Nitrogen Dynamics Simulation Of Watershed In The Three Gorges Reservoir Based On DNDC Model

Three Gorges water conservancy project is has attracted worldwide attention. Began filling with water from the Three Gorges Project reservoir built, Local eutrophication began to frequent, even Algal bloom. For the reservoir area caused serious ecological threat. Therefore, this article Taking Wangjiagou Three Gorges Reservoir watershed as a simple, based on DNDC model to simulate the characteristics of dynamics of soil nitrogen, to analysis the relevance between soil and surface water and analysis mechanism of soil nutrients loss, so as to provide theoretical basis for sustainable development of agriculture, ecological environment, reduce non-point source pollution in Three Gorges reservoir area. The main research conclusions are as follows:1) Model of DNDC simulated the dynamics of soil ammonium nitrogen, nitrate nitrogen in Wangjiagou Watershed, the simulated and measured values were significantly correlated.and relevant coefficient above 0.9, indicating that the model well captures the soil nitrogen Wangjiagou Watershed information on the dynamics and temperature, yield information. Therefore, the model has had the ability of small watershed soil nitrogen dynamics simulation2) soil ammonium nitrate content is gradually reduced over time in Small Three Gorges Reservoir watershed, and the two peaks appear within a year, the second peak is larger than the first peak. This is because the second planting season as mustard, compared with the first phase of the maize crops, fertilizing the soil is large. Therefore, resulting in higher peak of nitrogen in soil.nitrogen content of the soil profile for the same land use patterns reduced with increasing soil depth gradually.3) soil for Nitrogen gas and ammonia exhaust from spring to late summer over. Nitric oxide and nitrogen dioxide emissions concentrated in the summer and autumn season. Nitrogen gas emissions rangs from different types of land use. For emissions of nitrogen oxides expressed as forest land> paddy field> Dryland> parkland. Nitric oxide emissions performance dry land> paddy field> forest land> parkland. Nitrogen and ammonia, the highest is paddy field, dry land, parkland, forest land second.4) soil nitrate nitrogen leaching mainly based. This is because the soil in the presence of ammonium nitrate and ammonium nitrogen with a positive charge, easy to soil adsorption, it is not easy with the rainfall loss. The results showed that nitrogen leaching within a year after the first and then decreased, with the precipitation and changes. Under different land use patterns, soil nitrogen leaching content is inconsistent, expressed as dry land> parkland> forest land> paddy field5) The changes of nitrate and ammonia nitrogen in soil and surface water is consistent. The concentration of ammonia nitrogen in surface water and soil is significantly correlated (P<0.05), while the correlation between the concentration of nitrate nitrogen is not significant.6) soil nitrogen income under various land use patterns is not balanced. For the entire watershed, in addition to garden plot, the other land use types of nitrogen are in surplus. Input of N in farmland fertilizer, straw, atmospheric deposition, biological nitrogen fixation contribution of nitrogen inputs was 78.3%,16.25%,2.79%,2.53%, expressed as fertilizer>straw> Atmospheric Deposition>Biological Nitrogen Fixation. Fertilizer is the largest nutrient factor income. Output of Nitrogen in farmland harvest, denitrification, nitrogen runoff contribution expenditure was 54.67%, 29.78%,15.56%,expressed as crop uptake> denitrification>runoff. Crop uptake of nutrients is the biggest factor income. Wangjiagou Basin Farmland nitrogen imbalance, there has been a surplus. Different cropping systems, soil fertilizer revenue performance vegetable>ora>rice, fertilize of vegetable in all three systems accounted for 66.2%, corn is 28.5%, rice is 5.3%. Expressed as corn straw>vegetable>Rice. Atmospheric deposition, biological nitrogen fixation and pesticides impact the performance of the three systems is vegetable>corn>rice, but three of the contribution of the three systems was 4.97%, less than 5%, so little effect on the system, nitrogen content of harvested crops in Three systems showed vegetable>corn>rice harvest,for each system contribution rate of 10.7%, 34.0%,55.3%, However, the utilization of fertiliz in the three systems expressed that rice is 72.8%,corn is 36.1%, vegetable is 27.9% Denitrification showed vegetable>corn>Rice. In Runoff output the rice, corn, vegetable contribution rate were respectively 80.6%,80.6%,19.4,showed as corn=rice>vegetable. Different cropping systems nitrogen is inbalances and have emerged surplus.Nitrogen revenue, expenditure, and surplus of vegetable system is the largest, followed by corn, rice is minimum.