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.