泛种养结合视角下北京市养殖业土地承载力评估

种养结合是中国未来农业绿色发展的重要方向。其中，对畜禽粪污的土地承载力的准确估算是关键。针对北京市畜禽粪污消纳的土地没有充分利用及其氮磷需求取值不够准确的问题，该研究根据畜禽养殖数据计算了2018年北京畜禽养殖粪污产生量和氮磷养分资源量，以粮地、菜地、园地、部分林地、草地及未利用土地6种地类作为畜禽粪污的消纳场所，利用统计年鉴和ArcGIS估算了6种类型的土地资源量，根据文献综合分析了各地类单位面积的氮磷养分需求量，进而计算了北京市域内畜禽养殖业的土地承载力。结果表明：2018年北京市畜禽养殖总量为453万头猪当量，畜禽粪污产生总量为380.1万t，氮磷养分资源量分别为2.61万及0.53万t。在有机肥全部替代化肥的情况下，仅以耕地（粮地、菜地）作为畜禽粪污的消纳场所，则全市种植业土地能够承载的最大养殖量为675万头猪当量；若以6种土地类型作为畜禽粪污的消纳场所，则为1 089万头猪当量，是仅以耕地作为消纳场所的1.61倍。若有机肥50%替代化肥，仅以耕地为畜禽粪污消纳场所，土地承载力为337.6万头猪当量，则2018年的养殖规模已经超过耕地承载力。若以6种土地作为消纳场所，其土地承载力为544.5万头猪当量，与现养殖规模相比还有20.1%的养殖潜力。因此，在环境保护的前提下促进养殖业的发展，一是要扩大有机肥对化肥的替代比例，二是要将更多的可作为畜禽粪污消纳的土地类型加以充分利用。

Assessment of land carrying capacity of animal production in Beijing from a wider perspective of combination of planting and animal breeding

A strong market demand is ever increasing for animal protein in China. Correspondingly, this increase inevitably requires the expansion of animal farming industry. However, a trade-off is also highly necessary between the livestock/poultry manure and environmental pollution. Arable land can serve as a disposal site of animal manure in some regions. Furthermore, an optimal combination of planting and animal breeding is also critical to achieve the win-win goals of environmental protection and aquaculture development. Therefore, it is very necessary to accurately estimate the land carrying capacity for animal manure in modern agriculture. In this study, a systematic evaluation was made on the amount of manure production and nitrogen, phosphorus nutrient resources within the animal wastes in 2018 using the livestock and poultry breeding data in Beijing Statistical Yearbook. Six types of land were taken as the sites for the consumption of livestock and poultry manure, including grain field, vegetable field, orchard, available woodland, available grassland, and unused land, compared with only arable land was considered in the previous studies. Both Statistical Yearbook and ArcGIS were used to estimate the above-mentioned land resources. The nitrogen and phosphorus nutrient demand per unit area in the various land types were analyzed comprehensively, thereby to calculate the land carrying capacity of animal breeding industry in the study area. The results showed that the total amount of livestock and poultry manure was 3.801 million tons in Beijing in 2018, where the nitrogen and phosphorus nutrient resources were 26 100 and 5 300 t, respectively. In terms of nitrogen and phosphorus, the total amount of animal breeding was equivalent to 4.53 million and 5.13 million pig equivalents, respectively. Nevertheless, nitrogen was the significant limiting factor of pollution from the perspective of environmental protection. The total areas was about 218 400 hm2 available for the animal manure accommodation land in the six types of land. Among them, a major of arable land, the grain and vegetable field reached 126 000 hm2, accounting for 52% of the total area of land. The available area of orchard field, woodland, grassland, and unused land were 59 000, 37 600, 9 171, and 79.6 hm2, respectively. The nutrient requirement value of nitrogen and phosphorus per unit area were 308.9 and 72.9 kg/hm2 for the grain field; 404.2 and 122.9 kg/hm2 for the vegetable field; and 250 and 55 kg/hm2 for the orchard field. Assuming that the plant nutrients were supplied only by organic fertilizer from animal manure, the maximum land carrying capacity for animal breeding was 6 752 100 pigs equivalent, if only arable land (including grain and vegetable field) were used as the accommodation sites for livestock and poultry manure. If the six types of land were all used concurrently for the consumption of animal manure, the maximum land carrying capacity for animal breeding increased to the equivalent of 10.89 million pigs, 1.61 times of that of arable land. Assuming that the plant nutrients were provided 50% by organic and 50% by chemical fertilizers, the maximum land carrying capacity for animal breeding was reduced to the equivalent of 3.376 million pigs equivalent, if only arable land was used as the accommodation field of livestock and poultry manure. In this case, the breeding scale exceeded the carrying capacity of arable land in 2018, where it may cause environmental pollution. Fortunately, the land carrying capacity was 5.45 million pigs equivalent for the six kinds of land concurrently, 20.1% more breeding potential, compared with the actual breeding amount in 2018. Therefore, it is necessary to increase the replacement ratio of organic fertilizer to chemical fertilizer during this time, thereby to fully utilize the multiple types of land to absorb livestock and poultry manure. The finding can provide insightful ideas for the long-term coordinated development of environmental protection and animal breeding industry.