Ammonia Volatilization from Coated Urea in Paddy Soil of Transplanting Rice Culture

Ammonia () volatilization was measured from latex coated urea (LCU) and normal urea treated rice paddy under transplanting rice culture in Milyang in 2002 and 2003. The volatilization from incubation experiment was significantly related with ammonium-N () concentration and pH in the surface water. The correlation coefficients of volatilization compared to the and pH in surface water were significantly higher in urea than LCU. The volatilization from both urea and LCU treatments was not increased in surface water of pH less than 8.0, while volatilization increased significantly in the surface water of pH over 8.0. The results in the field experiment indicated that volatilization after top-dressing of urea increased rapidly with increasing concentration in soil and floodwater, and highest from 7 to 10 days after top-dressing. The amount of volatilized from urea treatment was in the range of . The variations of volatilization in 2002 and 2003 were caused by changed N dynamics due to the different weather conditions such as rainfall and temperature. The amount of volatilized from LCU treatment was significantly reduced compared to that of urea. The reason for the reduced volatilization in LCU treatment would be due to the lower concentration of in floodwater. The amount of volatilized from LCU treated rice paddy was in the range of , and the loss of N by ammonia volatilization was 2.0-2.3%. Loss of N by volatilization with LCU treatment was reduced by 75-79% comparing to urea treatment.