模拟降雨条件下太湖地区稻田氮素径流流失特征

为了解太湖水网地区稻田氮素径流流失特征,在不同施肥处理试验小区的不同时期,进行人工模拟降雨试验.结果表明,降雨后稻田总氮(TN)流失量随着施氮量的增加而增加,施氮初期是氮素流失高峰期.第一次施氮后5 d(降雨前有田面水),0、225、300和375 kg/hm~2 4种施氮水平的稻田TN流失量依次递增,依次相差均在0.15kg/hm~2以上;第二次施氮后15d(降雨前无田面水),施氮量对TN流失量影响不大,各施氮水平的稻田TN流失量依次相差均在0.05 kg/hm~2以下.氮素流失形态以硝态氮和铵态氮为主,在第一次施氮后3d的稻田径流TN中,铵态氮和硝态氮所占比例近50%.此外,在一次降水过程中,无论降雨前有无田面水,产生径流的初期都是氮素流失的高峰期.

Nitrogen Loss Characteristics with Runoff under Simulated Rainfall Conditions in Paddy Field of Taihu Lake Region

The aim of this paper is to understand characteristics of nitrogen (N) losses with runoff from paddy field in Taihu Lake region. Simulated rainfall experiments were carried out in paddy field at different N fertilizer treatments and different times. The results indicated that: amount of N losses after rainfall increases as N fertilizer application, and the beginning period of N fertilizer application was the peak period of N losses. After 5 days of N fertilizer application (there was surface water in paddy field before the simulated rainfall experiment was carried out), amount of N losses with runoff from paddy field increase as 4 N fertilizer application level with 0,225,300 and 375 kg·hm~(-2), and the difference was above 0.15 kg·hm~(-2) in sequence. After 14 days of N fertilizer application (there was no surface water in paddy field before the simulated rainfall experiment was carried out), amount of N fertilizer application affected that of N losses little, and the difference was under 0.05 kg·hm~(-2).The proportion of NH_4~+-N and NO_3~--N in TN which losses from paddy field was nearly 50%.In addition, no matter whether there was surface water in the paddy field before rainfall,the early stages of runoff was the peak period of nitrogen losses.