Loss characteristics of agricultural non-point source pollutants under controlled drainage

The contrast test of monitoring uncontrolled drainage and controlled drainage were carried out at the Qing Tong Xia Irrigation District in Ningxia Hui Autonomous Region. The concentration and load variation characteristics of salinity, total phosphorus, nitrate-nitrogen and ammonia-nitrogen in farmland drainage under controlled drainage condition were analyzed, and the mechanism of reducing drainage and sewage was discussed. The results showed that comparing to uncontrolled drainage, with controlled drainage, the drainage amount would reduce by 43.01%, the concentration of salinity, total phosphorus, nitrate-nitrogen and ammonia-nitrogen would reduce by 7.68%, 17.39%, 18.16%, 9.20% respectily, and the pollution load would reduce by 46.49%, 44.46%, 57.51%, 38.89% respectively. The reduction of pollution load results from joint actions of drainage reduction and pollution concentration decrease. The drainage reduction plays the leading role and pollutant concentration decrease is the secondary factor.