Effects of Nitrogen Rate and Field Water Nitrogen Content on Ammonia Volatilization from Paddy Field in a Purple Soil Hilly District

The effects of different N application rates(0, 112.5, 150, 187.5, 225 kg/hm2), as well as paddy field water N content on NH3 volatilization characters were studied in a paddy field in the purple soil district by using a closed air-flow chamber method. The results indicated that NH3 volatilization rate peaked during the first 1 – 3 days after N fertilizer application and decreased gradually thereafter. Higher NH3 volatilization rates were observed in the high N application treated plots. The amount of NH3 volatilization during the observation duration increased with the increase of N fertilizer application rate. Significantly correlativity(y = 0.312 3 x + 24.712 9, r = 0.916 6***) was found between NH3 volatilization and N fertilizer application rate. The ratio of N loss via NH3 volatilization to N fertilizer application rate ranged within 29.4% – 38.0%. NH4+-N, dissolved N and total N concentrations in field water which showed a sharp increase after N fertilizer application were highly related to NH3 volatilization, with the highest correlation efficient 0.926 9, 0.841 2 and 0.881 3, respectively. Improved fertilizer application techniques such as incorporation of organic material with chemical fertilizer, utilization of controlled release chemical fertilizers and N fertilizer management during the rice growing season are required to decrease NH4+-N, dissolved N and total N concentrations in field water to mitigate NH3 volatilization in paddy field in the purple soil hilly district.