Study On Nitrogen, Phosphorus Losses Feature And Factors From Agricultural System In Chao Hu Lake Catchment

The serious eutrophication has appeared in Chaohu Lake because of water pollution and that has resulted in the reducing of biodiversity, the loss of economic and the destruction of ecological environment. This phenomenon was not considered to be the contribution of point source pollution in the industry due to effective control of waste drainage, but to be non-point source pollution in the agriculture, in which overland runoff of rainfall and irrational fertilization in agricultural planting played a main role in eutrophication of Chaohu Lake. Therefore, it is very important for mastering of relevant information about non-point source pollution in Chaohu Lake to release and control the water pollution in the Lake.In this work, the characteristics of overland runoff about the typical paddy field and arid land in Tongda Town, Lujiang County which belong to Chaohu Lake area, were investigated. The method of in-spot monitoring combined indoor soil-column leaching experiments was applied to study the rule of the loss of nitrogen-phosphorus fertilizer about the land-use types, the rainfall intensities and the fertilization way. The results showed that:In the typical agricultural system, the amount of nitrogen-phosphorus loss in arid field is higher than that of farmland, and it has obvious seasonal characteristics, which displayed that the peak output season of nitrogen-phosphorus is in summer and autumn. The great concentration for total nitrogen was gotten to 8.233 mg/l, for total phosphorus to 3.00 mg/l, and ammonia nitrogen to 4.113 mg/l in arid land, and the great concentration for total nitrogen was to 6.008 mg/l, total phosphorus to 0.467 mg/l, and ammonia nitrogen to 3.484 mg/l in paddy field.The ramp of nitrogen-phosphorus loss was varied to intensity of rainfall, sometime to 5-6 times. For nitrogen nutrient, the ammonia was the main loss form to both paddy field and arid land, and for the former, the loss rate to 42.8 %, and for the latter, to 37.5 %. The total amount of nitrogen-phosphorus loss for arid land was higher than that for paddy field. Although the concentration of nitrogen-phosphorus was fluctuated with rainfall, the overall level was tend to downward. And the concentration of nitrogen-phosphorus at the beginning of the rainfall was higher than that at the end.Laboratory soil column leaching experimental results were consistent with field monitoring, and it showed that the nitrogen-phosphorus leaching in arid land was beyond that in paddy field. Under different fertilizer, nitrogen and phosphorus fertilizer ratio of total were quite different. In the paddy field washing, the conventional fertilization conditions, the proportion of nitrogen loss was in the range of 3.78-5.20%, total N loss ranged of 4.70-8.31%, and total phosphorus loss of 0.13-0.55%. In the fertilization condition, the loss ratio was in the 1.82-5.77% for nitrogen, in the 0.13-0.55% for total N, and in 0.44-0.56% for total phosphorus. In arid land washing, the conventional fertilization conditions, the proportion of ammonia loss was ranged from 6.51 to 10.16%, total N loss ratio range of 7.14-9.43%, total phosphorus in the range of 0.32-1.19% loss ratio. Fertilization conditions, the loss ratio in the 6.63-7.66% nitrogen, total N loss ratio range of 6.48-8.75%, and total phosphorus in the range of 1.20-3.18% loss ratio.