[Impacts of Nitrogen Application on Ammonia Volatilization During Maize Season in Northern China]

Ammonia volatilization is one of the major paths of nitrogen (N) loss and may exert a substantial impact on air quality. This study aims to explore the effects of nitrogen (N) fertilizer types, fertilization rate, and application timing and gas collection method on NH₃ volatilization during the maize season in Northern China. This study collected the publications on the NH₃ volatilization from maize farming which were conducted in Northern China from 1980 to 2018, and undertook a systematic analysis. The study found that with the increase of N rate, the total and net NH₃ volatilization at the basal and topdressing fertilization stages increased at exponential and power function, respectively. When the ratio of basal/topdressing N rate was 1/1, the total and net NH₃ volatilization during the topdressing stage (58.4% of the whole season emission) was significantly higher than that in the basal fertilization stage (41.6%) (P<0.05). The priming effect first showed a negative effect and then gradually turned into a positive effect with the increase of N rate. Due to the positive priming effect, the net NH₃ volatilization, without considering the priming effect, was overestimated under the conventional N application (>297 kg·hm^-2). There is a significant difference between the NH₃ volatilization measured by the venting method and the sponge absorption method, and the data from the venting method are more stable (P<0.01). Compared with conventional urea, slow-release urea may reduce NH₃ volatilization by 20% to 50%. Control fertilizer N rate at the topdressing stage is more efficient in reducing the NH₃ volatilization from maize production in Northern China, and the venting method is more suitable for the quantification of NH₃ volatilization than the sponge absorption method under a high rate of fertilizer N.