丹江口水库农业径流小区土壤氮磷流失特征

Nitrogen and Phosphorus Loss Characteristics from Agricultural Runoff Plots in the Danjiangkou Reservoir

通过对丹江口水库小流域雨季（2013年8月）观测的降雨—径流农业小区试验数据,分析不同种植作物下农田地表产流规律,研究土壤氮磷流失特征,为库区农业面源污染控制提供依据。结果表明,农业小区径流总磷（TP）含量在0.13-0.82mg/L之间,颗粒态磷（PP）占TP比例超过60%,径流中TSS与PP也呈现极显著相关（p〈0.01）,表明磷素流失主要以颗粒态流失为主。径流总氮（TN）含量范围为0.7-4.7mg/L之间,TN流失量与硝态氮极显著相关（p〈0.01）,径流中硝态氮占TN比例也超过了50%,表明硝态氮是地表径流无机氮流失的主要成分。25°玉米、15°荒地径流小区的氮流失率超过了1.5%、磷流失率超过了0.12%,高于其它类型的小区,可能与这2种小区高坡度、低植被覆盖度有关。土壤氮的流失风险要高于磷,是面源污染的主要控制目标。利用梯田种植作物,同时在坡地上形成相对较高的植被覆盖密度是减少这一地区土壤养分流失有效手段。

Ten typically agricultural runoff plots in the Danjiangkou Reservoir area were selected to analyze the runoff characteristics and loss amount or rate of nitrogen and phosphorus during a flooding season, which provided guidelines for controlling agricultural non-point source pollution in this region. The concentrations of total phosphorus （TP） in the runoff ranged from 0.13 mg/L to 0.82 mg/L. The percentage of particulate phosphorus （PP） to TP were more than 60% in the runoff and there was a significant correlation between PP and total suspended solids （TSS） （p〈0.01）, indicated that phosphorus loss in the runoff was mainly originated from in particulate fraction. The concentrations of total nitrogen （TN） ranged from 0.7 mg/L to 4.7 mg/L, while nitrate nitrogen dominated the nitrogen fraction （more than 50%）. The loss rates of nitrogen and phosphorus in the agricul- tural runoff plots of weed land in 15 degree and corn land in 25 degree both exceeded 1.5% and 0.12%, respectively, which probably owing to the high slope and low vegetation cover of the plots. It was concluded that the potential risk of nitrogen loss was higher than phosphorus, and nitrogen should be taken as the main control target in Danjiangkou Reservoir area. Therefore, forming a relatively high vegetation cover on the sloping land was an effective method to reduce the nutrient loss of soil, especially for nitrogen.