中文摘要：

通过埋设土壤溶液抽滤器采集渗漏水样，对上海郊区大田条件下稻麦轮作系统中土壤氮素（N）的渗漏流失情况进行了观测研究．研究结果表明，稻季渗漏水中总氮（TN）浓度随时间呈下降趋势，其中，硝态氮（NO3^--N）由泡田初期的10mg·L^-1以上迅速下降至2mg·L^-1以下，铵态氮（NH4^＋-N）则始终低于1．3mg·L^-1．施肥能引起渗漏水N素增加；稻田淹水过程也通过改变土壤氧化还原环境控制着N素形态的转换．麦季施肥小区渗漏水中N素形态以NO3^--N为主，且施肥后迅速上升到平均7．11mg·L^-1；NH4^＋-N浓度在施肥和不施肥处理中均很低，分别为0．38mg·L^-1和0．36mg·L^-1．在稻季施肥2．50×10^4kg·km^-2和麦季施肥2．14×10^4kg·km^-2（以N计）的情况下，N素淋失负荷分别为6．08×10^2kg·km^-2和7．42×10^2kg·km^-2，分别占施肥量的2．4％和3．5％；施肥条件下两季总的N素淋失负荷比不施肥处理高出108．7％．

英文摘要：

A field case study was conducted to elucidate the dynamic characteristics and the load of N leaching in paddy-wheat rotation fields during one year planting. The results showed that total nitrogen （TN） in natural leaching water declined significantly during the paddy season. Nitrate （ NO3^- -N） fell rapidly at the first several days of immerging, which was from more than 10 mg· L^ -1 to under 2 mg· L^ -1. Ammonia nitrogen （ NH4^＋ -N ） kept at a low level （ 〈 1.3 mg· L^ -1 ）. Flush irrigation, which changed the oxidation-reduction potential of paddy soil, as well as fertilizer application, both had great effect on the N concentration in leaching water. Along with the prolonged flooding, NO3^- -N decreased dramatically and NH4^＋ -N increased slightly. NO3^- -N was the dominant species in wheat season, and it rose quickly after fertilizing （ average 7.11 mg· L^ -1）. NH4^＋ -N concentration was low in wheat season, as in fertilizing plot it was 0.38 mg· L^ -1 , and in control plot was 0.36mg· L^ -1. Under the conditions of an application rate of 2.50 × 10^4 kg· km^ - 2 in paddy season and of 2.14 × 10^4 kg· km^ -2 in wheat season, the N leaching loads were 6.08 × 10^2 kg· km^ -2 and 7.42 × 10^2 kg· km^ -2 separately, and were 2.4% and 3.5% of total fertilizer application. In one year planting, the N leaching load in fertilizing plot was 108.7% higher than in control plot.