Distribution of manure-derived nitrogen and phosphorus from intensive livestock farming and their recycling potential

To promote the rational utilization of manure nutrient resources and provide a reference for environmental protection policies, it is imperative to analyze the spatial distribution characteristics of nitrogen (N) and phosphorus (P) discharged from the manure waste of intensive livestock and poultry farms, as well as quantitatively assess the recycling capacity of manure nutrients by farmland. In this study, the spatial data of 1576 intensive livestock and poultry farms in the area under the administration of Shuozhou City, Shanxi Province, were collected. NUFER (NUtrient flows in Food chain, Environment and Resources use) animal model was employed to estimate N and P production from livestock and poultry manure of these farms. The spatial distribution characteristics of manure nutrients were analyzed, and the main hotspots of manure-derived N and P production were delineated using GIS. The recycling levels and radius of manure-derived N and P in farmlands were calculated using remote sensing and GIS spatial analysis methods, and the recycling potential of manure-derived N and P in each district and county was evaluated. The production of manure-derived N and P production was high in the east and low in the west in Shuozhou City, predominantly in the three eastern districts/counties, where 15.46 Gg of N and 2.16 Gg of P were produced, accounting for 80.93% and 82.16% of the total production, respectively. Farmland in this area had great potential for recycling manure-derived N and P. According to the principle of “recycling in the neighborhood”, 9.94×10⁴ hm² of farmland was required for the recycling of the total manure-derived N, which constitutes 25.44% of Shuozhou’s total farmland. Regarding manure-derived P, only 4.69×10⁴ hm² of farmland was needed for its recycling, accounting for 12.00% of Shuozhou’s total farmland. The farmland with a full load of manure-derived N and P was mainly distributed in Huairen City, Yingxian County, and Shanyin County in the eastern part of Shuozhou, encompassing 8.21×10⁴ hm² and 3.93×10⁴ hm² in area and accounting for 82.69% of the total N production and 83.92% of the total P production, respectively. The majority of the manure-derived N and P in Shuozhou area can be consumed within a radius of 3 km. Based on the relationships between the scale and spatial distribution of livestock and poultry farms and the spatial location of farmland, this study developed a method to evaluate the recycling level of livestock and poultry manure for quantifying and assessing the recycling capability of manure-derived N and P from intensive livestock and poultry farms. These findings provide a scientific basis for the spatial arrangement optimization of livestock farms and the evaluation of relevant environmental policies in the future.