Nitrogen Wet Deposition and Its Correlation with Ammonia Volatilization Losses from Rice Paddy during Crop Period: A Case Study in Taihu Lake Region

Atmospheric nitrogen deposition is one of the most important sources of nitrogen for surface water and eco-system. Ammonia volatilization is one of the most loss of nitrogen from rice paddy field and sources of atmospheric nitrogen. In order to quantify the nitrogen wet deposition and its correlation with ammonia volatilization losses from rice paddy during rice growth season, field experiments were carried out in high nitrogen input rice paddy in Taihu Lake region. Total wet deposition of total nitrogen, ammonia nitrogen and nitrate nitrogen are 16.04 kg·hm^-2, 7.40 kg·hm^-2 and 3.39 kg·hm^-2 in rice growth season. It equals to 37.7 kg·hm^-2 urea inputs to rice paddy and takes 3835t total nitrogen, 1730t ammonia and 793t nitrate into surface water of Taihu lake. Seasonal ammonia volatilization is estimated to be 95.21 kg·hm^-2, account for 23.6% of seasonal total nitrogen inputs. Urea applications leads to the sharply increase in ammonia volatilization, more than 90% ammonia volatilization emission occurs within one week after urea fertilization. Ammonia and total nitrogen contents in rainfall water are likely relevant to the fertilizer management, but ammonia and total nitrogen were determined both by the precipitation volumes and the nitrogen fertilizer management. Total nitrogen and ammonia nitrogen contents in rainfall water are confirmed high relative to synchronous three-day ammonia volatilization, but not nitrogen wet deposition. Controlled-release urea reduced seasonal ammonia volatilization to 28.97 kg·hm^-2, it is reduced by 69.6% when compared with traditional urea. Widely application of controlled-release urea is efficient to cut off the ammonia volatilization and hence the nitrogen wet deposition.