Abstract:
Here, a systematic evaluation was performed on the resource utilization potential and land carrying capacity of the manure and urine from the livestock and poultry in China. Regional disparities were also considered to develop the inventories of the manure, urine, nitrogen (N), and phosphorus (P) production for 2022. Furthermore, six major animal species were selected, including the swine, dairy cattle, beef cattle, sheep, goat, layer, and broiler, thereby representing the most significant contributors to agricultural nutrient flows. A dual-dimensional framework was established to integrate the nutrient supply-demand balance with the cropland load warning. The Nitrogen and Phosphorus Supply-Demand Ratio (NPSDR) was utilized to quantify the relationship between the manure-derived nutrients and crop requirements. The nutrient utilization capacity was accurately assessed, according to the statistical analysis of the regional crop patterns, soil characteristics, and climate conditions. The cropland carrying capacity was normalized for the nutrient contents over different manure types after the standardized Pig Manure Equivalent (PME) conversion. The conversion coefficients were derived from the extensive laboratory analysis of the nutrient composition in various manure types. Results demonstrated that there were the national production volumes of 1.625 billion tons for the manure and urine, 9.54 million tons for N, and 2.02 million tons for P. Five provinces—Inner Mongolia, Sichuan, Yunnan, Shandong, and Xinjiang—collectively contributed 33.78% of the total manure and urine. The spatial distribution patterns were highly concentrated to reflect the regional specialization in animal production. Metropolitan areas, including Beijing and Shanghai, showed the lowest quantities of manure generation, with the extreme differences exceeding 80-fold, compared with the high-production regions. The NPSDR values were only 0.34 and 0.31, respectively. The cropland N loads were below 100 kg/hm
2, significantly lower than the national average of 206 kg ha
-1. The "low-emission, low-demand" resource utilization was distributed in the highly urbanized regions with limited agricultural activity. The national average NPSDR values for the N and P were 0.53 and 0.54, respectively. The approximately 46.39% was remained on the theoretical carrying capacity. The substantial regional heterogeneity was observed over the different agro-ecological zones. Among them, the Qinghai-Tibet Plateau (Qinghai and Tibet) shared the extreme N supply-demand ratio of 18.85 in Tibet, due to the substantial yak and Tibetan sheep inventories combined with the high-altitude environmental constraints and extensive grazing systems. The PME load per unit cropland reached the Level VI warning. The highest alert category indicated the severe environmental risk. Whereas, the excessive N loading rates were observed over 400 kg ha-1 in the intensive livestock production zones along the southeastern coastal region, with the 7.30% of the national swine inventory. Level V warnings were then triggered due to severely limited per capita cropland availability (<0.02 hm
2), thus exceeding European Union critical thresholds. The critical challenge was also highlighted in the nutrient management in the high-density livestock production areas. The parameters were developed to synchronically estimate the nutrient contents of the multiple animal categories. While the cropland load was precisely assessed for the spatially differentiated strategies, according to an integrated framework of the national accounting. The key livestock sources were regionally adapted to support the national planning and effective pollution control of sustainable agriculture in China. The findings can provide valuable insights for decision-making on sustainable livestock production in developing countries, particularly for agricultural nutrient management and environmental protection.