Nitrogen and Phosphorus Runoff Losses from Farmland as Affected by Cropping Pattern during Flood Season

The rainfall-runoff experiment in flood season of 2007 was conducted to evaluate the effects of cropping pattern on cumulative surface runoff,erosion,and nitrogen and phosphorus losses in surface runoff,and to assess the nitrogen and phosphorus concentration component of different cropping pattern.The results indicate that Compared to bare plot,the cumulative runoff in cotton and soybean plots decreased by 21.1% and 49.5%,the cumulative erosion of those decreased by 49.5% and 71.1%,and cumulative nitrogen and phosphorus losses in surface runoff reduced significantly.Cumulative dissolved nitrogen and phosphorus losses in runoff were closely related to cumulative runoff,while Cumulative particular nitrogen and phosphorus losses in runoff were closely related to cumulative erosion.Dissolved nitrogen and phosphorus constituted the major proportion of total nitrogen and phosphorus in runoff from cotton and soybean plots.To plant cotton and soybean in Huaibei plain was effective in reducing nitrogen and phosphorus losses.