Annual Report 1961 - BEEP

-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-