Abstract:

Based on the data collected through surveys, monitoring and experiments, a study was carried out on nitrogen budgeting of the Huashan Hydrological Experiment Watershed in Chuzhou. A survey on population, crop planting area, fertilization, crop yield, livestock and poultry breeding was conducted and wet deposition of atmospheric nitrogen and nitrogen content in runoff and in grain and in straw were measured and analyzed. Nitrogen budgeting of the watershed in the two irrigation years from October, 2012 to September, 2013 and from October, 2013 to September, 2014 were worked out, and impacts of rainfall and runoff on N budgeting of the watershed were analyzed. Although wet deposition of atmospheric nitrogen was affected by precipitation, in the two irrigation years, the flux of atmospheric nitrogen deposition was 26.10 kg•(hm²•a)^-1 N and 26.32kg•(hm²•a)^-1 N, separately, posing a difference of less than 1%, and the modulus of nitrogen loss with runoff was 3.86 kg•(hm²•a)^-1 N and 8.95kg•(hm²•a^)-1 N, separately, accounting for 6.54% and 13.98% of the total nitrogen output of their respective years, with the latter being over twice as high as the former; chemical fertilizer nitrogen was the main nitrogen input of the watershed, contributing 50.46% and 50.36% to the total nitrogen inputs；nitrogen removal with crop harvest was the main nitrogen output of the watershed, accounting for 56.68% and 52.17% of the total nitrogen output；nitrogen surplus was 59.94 kg•(hm²•a)^-1 N and 55.06kg•(hm²•a)^-1 N separately for the two years. Therefore, it could be concluded that nitrogen loss is related to runoff and that a potential trend towards eutrophication exists in the Huashan Hydrological Experimental Watershed.

Key words: nitrogen budgeting, nitrogen loss, nitrogen cycle, non-point source pollution, hydrological experimental watershed