降雨强度对三峡库区坡耕地土壤氮、磷流失主要形态的影响

揭示紫色土坡耕地在不同降雨条件下对土壤养分流失及其环境效益的影响,对于保护三峡库区水环境具有重要意义。通过径流场试验分析2010年5月1日-7月10日6次降雨过程中紫色土坡耕地的氮、磷流失特征。结果表明:大雨时产生的径流量分别为中雨和小雨时的2.34,7.59倍,同时大雨产生的径流中TN、TP含量高于小雨和中雨时,大雨导致的氮、磷流失远远超过中雨与小雨。大雨时产生的累积泥沙量分别是中雨和小雨的8.34,111.38倍。紫色土坡耕地径流中TN、TP的主要形式是有泥沙携带的颗粒态氮、磷,降雨量越大,颗粒态氮、磷的比例越高。中雨产生的径流中颗粒态氮占TN的74.9%～75.9%,大雨产生的径流中颗粒态氮占TN的比例更高,达到85.0%～92.6%。颗粒态磷是径流中磷的主要形态,大雨、中雨、小雨产生的径流中颗粒态磷占TP的比例分别为96.6%～97.7%,93.9%～96.2%,90.5%～94.4%。紫色土坡耕地氮、磷流失主要是以泥沙为载体,这在降雨量较大时表现得尤为明显。控制坡耕地氮、磷流失应着重考虑控制降雨量较大时的氮、磷流失。

Main Features of the Loss of Nitrogen and Phosphorus and Rainfall Intensity Influence in the Slope Farmland of the Three Gorges Reservoir Area

It is important to protect the water environment of the Three Gorges Reservoir Area that revealing the influence of the soil nutrient loss in slope farmland of purple area and environmental benefit under different conditions.This paper analyzed features of the loss of nitrogen and phosphorus in slope farmland of purple area for six times rainfall during the time from May 1 to July 10,2010.The results showed that the runoff volume produced in heavy rain was 2.34 times in moderate rain and 7.59 times in light rain,meanwhile the contents of TN and TP produced in heavy rain were higher than in moderate rain and light rain,as well as the loss of nitrogen and phosphorus.Accumulated sediment produced in heavy rain was 8.34 times in moderate rain and 111.38 times in light rain.The man forms of TN and TP in slope farmland of purple area runoff were granular nitrogen and phosphorus brought by sediment.The more rainfall had,the higher proportion of granular nitrogen and phosphorus enjoyed.Granular nitrogen in runoff produced in moderate rain was 74.9%~75.9% of TN,and higher in heavy rain,reaching 85.0%~92.6%.The main form of phosphorus in runoff was granular phosphorus,which proportion in TP was 96.6%~97.7% in heavy rain,93.9%~96.2% in moderate rain and 90.5%~94.4% in light rain.The loss of nitrogen and phosphorus in slope farmland of purple area with sediment as the carrier,this was profoundly manifested in the time of heavy rainfall.To control the loss of nitrogen and phosphorus during the heavy rain should be taken into consideration the control of the loss of nitrogen and phosphorus in slope farmland.