Study On The Agricultural Non-point Source Pollution Of Liaohe Source Area

With the development of agricultural modernization and the large application of pesticide and fertilizer, the agricultural non-point source pollution has become the major concern nowadays, and the main source of water pollution and eutrophication. Jilin Province is an important commodity grain production bases, the annual fertilizer application is about 203.8 tons, and the average fertilizer application is about 34.9 Kg per mu, which is above the average of the nation and the world. The agricultural water withdrawal running into the tributaries and the main stream contributes to the non-point pollution in the river basin. Compared with other provinces, Jilin Province has its own characteristics in terms of climate, topography, hydrology, soil, economic status, and so on, which determines that the non-point pollution in Jilin has a very distinct characteristics. Thus, the study on the agricultural non-point pollution is of great significance.The study site is Quanyong watershed of Liaohe source area. Considering the runoff, the tillage and slope, the author analysed the charateristics of nitrogen and phosphorus losses, and simulates the nitrogen and phosphorus losses with the application of AnnAGNPS model. The conclusions are as follows:(1) the design of the test zones are the bare land with a slope of 4.8°, the terrace with a slope of 5.2°, the longitudinal ridges with a slope of 5.5°, and the cultivated land with a slope of 6.5°. The analysis of nitrogen and phosphorus in the runoffs after the rainfall shows that the nitrogen loss and phosphorus loss are mainly in forms of dissolved nitrogen and particulate phosphorus. The sequence of the nitrogen and phosphorus loss intensity is, the longitudinal ridge (5.5°)>the bare land (4.8°)>the cultivated land (6.5°)>the terrace (5.2°). More runoff, faster the N and P loss. Sloper, more loss. More complexed cultivated mode, less loss.(2) Through the study on the N and P loss after the rainfall, and the input of N and P in the Huizhong River and Quanyong River from March to October in 2009, the author proves that the N and P loss in Spring is more than that in Summer. The main cause is the first rainfall during the fertilization in Spring, which brings large amounts of fertilizer into the river.(3) AnnAGNPS model could simulate the N and P load under the condition of rainfall. The simulation results show that the deviation of ammonia simulated values is less than that of the TP. The study proves the fesibility of AnnAGNPS model in Liaohe River Basin.The study draws the countermeasures of agricultural non-point pollution in Liaohe River Basin, accordingly.