the new jari - Philip M. Fearnside - Inpa

have a synergistic effect with iron toxicitycontributing to reduced absorptionof nutrients by the rice plant. Theplants respond to roots being puncturedby stink bugs by replacing them withadditional roots. Foliar symptoms ofnutrient deficiencies can easily lead tothe conclusion that increased fertilizerapplications are needed, a response thecurrent technical staff likens to treatinga human patient suffering from intestinalparasites by applying blood transfusionsor additional food. Increased attentionto insect problems may reduce the costand increase the effectiveness of futureresponses to these symptoms.Nematodes are an additionalproblem found by the currentteam of technical staff, which beganwork at the IRI Research Institute stationassociated with the rice project in thelatter part of 1980. The problem's severityand the possibility of control arestill under investigation. Aphids (Aphididae)in the rice roots and mites (Acari) ,are two additional problems discoveredby the present research team.Rice diseases presentinclude rice blast (Piricularia oryzae), towhich the IR-22 variety now being phasedout is very susceptible (but which didnot inflict economically significant lossesduring the time that IR-22 served as Jari'smainstay). Leaf scald (Rhynchoporiumoryzae) has been the most damagingdisease for both IR-22 and J-226. J-226seed is being propagated as a promisingreplacement for both IR-22 and the J-229progressively supplanting IR-22 since1979. Brown leaf spot (Helminthosporiumoryzae) is also present, as well as alittle false smut (Ustilagenoides virens).Although diseases represent a constantworry to rice growers, J ari's rice hasnot suffered unduly from them sofar. "Hoja blanca" virus, a majorproblem in Venezuela, has still notarrived at J ari. The most effective responseto disease problems is generallya switch to more resistant varieties, chemicaltreatments representing only a temporarymeasure. The greatest problemis ability to produce sufficient seed fastenough to effect a variety change whenand outbreak occurs (given that a resistantvariety is available in the pool ofstrains undergoing testing at the site).Sufficient seed was not available to completethe switch from IR-22 to J-229two years after the change began, andJ-229 is now already slated for replacementas soon as enough J-226 seed isavailable.Weeds are a continualworry in the Jari rice project, as in irrigatedrice everywhere. Barnyard grass(Echinochloa crusgalli) is present at low334levels throughout the rice area, althoughit has not exploded to inflict the severelosses it is capable of causing. Wild redrice (Oryza rufipogon) is now present atJari's Sao Raimundo rice project in lowlevels. Wild red rice is a major problemin many parts of the world because it isdifficult to distinguish from domesticrice (0. sativa), many seeds fall from thepanicles before harvest allowing it to reseedin the paddies, and any grainsharvested shatter when milled, thuslowering product quality. The most effectiveway to control these and mostother weeds is to pre-flood the fields togerminate the weeds, followed by drain.ing and multiple herbicide sprayings priorto flooding and planting. These timeconsumingand expensive procedures areso far only used for the seed productionbeds. In production fields weed control ispresently limited to one spraying beforeplanting (either Dalapon of Gramoxone),followed by spraying with Starn (Propanil)when the rice is growing. Onehigh spots. Another engineering changebegan in 1980: construction of an additionalcanal through the middle of eachlarge field, allowing independent fillingof each of the paddies into which thelarge fields are divided. The new canalsreduce the time required to fill a paddyfrom eight days to 36 hours. The newcanals in presently existing rice productionfields will be complete by the endof 1983, if the construction schedule isfollowed.Beginning in 1980, ricecrops are planted on a rolling basisrather than in two distinctly separateand more synchronized cropping periods.The number of crops obtained from anygiven paddy is still limited to two, asthe remaining time is insufficient for afull third crop. In the future the 1-226variety may allow about 30% of a fullcrop's yield to be harvested from resproutsas a stubble crop during this timeslot, but this possibility is still, in thetesting phase. Rotation crops other thanPolitical and bureaucratic decisions affecting the sylviculturaloperation may have at least as much impact on its ultimate sustainabilityas the many biological and agronomic threats to continued production.marantaceous weed (Thalia geniculata)has not been sucessfully controlled withthese procedures, but the problem hasnot grown to economically damagingproportions. Other weeds include an unidentifiedPhaseolus species, and anotherwild rice species (Oryza alta). Two majorgraminaceous weeds in Surinam ( Barett,nd. (1975) ) not yet arrived at Jari(R. Cheaney, personal communication,1980) are Leptochloa scabea and Jschaemumrugosum. The latter is consideredthe "most dangerous grass inSurinam" (Doeven and Peorink, 1955,cited by Grist, 197 5: 280) .A number of remediesare underway for the various agronomicproblems and the decline in rice yieldsmay not continue if these are effective.A major effort is improvement of thephysical structure of fields and dikes toallow more finely tuned and rapid responsesto water management problems.Fields are being regraded at considerableexpense. Slight depressions and "highspots" in the present fields have been aconstant headache hampering uniformflooding or drying of fields to controlinsects, weeds or other problems. Armyworms, for example, preferentially attackrice are also being tested, including sweetpotatoes (Ipomoea batatas), maize (Zeamays), sunflowers (Helianthus annus),sorghum (Sorghum vulgare), cow-peas(Vigna sinensis), winged beans (Psophocarpustetragonolobus), soya beans (Glycinemax), peanuts (Arachis hypogaea),and an unidentified local legume greenmanure crop. Taro (Colocasia esculenta)is being tested as a potential alcoholcrop, and a native papyrus (Cyperusspp.) may be tested as a potential pulpsource. Rotation crops could help reducepest problems, as well as fertilizer costsin the case of green manure crops.The search continuesfor rice varieties more tolerant of suboptimalmanagement, and for varietieswith greater tolerance for iron toxicity.Variety screening continues, as well asresearch on possible rice managementchanges. Research on annual crops onterra firme (unflooded uplands) at SaoRaimundo was discontinued in 1979.Better insect populationmonitoring methods have been institutedin the irrigated rice fields (sweep nettransects rather than 1 m2 quadrats),and spraying programs have been adaptedto try and control more insect out-NOV- DEC 1982, VOL. 7 NQ 6 IIVERlJENJR