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中国畜禽粪尿资源化利用潜力与土地承载力评估

Evaluation of the resource utilization potential and land carrying capacity of manure and urine of livestock and poultry in China

  • 摘要: 针对中国畜禽粪尿资源化利用潜力不明与土地承载力区域失衡问题,该研究在系统估算2022年中国生猪、奶牛、羊等11种畜禽粪尿及氮磷养分总量的基础上,构建“氮磷养分供需–耕地负荷预警”双维度评估框架,建立氮磷养分供需比评估体系。同时聚焦生猪、奶牛、肉牛、羊、蛋鸡、肉鸡6种传统优势畜禽,依据猪粪当量转换标准,开展耕地负荷与预警值评估。结果表明:2022年全国畜禽粪尿及氮磷养分产生量分别为16.25亿t、954.09万t和202.31万t,区域分布高度集中,其中内蒙古、四川、云南、山东、新疆等5省贡献了畜禽粪尿总量的33.78%。北京、上海因畜禽粪尿产生量最低,氮磷养分供需比仅为0.34和0.31,耕地污染负荷(氮负荷低于100 kg/hm2)显著低于全国均值(206 kg/hm2),呈现“低排放–低需求”的资源利用特征。全国氮磷供需比均值为0.53和0.54,理论承载空间剩余46.39%,但区域分异显著。青藏高原畜禽养殖结构以牛羊为主导,其数量在核算的11种主要畜禽中占比分别高达88.90%(西藏)和88.60%(青海),叠加高寒环境与散养模式导致西藏氮供需比高达18.85,单位耕地猪粪当量负荷预警值达Ⅵ级。东南沿海生猪密集区(存栏量占全国7.30%)因人均耕地低于0.02 hm2,单位耕地氮负荷(超过400 kg/hm2)远超欧盟临界值,预警值达Ⅴ级。研究实现中国11种畜禽氮磷养分测算与6类优势畜禽精准耕地负荷评估的参数协同,并提出差异化治理策略。该研究为中国种养循环规划及农业面源污染防治提供了“全口径测算–优势畜禽聚焦–区域适配治理”的科学方案。

     

    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/hm2, 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 hm2), 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.

     

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