不同尺度稻田氮磷排放规律试验

为研究不同尺度稻田氮磷负荷排放规律及其原因，在湖北省漳河灌区选取封闭性较好且逐级嵌套的6个尺度，于2009年5－9月水稻生育期监测各尺度试区进出口水量，并采集排水水样进行氮磷浓度化验。结果表明，稻田氮磷排放负荷随着尺度的增大而降低，即存在尺度效应。总氮、铵态氮、硝态氮、总磷、颗粒态磷、可溶磷的排放负荷从田间尺度到小流域尺度分别下降80.5%、73.4%、39.7%、73.8%、75.0%、50.0%。氮磷排放负荷产生尺度效应的原因是：塘堰、沟渠对氮磷的去除和排水的重复利用。因此，对于农田氮磷排放对下游水体污染的评价应考虑其尺度效应。

Experiments on nitrogen and phosphorus losses from paddy fields under different scales

In order to analyze loss laws of nitrogen and phosphorus from the rice farming system under different scales, six nesting scales composing of subbasins were selected for water balance analysis as well as nitrogen and phosphorus losses monitoring during rice growing season in Zhanghe Irrigation Area, Hubei Province. Water quantity of inlet and outlet of different scales were measured and water samples were collected for nitrogen and phosphorus analysis at the same time during the whole rice growing season from May to September in 2009. The results showed that there was scale effect in the process of nitrogen and phosphorus losses from the rice farming system. The loss loads of total nitrogen, ammonia nitrogen, nitrate nitrogen, total phosphorus, particulate phosphorus and dissoluble phosphorus decreased by 80.5%, 73.4%, 39.7%, 73.8%, 75.0%, and 50.0% from field to watershed scale, respectively. The reason of scale effect was caused by removal the effect of nitrogen and phosphorus pollutants in both ponds and drainage ditches and the reuse of drainage water. The scale effect should be taken into consideration when evaluating the contribution of nitrogen and phosphorus pollution loads from farmland to river body.