宁夏黄灌区退水过程中氮污染特征模拟

Simulation of Nitrogen Pollution Characteristics in the Return Water of Ningxia Irrigation District

宁夏黄灌区是我国商品粮生产基地之一,农业高强度和化肥高投入对灌区水环境和黄河水安全造成了严重威胁。农田退水中氮素迁移流失的网室土柱模拟实验表明：1每次施肥1~2d后（穗肥是1周后）,田面水中全氮量均出现峰值,不断下降后逐渐趋于稳定,全氮量随时间的变化符合对数衰减规律;23次施肥后,种植水稻的土柱各土层渗漏水中的全氮量高于未种植水稻的土柱,水稻根系的发育,一定程度上促进了氮素向下迁移,加剧了氮素流失的风险,水稻收获前控制氮的渗漏损失尤为重要。

Ningxia Irrigation District is one of the commodity grain production bases in China.The high strength of agriculture and high input of fertilizer have serious threats to the water environment of irrigation region and the safety of the Yellow River.Soil column experiment in net room was conducted to simulate the law of nitrogen migration and losing in the return flow of farmland.Main conclusions were that：1Total Nitrogen（TN）in surface water reached peaks at 1~2dafter each fertilization（except for panicle fertilization which was one week）,then gradually decreased and tended to be stable.The changes of TN over time were accordance with logarithmic decay.2After three times of fertilization,TN of seepage water in planted rice column was higher than that of not-planted rice column.The development of rice roots contributed to the downward migration of nitrogen and increased the risk of nitrogen loss.It is particularly important to control the nitrogen loss before the rice harvest.