Regional Rural Development, Nitrogen Input and Output in Farming-Grazing System and its Environmental Impacts—A Case Study of the Wuliangsuhai Catchment

The nitrogen flow in the agricultural production activities has become one of the most important factors affecting the human environment, especially regional aquatic environment. This paper analyzes the input and output of nitrogen of farming-grazing system and its influences on the environment by using of the regional nitrogen flow model in the studied area of Wuliangsuhai catchment of Inner Mongolia Autonomous Region in 2006. The research results indicate that nitrogen input of Wuliangsuhai catchment mainly concentrates in arable land, very few in grassland. Nitrogen input is more than output in farming system, and the nitrogen surplus is 3.08×104 tons, averagely 65.1 kg/hm2. Nitrogen input is less than output in grassland system, and there is a nitrogen deficit of 7.01×103 tons, averagely 8.59 kg/hm2. The loss of massive nitrogen is a primary factor causing the local grassland degradation. In addition, the gross nitrogen exported into surface water by surface runoff every year has achieved 1.8×104 tons, which brings great pressures on the regional water environment. Most of lost nitrogen is to be deposited in rivers and lakes, less likely to return farming-grazing system. Fertilizer use on the arable land is the main source of nitrogen exported into surface water from regional farming-grazing system. Excessive application of nitrogen fertilizer in the arable land has led to accumulation of soil nitrogen and posed a great threat to the aquatic quality of Wuliangsuhai catchment, whereas the grassland is confronted with a severe nitrogen deficit which has resulted in widespread grass degradation. Therefore it may be an efficient way to mitigate the problems simultaneously by regulating and balancing the nitrogen flow between the farming system and the grazing system, and the control of agricultural non-point source pollution should be the priority strategy to management and improve the aquatic quality of Wuliangsuhai catchment.