Input-output Budgets For N And P In A Typical Purple Soil Sloping Ploughland In Three Gorges Areas

Three Gorges Reservoir,with a storage capacity of 39,300,000,000 m3 ,is the biggest artificial lake in the world and is also an important strategy of chain’s fresh water resources.It is significant to protect water resources of reservoir.With the running of Three Gorges Project, the treat, from agricultural non-point source pollution of N and P to the environment of the reservoir water, becomes increasingly remarkable. However, present study on the storehouse district agricultural non-point source pollution of N and P is still on the qualitative investigation stage of pollution way and the quantitative investigation still is not perfect.For insufficient understanding of the source of pollution. It is serious influence the deal with agricultural non-point source pollution of N and P in Three Gorges Reservoir areas.So estimation of input-output budgets of N and P becomes the key link to research and deal with the agricultural non-point source pollution of N and P in Three Gorges Reservoir areas.At present, the methodology of research on input-output budgets of N and P, which based on the big river basin scale and treated the soil as the research object, inadequately considers the migration process of input-output of N and P in river basin. Therefore, this paper puts forward a way that is to study input-output budgets of N and P in the Xinzheng watershed in Zhongxian county, Chongqing, which is a typical purple soil sloping ploughland in the Three Gorges areas. The relevant research work is as follows:①In this research, based on the soil model for general model and the characteristics of migration of N and P on the watershed space, we construct the watershed model of input-output budgets of N and P. The model consists of exogenous input、recycle and exportation of N and P. In the three part, the recycling module is the biggest difference between soil model of input-output budgets of N and P and watershed modelf input-output budgets of N and P. N and P balance calculation, considering not only the recycling of N and P for small watershed input the effects of N and P, also considered the recycling N and P output for small watershed in the effects of N and P. N and P recycling module joined the small watershed N and P transfer equilibrium process characteristic analysis and non-point source N and P generation mechanism research foundation.②To the based on soil model of input-output budgets of N and P, we determine ways of exogenous input and exportation of N and P : fertilizers N and P, atmospheric N and P, the biological N fixation, waste of N and P, returning the straw returned to sell of N and P, leaching N and P, runoff N and P, soil erosion N and P, ammonia volatile N, denitrifying N. Biological nitrogen fixation include the symbiotic nitrogen-fixing and non-symbiosis nitrogen-fixing way. According to the space migration characteristics of N and P, we increased the recycle module of N and P in the watershed and convent the recycling way of N and P in the watershed: sales N and P, organic fertilizer N and P, seeds N and P, straw fuel N and P, organic waste N and P and so on. According to the special attributes of the purple soil parent rock weathering input of N and P, we add the purple soil parent rock weathering input of N and P into the model of input-output budgets of N and P.③According to the logical analysis of input-output budgets of N and P in a typical purple soil sloping ploughland watershed, the model parameters is divided into basic data and characteristic parameters. For in situ observation of small watershed, we obtain characteristic parameters such as the atmospheric settlement of nitrogen and phosphorus, leaching of nitrogen and phosphorus, runoff nitrogen phosphorus, ammonia nitrogen and phosphorus volatile, soil nitrogen phosphorus. Two times of small watershed enter a census, obtain the fertilizer varieties and dosage, food feed types and consumption, nitrogen fixation crop types and planting area, permanent population, livestock types and quantities and other basic data; 9 of small watershed of sample and 10 farmers tracking observation, we obtain the characteristic parameters such as the nitrogen and phosphorus fertilizer coefficient, aspertate than, straw uses and usage, seeds, organic waste production rate of stalks; Access for three gorges reservoir area and the related purple soils, obtain characteristic parameters such as the biological nitrogen fixation, soil weathering of nitrogen and phosphorus, straw and seeds of nitrogen and phosphorus content, people of nitrogen and phosphorus, livestock waste discharge amount of nitrogen and phosphorus content, and organic waste nitrogen phosphorus content, denitrifying. We calculat 21 the way of input-output budgets of N and 18 the way of input-output budgets of P in a typical purple soil sloping ploughland watershed in Three Gorges areas.④Lossing risk of N and P present in a purple soil sloping ploughland watershed in Three Gorges areas, lossing N and P are 294.78 kg/（hm₂·a） and 12.81 kg/（hm₂·a）. leaching, runoff, soil erosion is agricultural non-point sources of nitrogen and phosphorus pollution in a typical purple soil sloping ploughland watershed in Three Gorges areas. In addition, 66.20% of the loss by denitrification, ammonia nitrogen gas volatile ways such as volatile loss.⑤Surplus quantity of N and P in a typical purple soil sloping ploughland watershed in Three Gorges areas cultivated land are 274.14 kg/（hm₂·a）and 48.20 kg/（hm₂·a）. The N surplus is N pollution potential critical value 180 kg/（hm₂·a） of 1.52 times, higher than the national average 154 kg/（hm₂·a）.The P surplus higher than the national average 26.1 kg/（hm₂·a）. The non-point source potential pollution of N and P present in a typical purple soil sloping ploughland watershed in Three Gorges areas.⑥Fertilizer N and P quantity of cultivated land for 516.80 kg/（hm₂·a） and 60.16 kg/（hm₂·a） in a typical purple soil sloping ploughland watershed in Three Gorges areas, more than 250 kg/（hm₂·a） and 35 kg/（hm₂·a） loss risk value. The dry land waste of N and P content is 400.10 kg/（hm₂·a） and 42.25 kg/（hm₂·a）, more than 170 kg/（hm₂·a） and 35 kg/（hm₂·a） loss risk value. The main reasons are fertilizer and waste of N and P in three gorges reservoir area is excessive input purple soil agricultural non-point cultivated land of nitrogen and phosphorus pollution. In addition, the purple soil slope cultivated land utilization of nitrogen and phosphorus recycling is only 42.34% and 76.35%.The main reason is recycling of nitrogen and phosphorus utilization rate is low also resulted in three gorges reservoir area purple soil agricultural cultivated land non-point source of nitrogen and phosphorus pollution.⑦Biological fixation N, rock weathering N and P are 33.31 kg/（hm₂·a）, 0.8 kg/（hm₂·a） and 0.5 kg/（hm₂·a） in a typical purple soil sloping ploughland watershed in Three Gorges areas.