the Symposium on Wheats for More Tropical Environments - cimmyt

317Lowlands withinadequate dry-season waterThis domain is comprised of bundedcropland, planted to flooded rice in <strong>the</strong>rainy season. but left idle in <strong>the</strong> dryseason because of insufficient or poorlymanaged dry-season water. Water forrainy-season flooded rice is mainly fromrainfall, with some also coming fromtraditional irrigation systems. Watercontrol (<strong>the</strong> ability to flood and drain atwill) is poor. because water movesdirectly from field to field, ra<strong>the</strong>r thanthrough subcanals. Wheat would haveto be grown, for <strong>the</strong> most part, withresidual moisture. Irrigation water. evenfor stand establishment, wouldcommonly not be available. Wheatwould not compete for land with o<strong>the</strong>rsecond crops, as none are generallygrown. However, <strong>the</strong> wheat-plantingseason conflicts with <strong>the</strong> rice-harvestperiod (late November to mid-January).This domain is characterized by heavyclay soils and covers approximately200,000 hectares or about 60% ofChiang Rai cropland.O<strong>the</strong>r domainsTwo o<strong>the</strong>r domains have been identified,but are assigned a lower priority. One issimilar to <strong>the</strong> lowland domain describedabove, but is fully irrigated in <strong>the</strong> dryseason. permitting farmers to plant asecond crop of flooded rice. The o<strong>the</strong>rdomain is also lowland. with relativelylight-textured soils on river floodplains.Farmers use this land with pumpirrigation in <strong>the</strong> cool season for highvaluecrops, such as tobacco and garlic.Wheat Production TechnologyWheat production technology for moretropical environments is not yet wellspecified. Numerous issues in cropimprovement and management remainunresolved (7). Consequently, <strong>the</strong>present assessment of <strong>the</strong> comparativeadvantage of wheat is preliminary. as is<strong>the</strong> specification of wheat productiontechnology itself.For <strong>the</strong> purposes of this study, "bestbet"wheat production practices wereidentified in cooperation with technicalscientists. Rainfed upland wheatproduction practices were specified as:• Land preparation by four-wheeltractor (two passes);• Manual planting in rows with a seedrate of 125 kg/ha of INIA66;• Fertilizer dosage of 30 kg/ha nitrogenand 38 kglha phosphorus, appliedbasally, and• Manual weeding and harvesting, andmechanized threshing.These practices result in a yield ofabout 1.000 kg of wheat per hectare.Lowland wheat production practicesand yields were specified as similar tothose described above, except that landpreparation is by rotortiller. A sharplyreduced labor input was also specifiedfor weeding; wheat after flooded ricefaces fewer weed problems than doeswheat after maize.If anything, <strong>the</strong> specified practices tendto consistently underestimate wheatproduction costs. For example,adequate land preparation for rainfedupland wheat after maize will likelyrequire more than two tractor passes;similarly, pre-irrigation and strawmulching may be needed for acceptablelowland wheat yields. These associatedcosts are ignored. More important, <strong>the</strong>specified lowland wheat technologyassumes that <strong>the</strong> conflict between riceharvest and wheat planting seasons canbe resolved at no fur<strong>the</strong>r costs to <strong>the</strong>farmer.Policies Affecting<strong>the</strong> Profitability of WheatProductionThailand's economic and agriculturalpolicies increasingly tend to favor freetrade (3). Most agricultural inputs are