Abstract: The Huang-Huai-Hai region is an important cropping and pig breeding base in China. It is of great significance to study the carrying capacity of pigs for guiding pig breeding planning and returning of pig manure to field. In this paper, the pollutants yield of pig breeding and the load of cultivated land in Huang-Huai-Hai region was estimated. Based on the concept of "The amount of breeding is determined by the amount of cultivation and demand", the whole Huang-Huai-Hai region was taken as the research scope and the most common 6 crops in the area were taken as the research objects to study the carrying capacity of different crops for pig breeding. The results show that, the total output was 180.712 5 million of pigs in 2017 in the region and the annual yield of pig manure, wastewater, TN, TP, Cu and Zn were 38 868 400, 287 694 300, 964 400, 136 200, 5 799 and 8 805 tons, respectively, and the carrying capacity of cultivated land for pig breeding was 6.22-11.33 pigs equivalent·hm^-2. For the six crops studied, their carrying capacity of pigs in the region was 1.58-20.96 pigs equivalent·hm^-2 and crop species and area were the important influencing factors. Overall, the carrying capacity of different crop land for pig breeding in the region was in the order of wheat > rice > cotton ≈ corn > rape > soybean. The land carrying capacity of rice, wheat, rape, corn, soybean and cotton farmlands in the region for pig breeding were 10.32, 11.47, 4.72, 5.39, 3.77 and 5.53 pigs equivalent·hm^-2, respectively. In summary, factors such as crop species, crop yield, soil fertility and replacement ratio of manure in the field should be taken into consideration when evaluating the amount of manure returned from pig breeding and the farmland support of pig farms.

Key words: Huang-Huai-Hai region, crop species, land carrying capacity, nitrogen, phosphorus, pig manure