Eco-environmental Problems Of Farmland In Sichuan And Sustainable Development Of The Farmland Ecosystem In The Purple Hilly Area In Central Sichuan Basin

Farmland ecosystem is the material foundation of human being existence. The dynamic balance among crop, soil and fertilizer is the base of the health and sustaining development of the Farmland ecosystem. The unbalance of nutrient, soil and water loss are not only the essential eco-environmental problems within the farmland ecosystem, but also the root of most problems out of the system, especially the water pollution.The use of fertilizer in modern agriculture broke the close circle of nutrient in the traditional farmland ecosystem. At one hand the use of fertilizer improved the productivity of the farmland, and augmented the yield of the crop. In the other hand there appeared a series of problems in the farmland ecosystem because of the excessive and unbalanced fertilization. First, the excessive use of the fertilizer broke the dynamic nutrient balance, the unbalanced fertilization reduced the fertilizer efficiency of the corp. Second, a great deal of remained fertilizer which was not adopted by crops entered the water and atmosphere, it caused pollution and wasted the resources at the same time.Sichuan is a great province of China in agricultural manufacture, and the dosage of fertilization in per area preponderated the average level of our nation by 47.76%. In this paper the farmland nutrients balance was calculated. Along with the increased amount of fertilizer, the input of the nutrients was augmented, the N and P weresurplus, especially the N, the loss of the nutrients increased at the same time. Nowadays non-point pollution caused by N from farmland is more and more serious in Jialing river and Tuojiang river in Sichuan province. In Jialing river the concentration of N in flood season is higher than dry season, obviously it is caused by the N loss from farmland. Besides the pollution of surface water, the groundwater is polluted also, the situation is more serious in Shuangliu county.The purple hilly area is the principal agriculture part in Sichuan province, and at the same time water and soil loss is most serious in this area. Along with the water and soil loss, the nutrient in the farmland soil lost also. Take Nanchong as a typical example, Different approaches of the nutrient loss are calculated in the fifth chapter. Results show that the majority of nutrients, not only the N but also the P was removed with runoff and sediment in the purple hilly area in central Sichuan basin. Sediment is the main way that caused nutrient losing from farmland. The content of nutrients in the sediment was much higher than in the runoff, more than 85.67% of total N and 89.28% of total P is transported by sediment. The loss rate of N was composed of 22.9% of the nitrogenous fertilizer amount, and the of P is 41.4% . No doubt it is significant in terms of theory and practice to learn measures of protecting farmland, and to reduce the nutrient loss from farmland, so the sustainable development can be achieved in the purple hilly area in central Sichuan basin.