降水影响冬小麦灌溉农田水分渗漏和氮淋失模拟分析

A simulative analysis of influence of precipitation on water leakage and nitrogen leaching in irregated farmland

为了研究降水对根层 (1.2m)水分渗漏和氮淋失的影响 ,采用Hydrus 1D模型模拟近 30年实际气候条件下京郊冬小麦田的水氮运移过程。结果表明 ,传统水肥管理 (灌溉量 2 70mm ,施氮量 15 0kg·hm-2 )冬小麦农田 ,降水量小于 5 0mm时 ,水分渗漏量均值为 5 .0mm ;降水量在 5 0～ 10 0mm ,对应水分渗漏量均值为 2 3.6mm ;当降水量为10 0～ 15 0mm或大于 15 0mm时 ,平均水分渗漏量为 36 .9或 12 5 .6mm。对应的氮淋失量分别为 1.5、5 .8、9.6和 4 0 .4kg·hm-2 。水分渗漏及氮淋失主要发生在冬小麦返青期和拔节期灌溉后 ,因此应减少早期灌溉量并应避免过早施肥。水分渗漏量可表示为降水指数的指数函数 ,而氮淋失量则与水分渗漏量呈线性相关。在可预测降水条件下 ,文中给出的经验关系式可用于估测水分渗漏量和氮淋失量。

Climatic factors have evident influences on water and nitrogen behavior and their validity for crop in root zone. The research focused on the influence of precipitation on water leakage and nitrogen leaching in irrigated winter wheat field. The model of Hydrus 1D was used to simulate water movement and nitrogen transport under variable climate of 30 years with winter wheat in suburb of Beijing . The result showed that water leakage and nitrogen leached in irrigated wheat filed were little. When precipitation was less than 50mm, possible water leakage was 5.0mm; it was 23.6mm when Precipitation was between 50 and 100mm; Precipitation was between 100 and 150mm, it was 36.9mm; Precipitation was more than 150mm, it was 125.6mm. And corresponding nitrogen leached were 1.5? 5.8? 9.6 and 40.4kg·hm -2 . It was incidental to water leakage and nitrogen leaching after irrigation during earlier growth period. Therefore, irrigation amount should be reduced and fertilization should be avoided at the stage. The quantity of water leakage was exponential function of precipitation index and was linearly relative to the amount of nitrogen leached. Water and nitrogen leached could be evaluated by the experiential equations provided in the article with the predicted precipitation.