Ammonia Volatilization from Pit Wall under Different N Top-addressing from Water Storage Irrigation Pit in Apple Orchard北大核心CSCD

【Objective】Water storage pit is a common technology to bank precipitation for irrigation in arid region. In this paper, we studied ammonia volatilization from the wall of the pits under different N top-addressing in an apple orchard.【Method】We compared seven nitrogen top-addressing in the experiment: topdressing 600, 300 and 0 kg/hm2 at anthesis stage and fruit enlargement stage respectively. The ammonia volatilization from the wall of the water storage pit was measured using glycerophosphate-ventilation. We analyzed the dependence of ammonia volatilization on soil ammonium, soil nitrate, soil temperature, air temperature and humidity respectively.【Result】Ammonia volatilization increased with the topdressing amount after irrigation and fertilization. Top-addressing after anthesis stage could prolong ammonia volatilization for a significant period with a peak within 52.93 to 576.80 mg/(m2·d) occurring 3~5 days after the top-addressing. Top-addressing during fruit enlargement stage resulted in a short period of ammonia volatilization with a peak within 81.11 to 1 047.79 mg/(m2·d) occurring two days after the top-dressing. The accumulated ammonia volatilization (calculated by N) after one-off topdressing after anthesis stage and fruit expansion stage was 3 332.88~7 052.01 mg and 2 178.14~5 126.97 mg respectively. Compared to one-off topdressing, two top-addressing reduced ammonia volatilization to 2 013.21~ 4 642.11 mg, 34.17%~39.60% lower than that under one-off topdressing after the anthesis stage. Ammonia volatilization from the water storage pit wall accounted for 0.57%~1.40% of nitrogen loss, being the highest under one-off topdressing at anthesis stage followed by one-off topdressing at fruit expansion stage. Ammonia volatilization was positively correlated with soil ammonium and air temperature (P<0.05). Soil temperature and nitrate also played a role in ammonia volatilization. Rise in air humidity and rainfall after fertilization can reduce ammonia volatilization, and the dynamical change in accumulated ammonia volatilization can be well described by the Elovich dynamic equation, in which the rate constant parameter was positively correlated to the amount of top-addressing nitrogen and negatively correlated to soil temperature, both at significant level.【Conclusion】Ammonia volatilization from water storage pit wall can be controlled by managing the amount of fertilizer application and time at which the fertilizer was applied. Our results suggested that reducing the top-addressing amounts and top-addressing twice can effectively reduce nitrogen loss via ammonia volatilization. © 2019 Authors. All rights reserved.