北京地区冬小麦/夏玉米连作条件下NO_3-N淋失

Nitrate leaching from a winter wheat/ summer maize rotation in Beijing Area

分析评价了北京草甸褐土冬小麦 /夏玉米连作条件下NO3 N累积、淋失以及同氮肥水平的关系。设置 4个氮肥处理 :0、 1 2 0、 2 4 0、 360kgN/ha。在每一处理区 2 0、 40、 60、 80、1 0 0、1 4 0、 2 0 0cm埋设土壤溶液提取器 ,在试验地同期设置两个直径 0 48m、深 2m的原状土柱 ,氮肥水平为 0和 2 4 0kg/ha。土壤剖面取样分析发现 :不施肥种植降低土体NO3 N储量 ,施肥种植增加 0～ 1 0 0cm土体NO3 N储量 ,但只有 360kg/ha才能维持 1 0 0～ 2 0 0cm土体NO3 N储量 ,种植和施肥改变了土壤中NO3 N的含量和空间分布。利用土壤溶液提取器取得剖面2m处土壤溶液NO3 N年均浓度和土柱底部同期排水量估算得到大田不同氮肥水平NO3 N淋失年均通量分别为 :1 8、 2 41、 5 52、 1 7 1 2kg/ha ;施肥处理表观氮淋失百分率为 :0 33 %、 1 0 3 %、3 1 9%。试验结果有益于指导合理施肥和更好地认识农业氮肥应用与地下水NO3 N污染的关系。

This study was conducted to compare NO 3-N cumulation and leaching from a winter wheat/ summer maize rotation under four applied N fertilizer rates of 0,120, 240, and 360 kgN/ha.An array of 7 zero-tension lysimeters installed at 20,40,60,80,100,140, and 200cm below the soil surface in each plot was used to examine NO 3-N leaching; two disturbed soil cores were stalled, one for contrast, the other fertilized with applied N fertilizer rate of 240 kg/ha, to study leacheate and NO 3-N leacheate flux. Soil sampling performed before and after cultivation revealed that contant of soil NO 3-N in unfertilized plots decreased; and N fertilizer applied plots resulted in NO 3-N cumulation in soil of 0～100 cm; but only the fertilized rate of 360 kg/ha could maintain a constant amount of NO 3-N in soil of 100～200 cm. Average cumulative NO 3-N fluxes through the interface of 200cm below the soil surface at four N fertilizer applied rates were 0.18 , 2.41, 5.52 and 17.12 kg/ha; surface percentages of N leaching were 1.24%,1.48% and 3.14% for each fertilized treatment. The findings are beneficial to the determination of economical optimum N rate and the understanding of the potential role of N fertilizer that affects water quality.