涂层尿素在石灰性土壤上的行为

本项试验主要探索涂层尿素在石灰性土壤上的变化规律。试验结果表明，在三种不同水分含量条件下（10％、15％、20％），涂层尿素施入土壤后氨挥发速率均比普遍尿素低;涂层尿素施入土壤随即浇水，有良好的随水移动性能，肥料氮在土体中的移动深度和肥料氮的回收率随浇水量的不同表现出明显的差异;涂层尿素肥料氮的回收率比普通尿素高2.28个百分点。涂层尿素做底肥时，在小麦上的利用率比普通尿素高3.4个百分点，在玉米上高5.18个百分点;底、追结合施用涂层尿素在小麦上的利用率比普通尿素高5.6个百分点，在玉米上高9.5个百分点。涂层尿素在小麦和玉米上施用，其氮素的损失率比普通尿素低5.4～11.4个百分点。在种植小麦条件下涂层尿素施入土壤后，肥料矿化和供氮特征表现为小麦生长前期0～40Cm土层中速效氮含量低于普通尿素，小麦起身拔节以后，速效氮含量则高于普通尿素。

BEHAVIORS OF COATED-UREA IN CALCAREOUS SOIL

The experiments of decomporsition, transformation and mineralization of coated-urea and common urea were conducted in calcareous soil. Results showed that the rate of ammonia volatilization of coated-urea was lower than common urea under different water content conditions (10%. 15%. and 20%). The N moved down in soil easy after coated-urea applied and watered. The movement dipth and recoery rate of N were different with different water content. and the recovery rate of coated-urea increased by 2. 28% than common urea. The nitrogen use efficiency of coatod-urea was also higher than common urea, the absorption rate increased ty 3. 4% for wheat and by 5 .18% for corn when coated-urea appiled as basal. Coated-urea applied to wheat and corn as basal comblned top dressing the increase rate was 5. 6% and 9. 5%, respectively.The N loss rate of coated-urea was 5. 4%～11. 4% lower than common urea in wheat-corn cropping system.EXperiment of N mineralization and supply capacity showed. the available N release of coated-urea was lower than common urea in 0～40cm soil layer at early growing Stage of wheat, the NO₃^--N increase significantly after elongation of wheat and could meet the need to nitrogen for wheat growth.