改进暗管排水条件下氮素分布特性模拟分析

为探究改进暗管排水的环境效应，基于田间试验数据，采用HYDRUS模型对模拟参数进行率定验证，模拟分析长期排水条件下改进暗排与常规暗排的排水特征、排水中的氮素含量以及土壤氮素的分布情况。结果表明，改进暗排作用下土壤硝化作用有所增强，改进暗排具有快速降低地下水位的作用；与常规暗排相比，改进暗排对于氨氮的削减具有较好作用，可减少氨氮46%，但也增加了17%的硝态氮量；对于土壤中氮素分布来说，暗管排水长期作用下，土层铵态氮和硝态氮含量最小值分别位于40~60 cm和20~40 cm土层,模拟结束时土层铵态氮和硝态氮含量最小值仅分别为初始值的5%和10%左右，常规暗排与改进暗排40~60 cm土层的铵态氮含量相差最小，差值仅为0.3 mg·kg^-1，与二者暗管层上部土壤硝态氮含量相差不大。

Simulation of nitrogen distribution characteristics under improved subsurface drainage

In order to explore the environmental effect of the improved subsurface drainage, this project simulated the drainage discharge, nitrogen (N) concentration and the distribution of soil N content under long\|term drainage by improved subsurface drainage system. HYDRUS has been used for parameter calibration and verification based on the field data. The results showed that the soil nitrification increased under improved subsurface drainage system and the improved subsurface drainage could lower groundwater table faster and has better effect on ammonia N reduction. Compared with conventional subsurface drainage, the improved subsurface drainage system made 46% decrease in ammonia N and 17% increase in nitrate N. For the distribution of soil N, under long\|term drainage, the minimum soil ammonia N and nitrate N contents were in 40~60 cm and 20~40 cm soil layer, respectively. At the end of simulation, the minimum soil ammonia N and nitrate N were only at 5% and 10% of initial content, respectively. Compared with conventional subsurface drainage, the soil ammonia N content in 40~60 cm soil layer and soil nitrate N content above the pipe level had small difference of 0.3 mg·kg^-1.