[目的]研究紫色土丘陵区水稻–大白菜轮作模式下,大白菜季产量、氨挥发损失通量及影响因素,可为四川省紫色土丘陵区农业面源污染防治提供技术支撑.[方法]以大白菜为试材进行了田间试验.结合当地农民的施肥习惯,设定了6个施氮肥水平,施氮量依次为N 0、112.5、150、187.5、225、300 kg/hm2,氮肥均等量分为基肥和追肥,分两次施用.采用密闭室连续通气法对大白菜地进行田间原位氨挥发测定.测定在基肥和追肥施用之后的第1天开始,上午9:00—10:00,下午16:00—17:00进行测定,连续测定14 d(降雨停止测定),直至检测不到氨挥发.成熟期调查大白菜产量和全氮含量.[结果]大白菜季施氮总量从0增加至300 kg/hm2时,单季氨挥发损失总量由2.27 kg/hm2增加至22.72 kg/hm2.基肥和追肥施氮量分别从0增加到150 kg/hm2时,基肥后氨挥发总量的变化范围为1.08 kg/hm2到23.58 kg/hm2,显著高于等量追肥后的氨挥发总量(0.21～2.83 kg/hm2),这与基肥施用时期温度高于追肥施用时期的温度有关.随施氮量增加,大白菜产量增加,但从N 187.5 kg/hm2增加至300 kg/hm2时,大白菜产量增加不显著;氨挥发总量随施氮量增加而增加,但150 kg/hm2与187.5 kg/hm2处理差异不显著,187.5 kg/hm2与225 kg/hm2、300 kg/hm2处理之间差异显著.[结论]大白菜季氨挥发主要集中在施肥之后的两周之内,施肥量和温度是影响大白菜季氨挥发的主要因素.综合考虑产量和单季氨挥发损失总量等因素,施氮肥量为N 187.5 kg/hm2时,大白菜的产量和环境效益最佳.%[Objectives]Many factors affect cabbage yield and ammonia volatilization in rice–cabbage rotation system in purple soil. The research was aiming to clarify the trends of NH3 volatilization affected by nitrogen rates and climate factors, to give some recommendation for mitigating nitrogen loss in Sichuan Province.[Methods]Field experiments were conducted with different nitrogen rates on cabbage in a purple soil. The nitrogen rate included N 0, 112.5, 150, 187.5, 225 and 300 kg/hm2. The N fertilizer was divided into two equal parts and applied for basal application and topdressing. A continual air-flow chamber method was used to measure the ammonia volatilization. The measurement was conducted successively for 14 days after basal fertilization or topdressing at 9:00–10:00 am and 16:00–17:00 pm till no ammonia volatilization was detected. The cabbage yield and nitrogen content in the cabbage were measured after maturity.[Results]The total NH3 volatilization of the entire season increased from 2.27 kg/hm2 to 22.72 kg/hm2 with increasing nitrogen rate from 0 to 300 kg/hm2. When the nitrogen rate was increased from 0 to 150 kg/hm2, NH3 volatilization after basal fertilization was in range of 1.08–23.58 kg/hm2, greater than that after topdressing (0.21–2.83 kg/hm2), which was due to the higher temperature after basal fertilization than after topdressing. Cabbage yield increase became not significant when the N rate was over 187.5 kg/hm2, however, the total NH3 volatilization kept increased. The NH3 volatilization increase was not significant when the N rate was increased from 150 kg/hm2 to 187.5 kg/hm2, but became significant from 187.5 kg/hm2 to 225 kg/hm2 or 300 kg/hm2.[Conclusions]Ammonia volatilization of cabbage occurs largely during the first two weeks after fertilization. Nitrogen rates and soil temperature are the two main factors affecting ammonia volatilization. Comprehensively considering the yield and N loss, the optimal total nitrogen rate is 187.5 kg/hm2.
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