the Symposium on Wheats for More Tropical Environments - cimmyt

237applied without increasing <strong>the</strong> risk ofyield reductions (Figure 7). Thus.production costs can be lowered (5).Adverse environmental factorsassociated with improper soilmanagement and diseases areconstraints affecting wheat productionin <strong>the</strong> Brazilian semitropical areas.Considering <strong>the</strong> high cost of productionand <strong>the</strong> high value of land in <strong>the</strong>seareas. appropriate technologies must begenerated and adopted. especially interms of land use and soil management.in order to minimize environmentalconstraints. increase wheat productionand lower production costs.Agricultural scientists are challenged todevelop efficient alternative soilmanagement and cropping practices.appropriate to <strong>the</strong> environment and tofarmers' conditions. Also. <strong>the</strong> ExtensionService must devote more effort toadvising farmers about <strong>the</strong> relevance of<strong>the</strong>se practices as options for reducingrisks and increasing benefits. thusmaking possible <strong>the</strong> success of wheatproduction in <strong>the</strong> semitropical areas.2.0--------------- ...-------- --- --_....--------.----_...-.--- Areas under recent cultivation- Areas under continuous cultivation(after 4 years soybean-wheat)40 120 180Figure 6. Wheat response to phosphorus application in areas under recentwheat cultivation and after four years of soybean-wheat rotation. Parana.Brazil2.0in <strong>the</strong> soil:2 ppm-0- 5 ppm-0-15 ppm-6-30 ppm0--------0~-------O-------O-6------__650 .100 150Figure 7. Wheat response to phosphorus application in an ozlsol (redlatosol) soil as related to P availability in <strong>the</strong> soil. Parana. Brazil