Abstract: 【Objective】The objective of this study is to explore the characteristics of nitrogen (N) flow of crop-livestock systems and its environmental effects on farming-pastoral transition zone in northwestern Shanxi Province, further to give scientific suggestions on the nutrient management and to speed up the adjustment progress of industrial structure in farming-pastoral transition zone in Shanxi Province.【Method】a systematic and quantitative analysis on the nutrient balance, nutrient losses of crop-livestock production in farming-pastoral transition zone (42 counties in total, mainly involving Datong, Shuozhou, Xinzhou, Lüliang, Linfen and Taiyuan) in Shanxi Province was reported using a coupled NUFER model (nutrient flows in food chains, environment and resources use) with GIS after collecting and sorting of data from statistical yearbooks data, literature, and field investigation.【Result】 In different counties, the N fertilizer application showed a great disparity, ranging from 6.7 to 253 kg·hm^-2, which means a 38 times difference between the maxima and the minima. The N input structure of different counties also varied, due to the different N application habits and cropping systems. Crop N uptake ranged from 19.11 to 96.75 kg·hm^-2, and the high amounts of crop N uptake were found in North and South regions, and low values in the middle regions. Crop N surplus ranged from -16 to 202 kg·hm^-2, showing a coexistence of N sufficient and N surplus. There was a great difference in external N input by feed in livestock production system in the zone. In Shanyin county of Shuozhou City, the external N input by feed reached up to 9 400 t, whereas in Wuzhai of Xinzhou City and Xixian, Daning and Puxian of Linfen City, the demand of feed by livestock production system was met by local cropping system. This shows a great variation in the livestock production scale and farming-pastoral industrial structure among those counties. N uptake of animal main product per unit area of farming land was 1.51-27.50 kg·hm^-2, with a range of 25.99 kg·hm^-2, indicating a great disparity in the livestock productivity level among different counties. In the northern counties of Shanyin, Huairen and Datong, N uptake of animal main products was ＞13 kg·hm^-2, showing a high N use efficiency of livestock production system in these counties. In the northern regions, the N load by manure was high (＞50 kg·hm^-2). There was an obvious spatial trend of N loss in crop-livestock production system. Grade I area (＞200 kg·hm^-2) was found in the north of the zone, Grade II area (120-200 kg·hm^-2) was found in the north and south of the zone, and Grade III area (＜120 kg·hm^-2) mainly distributed in the middle of the zone. Therefore, N loss and environmental issues occur in the crop-livestock production process in the northern part of the zone should be paid close attention in the future. 【Conclusion】 Unreasonable agricultural production structure and the segregation of agricultural and animal husbandry systems were the main reasons for the low N use efficiency in the farming-pastoral transition zone in northwestern Shanxi Province. In the future management of farmland nutrient resources, apart from rational spatial allocation of N resources, not only N input by both chemical fertilizers and livestock excrement/urine should be taken into account, but also N input from the environment. Also, the coupling of farmland production system and animal husbandry production system should be emphasized. By these means the production of crop and animal products at the minimum environmental costs can be achieved.

Key words: farming-pastoral transition zone, NUFER model, crop-livestock production system, nitrogen flow, environmental effects, Shanxi Province