period, Group A received "coagulate" and group B "control" rations, and viceversa during the second period.~~w~'":::; "zQ10u5~.."iCl ~w" C'" 8 wRAHON~:­1II14---A-----:F IRSl14---B--.jSECOND PERIOD :, , , ,,I> b10 12 Ib 18 20 22 2bC 26EXPERIMENTAL PERIOD D AY s..PERIODI11/III,,"r-__ .2 -- ... !.,10 H:STANDAf\OII,18 .0Fig. 33. Effect of "coagulate" and "control" rations on average milk production per cow, Benares S. E.GroupGroupABdotted lineplain lineDuring the first period, Group A received "coagulate" and group B "control" rations, andvice versa during the second period.

-109-ACKNOWLEDGMENTSExtraction of the juice coagulate was madepossible by the courtesy of the management ofMedine Sugar Estate Co. Ltd., and thanks aredue to the factory staff for their kind cooperation.The feeding trials were carried out atBenares Sugar Estate and at the GovernmentDairy in Curepipe, with the kind perrmssion ofthe Manager, Benares S. E. and the Directorof Agriculture, respectively.The authors also wish to acknowledge theassistance, in this project, of Messrs. SergeLionnet and Claude Delaitre who were responsiblefor the feeding trials.REFERENCESBONAME, P. (1897). Ann. Rep. Sta. Agron., Mauritius,p. 68-69.PARISH, D. (1960). (a) Protein from sugar cane.Nature, Land. 188: 601.PARISH, D. H., FIGON C. (1961). (b) Sugar cane as asource of animal food. Ann. Rep. Sug . Ind. Res.Inst. Mauritius, 1960: 46-48.PIRIE, N. W. (1961). More protein food from plants.Span,4 (\): 21 - 28.GEERLIGS, RC. PRINSEN (1921). Cane Sugar and itsmanufacture. Norman Rodger p, 182.VIGNES, S. C. & de FROBERVILLE, R. (1961). Proteinextraction from sugar cane juice. Ann. Rep. Sug.lnd. Res. Inst. Mauritius, 1960: 93 - 97.