农田地表径流氮素流失特性分析

Characteristics of Nitrogen Losses in Surface Runoff from Farmland

为了了解不同的灌溉条件下水旱农田地表径流氮素流失特性,开展水旱作物节水与传统灌溉条件下农田地表径流氮素流失试验研究。结果表明,不同作物类型对氮素流失影响显著,旱地铵态氮质量浓度低于水田,而硝态氮则高于水田;灌溉方式对氮素流失有一定的影响,但并不显著。虽然节水灌溉农田地表径流氮素质量浓度较高,但由于排水总量大大减少,所以节灌农田氮素流失总量有所减少;降雨对氮素流失影响较为显著,总氮和硝态氮流失随着降雨强度的增加而增加;地形地貌的差异会对氮素流失产生一定影响,表现为下游水稻田块的铵态氮高于上游田块,而总氮和硝态氮则相反;不同生育期地表径流氮素质量浓度不明显。

In order to understand the characteristics of nitrogen losses in surface runoff from upland field and paddy field under different irrigation condition,field experiments were conducted on the nitrogen losses in surface runoff from paddy fields and maize plots under water-saving irrigation and conventional irrigation.The results showed that crop types have significant impacts on nitrogen losses through influencing the plant cover,soil and water conditions in the field.Ammonium nitrogen in dryland is lower than in paddy,but nitrate nitrogen is in contrary;irrigation also affects the losses of nitrogen from farmland by means of influencing the processes of infiltration and retention.Although the concentration of nitrogen under the condition of water-saving irrigation is higher than those of traditional irrigation,the total nitrogen losses in surface runoff from farmlands is reduced significantly by reducing the total surface drainage;rainfall is the most important factor and driving forces for the losses of nitrogen from farmland.The losses of total nitrogen and nitrate nitrogen increase with rainfall intensity;topography and location of field have impacts on rainfall-runoff characteristics,soil erosion and nitrogen losses from farmland.Ammonium nitrogen from the paddy fields in the downstream is higher than that in the upstream,but the total nitrogen and nitrate nitrogen are in contrary.Moreover,the influence of different growing stages on nitrogen losses in surface runoff from farmlands is not obvious.