农田土壤中氮的环境指标研究

氮肥的大量不合理施用使农田氮素成了农业面源污染的重要因子,然而关于农田氮素对环境污染的标准并没有系统的介绍。笔者分别从农田土壤氮素盈余、农田径流总氮、铵态氮、硝态氮等方面着手,介绍农田土壤中氮对环境产生的影响。土壤中氮素富集会加大农田土壤氮流失至水体的风险和数量。农田生态系统中氮素通过氨挥发、地表径流、下渗淋失等进入到环境,其盈余主要以气态、可溶态等形态对环境造成污染。综述国内外相关研究得到:农田径流损失的氮以可溶态为主,其中水稻田面水氮浓度超过30 mg/L会促使土壤矿质态氮部分释放,增加土壤溶液中矿质态氮含量,增加农田土壤氮流失风险;土壤无机N含量达到60 mg/kg时能满足作物的正常生长,超过此值,N素流失风险增加,多余的土壤NO3-N将会引起较大的环境风险。化肥使用量控制在150~180 kg/(hm~2·a)之内,可以有效控制化肥氮的损失污染。土壤氮素盈余、农田径流总氮、铵态氮、硝态氮等可作为农田土壤中氮的环境指标。

Environmental Indicator of Soil Nitrogen in Farmland

Nitrogen plays a vital role in agricultural production.With a large number of unreasonable application of fertilizer, nitrogen in the farmland has become an important factor of agricultural non-point source pollution.Loss of soil nitrogen and nitrogen farmland pay significant impact on the ecological environment.Soil Nitrogen surplus, Agricultural runoff TN, ammonium and Nitrate, can reflect different aspects of the impact of nitrogen on the environment.With the increasing amount of nitrogen fertilizer in the soil has progressively enriched with nitrogen, farmland nitrogen loss increased the risk and the number to water bodies.Nitrogen nutrient surplus witch is closely related to agricultural production is an indicator of environmental quality. With the rapid development of agriculture, an excess of nitrogen fertilizer run into the ecosystem, that become a burden on the environment. Its main earnings losses into the environment in various forms, has become an important source of non-point source pollution.Farmland nitrogen runoff loss in soluble fraction. When paddy field surface water and nitrogen concentration exceeding 30 mg/L, it will lead to the release of part of the soil mineral N, witch will lead to the release of part of the soil mineral N, increase mineral nitrogen content in soil solution.