[Livestock and Poultry Faeces Nitrogen Loading Rate and Its Potential Return to Farmland in China]

To clearly analyze livestock and poultry faeces and the nitrogen loading rate of farmland in different provinces of China and their potential return to agricultural land, the changes of the output of various livestock and poultry faeces in China and the proportion of faeces from all types of livestock and poultry since 1978 were estimated in this paper based on statistical data and literature reviews using the pig manure equivalent (based on nitrogen) and the spatial distribution and pollution risk of livestock and the poultry faeces and nitrogen loading rates. Furthermore, the nitrogen return potential from animal faeces to farmland was analyzed and evaluated for different provinces of China in 2016. The results show that the pig manure equivalent (N) and total N from livestock and poultry faeces in China increases from 1978 to 2005 and is stable from 2005 to 2016. By 2016, the pig manure equivalent (N) and N were 366822.01×10⁴ t and 2024.10×10⁴ t, respectively, reflecting an increase by 105.78%. Approximately 94.03% to 98.34% of the faeces was from poultry, sheep, pigs, and cattle. The livestock and poultry faeces pig manure equivalent (N) and nutrient N were mainly distributed in North-Central China, especially in the Henan Province, accounting for 22.25% and 8.81% of the total in China, respectively, followed by the Sichuan Province. Based on the arable land, planting, and farmland areas, the pig faeces equivalent (N) and its N nutrient per unit area were calculated and the environmental risks were evaluated based on r values. Based on the arable land area, the southwestern and southeastern regions have large loading rates, while the northcentral region has a serious pollution risk of grade Ⅳ. Based on the planting area, the northwestern and southwestern regions have relatively large loading rates, while the northwestern and northcentral regions have pollution risks of grade Ⅲ. Based on the farmland area, the northcentral and southeastern regions have great loading rates and the northcentral region has a pollution risk of grade Ⅲ, Hunan has the largest loading rate, and Beijing, Shandong, and Henan have grade Ⅳ pollution risks. The livestock and poultry faeces pig manure equivalent (N) and amount of N nutrients returning to farmland in China are 113480.75×10⁴ t and 626.15×10⁴ t, respectively, equivalent to 3.07 t·hm^-2 and 16.92 kg·hm^-2, respectively, and the northcentral region has the largest rates with 8.27 t·hm^-2 and 45.62 kg·hm^-2, respectively. Based on 50% of the environmental capacity of faeces N, that is, 85 kg·hm^-2, the N nutrient return can increase by 2520.21×10⁴ t. The Heilongjiang Province has the greatest potential return, followed by the Sichuan Province.