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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。
A large number of irrational application of nitrogen fertilizer made farmland nitrogen an important factor of agricultural non-point source pollution. However, there is no systematic introduction about the standard of farmland nitrogen for environmental pollution. The author introduces farmland soil nitrogen surplus, farmland runoff total nitrogen, ammonium nitrogen, nitrate nitrogen and so on separately, introduces the farmland soil nitrogen to the environment influence. Nitrogen enrichment in soil increases the risk and amount of soil nitrogen losses to farmland. Nitrogen in farmland ecosystem enters the environment through ammonia volatilization, surface runoff and infiltration loss, and its surplus mainly pollutes the environment in the form of gas and soluble. This paper summarizes the relevant research at home and abroad that the loss of runoff from farmland is dominated by soluble nitrogen, of which the surface water N concentration in paddy rice exceeds 30 mg / L, which will lead to the partial release of mineral nitrogen in soil, increase the content of mineral nitrogen in soil solution, Soil nitrogen loss risk; soil inorganic N content of 60 mg / kg to meet the normal growth of crops beyond this value, N loss of increased risk of excess soil NO3-N will cause greater environmental risks. The amount of fertilizer used is controlled within 150 ~ 180 kg / (hm ~ 2 · a), which can effectively control the loss of fertilizer nitrogen. Soil nitrogen surplus, farmland runoff total nitrogen, ammonium nitrogen, nitrate nitrogen can be used as farmland soil nitrogen environmental indicators.