Abstract: 【Objective】 Crop-livestock production structure and their integration rate has been changed greatly in China since the reform and opening policy. These changes have large impacts on the nutrient flows and environmental losses in the crop-livestock production chain. Here, Luancheng district of Hebei province was used as an example to analyze the temporal and spatial changes of crop-livestock production structure and impacts on nutrient flows and losses from 1985 to 2014, and to determine the key impacting factor of nutrient losses in crop-livestock system. These results can be used to improve the understanding of sustainable agriculture not only for Luancheng district, but also for other counties which faced the same situation with Luancheng district. 【Method】 the nutrient flows in Luancheng district were analyzed by using NUFER (nutrient flow in the food system, environment and resource) model and field survey. The NUFER model calculated nitrogen (N) and phosphorus (P) flow, use efficiency and environmental losses of crop production system, livestock system, food processing system and household consumption system. Field surveys were conducted through the face-to-face questionnaires to collect information about the nutrient management. The contents of the questionnaires include the production practices and nutrient input-output of crop system, livestock feeding management and manure management practices, manure recycle to crop land and nutrient input-output of the livestock system. 【Result】 In 2014, the percentage of vegetable and fruit sown area to the total sown area was 25%, N and P inputs of agricultural land were 763 kg N·hm^-2 and 335 kg P·hm^-2, the average surplus of N and P were 132 kg N·hm^-2 and 237 kg P·hm^-2 agricultural land, the livestock density reached up to 18 LU/hm² agricultural land, feed import rate reached to 75%, input of external N and P from livestock production accounted for 57% and 39% of the total external input in crop-livestock system, and output of N and P as main animal products accounted for 60% and 33% of the output in crop-livestock system. All of these indicators indicated that Luancheng district was a typical high environmental loads peri-urban production system. From 1985 to 2014, manure N recycled rate decreased from 59% to 35%. Meanwhile, the nitrogen use efficiency (NUE) decreased from 45% to 43%, and the phosphorus use efficiency (PUE) decreased from 32% to 23% in the crop production during the same period. However, different with that of crop production, the NUE in animal production was increased from 14% to 30%, and the PUE of animal production was increased from 4.4% to 10%. For the whole crop-livestock production system, the NUE decreased from 41% to 36%, and the PUE decreased from 27% to 16%, respectively. In 2014, when 1 kg N was delivered into the crop products, 0.66 kg N lost to environment. Similarly, when 1 kg P was delivered into the crop products, 0.11 kg P lost to environment. The average N and P losses were 1.4 kg N and 1.8 kg P when 1 kg of N and P was retained in animal body, respectively. At the crop-livestock production level, the average N and P losses was 1.5 kg N·kg^-1 and 0.75 kg P·kg^-1. Ammonia was the major N loss pathway both in crop and livestock production, however, manure direct discharge was the main P loss pathway in the crop-livestock production system.【Conclusion】Driven by the urbanization and structure changes of crop-livestock system, the crop-livestock system in Luancheng district has been defined as the high input, high yield, low nutrient use efficiency, livestock dominated, high environmental risk typical and high environmental loads peri-urban production system during the past 30 years. The low nutrient use efficiency and high nutrient losses were due to the high livestock density, decoupled crop-livestock production and irrational nutrient management practices. Therefore, it is important to determine the reasonable livestock production capacity and improve the feed management and implement the whole chain manure management practices to achieve the sustainable crop-livestock production in Luancheng district.

Key words: nitrogen, phosphorus, crop-livestock system, nutrient use efficiency, NUFER model