Characteristics of ammonia volatilization on rice grown under different nitrogen application rates and its quantitative predictions in Erhai Lake Watershed, China

Ammonia (NH3) volatilization was measured with the continuous airflow enclosure chamber method under different urea application amounts using pots in paddy fields in Erhai Lake Watershed, China. Several factors, such as the urea nitrogen application amount, days after fertilization, NH4 (+)-N concentration and pH of surface water, and climate, that could affect ammonia volatilization were also studied. The results indicated that ammonia volatilization loss increased linearly with increasing amounts of applied urea. The ratios of the ammonia volatilization loss to the applied nitrogen ranged from 16.59 to 18.43 % with different nitrogen application amounts. The ammonia volatilization loss peaked within the first 3 days after fertilization, which accounted for 65-82 % of the total ammonia loss in each period. We observed the following degree of the effects of various factors on ammonia volatilization: NH4 (+)-N concentration of surface water > urea application amount > pH of surface water > days after fertilization > water temperature of surface water. The wind velocity and rainfall were the key factors affecting ammonia volatilization. The model of ammonia volatilization flux was established by using the measured dates from 2013 and was represented as Y = 0.008(x(1) + x(2) + x(3)) + e(0.056x4-0.068x5)-0.623 (R (2) = 0.81, P < 0.0001). The model was verified by using the measured dates from 2012. The calculated values fitted well with the field observations. However, the model parameters need to be amended using the model to predict the ammonia volatilization flux in the rice season from other regions.