the Symposium on Wheats for More Tropical Environments - cimmyt

262In pilot sowings in <strong>the</strong> Philippines. <strong>the</strong>average labor expenditure for handweeding has been about 25 man daysper hectare (12). although somefarmers' fields have required doublethis amount. Mechanical aids toweeding (rotary hand weeders. hingedhand hoes. bullock-drawn shallowplows and harrow weeders) are beingpromoted. However. a cheaper andmore satisfactory solution in <strong>the</strong> futuremight be chemical weed control.Some commercially aVailable herbicides(e.g.. Butachlor. Alachlor. Oxadiazonand Isoproturon) have been testedexperimentally with acceptable results(5.18.19). However. in practice. <strong>the</strong>rehave been phytotoxicity problems with<strong>the</strong>ir use. related to <strong>the</strong> level of soilmoisture following application and toseeding depth. Recently. a wider rangeof chemicals have been tested inThailand and in <strong>the</strong> Philippines. Theseexperiments have consistentlydemonstrated that a Diclofop-methyland Chlorsulfuron mixture adequatelycontrols weeds. including volunteerrice.Fertilizer TechnologyYield responses to nitrogen have beenobtained from applications of up to 40kg of nitrogen per ha in rainfed upland(14) and lowland conditions (S.P. Liboon.personal communication). and 80 to 120kglha with irrigation (15. S.P. Liboon.personal communication). In noexperiment has split nitrogenapplication demonstrated a clear yieldadvantage over totally basal application(5. S.P. Liboon and O. Werasopon.personal communication). Phosphoruslevels measured in many soils in <strong>the</strong>region are low (often less than 5 ppm.using <strong>the</strong> Bray II method). It issurprising. <strong>the</strong>n. that virtually noresponse to phospa<strong>the</strong> fertilizers hasbeen obtained, even at rates up to300 kg of P205 per hatThere have been no responses topotassium. and little experimentation ono<strong>the</strong>r elements. However. <strong>the</strong> generallylow yields obtained with adequatemo~ture. nitrogen. phosphorus andpotassium. <strong>the</strong> response to organicmanure in nor<strong>the</strong>rn Thailand (17) and astudy of micronutrient deficiencesltoxicities in Asian paddy soils (7)indicate this to be a potentiallyproductive area of study.References1. Abon. C. 1984. Wheat pilot projectin Nueva Ecija. Report of <strong>the</strong>Research and Development Center.CLSU. Munoz. Nueva Ecija.Philippines.2. Anonymous. 1983. The nationalcoordinated wheat pilot project.Progress Report. PCARRD.Philippines.3. Anukularmphai. A.. M.Shabiruzzaman and M. EnayetUllah. 1980. Rainfall andevaporation analyses of Thailand.Division of Agricultural and FoodEngineering. The Asian Institute ofTechnology. Bangkok. Thailand.4. Benoit. G.R.. and D. Kirkham.1963. The effect of soil surfaceconditions on evaporation of soilwater. Soil Science Society ofAmerica Journal 27:495-498..5. Campos. F.• R. Tabien. R. Camachoand C. Aganon. 1982. Syn<strong>the</strong>sis ofresearch results on wheat at CLSU.Report of <strong>the</strong> Wheat Research andDevelopment Program. CLSU.Munoz. Nueva Ecija. Philippines.