基于NUFER模型的生猪养殖氮磷利用效率及排放时空变化

Use efficiency and emission spatial-temporal variability of nitrogen and phosphorus for pig production in Beijing

城市郊区集约化畜禽生产系统的快速发展在满足日益增长的畜产品需求的同时也带来了严重的环境问题。该研究利用北京生猪养殖场调研数据和养分流动模型NUFER分析了1980年到2013年北京城郊生猪生产体系氮、磷养分利用效率和环境损失时空变化,并利用情景分析提出了5种饲料和粪尿优化管理措施。从1980年到2013年,育肥猪个体尺度(仅包括育肥猪)氮利用效率从17.8%增加到19.0%,磷利用效率从32.0%增加到35.8%;群体尺度(包括育肥猪、母猪等)氮利用效率从16.0%增加到16.7%,磷利用效率从29.5%降低到23.4%;系统尺度(土壤-饲料-生猪)氮利用效率从18.5%降低到11.4%,磷利用效率从41.6%降低到17.1%。2013年,总氮损失和总磷损失分别为4.22和0.65万t,较1980年分别增加了56.9%和97.0%。产生这一变化的原因是生猪养殖模式从家庭和传统养殖模式向集约化模式转变,家庭副产品作为饲料利用的比例迅速降低,养分循环链条中断,从而导致系统养分利用效率不断降低。但就育肥猪个体尺度和群体尺度而言,集约化生产模式优化了饲料精准喂养和粪尿管理。与此同时,2000年后国家提出了大量有关畜禽养殖的政策、法规、标准和规范,使得1980年至2013年间养分利用效率出现先减后增和环境损失出现先增后减的趋势。空间分布变化结果显示,北京城区和近郊区域由生猪养殖导致的环境损失迅速减少,而远郊区域的环境损失快速增加,这主要归因于城市发展规划。

To meet the growing demand of livestock products, the rapid development of intensive livestock production system in peri-urban area has brought many serious environmental problems. However, little is known about the quantitative information of livestock production in peri-urban environments. In this study, we analyzed the nitrogen and phosphorus use efficiency and losses and the temporal-spatial variation of pig breeding, using the data of a comprehensive survey conducted on 92 pig farms during 2012-2013 and calculated with the NUFER-animal model （nutrient flows in food chains, environment and resources-animal model）. The NUFER model is a deterministic model with large databases that calculates the flows, use efficiencies, and emissions of N and P in the food chains in 31 regions of China and the national level on an annual basis. It uses a mass balance approach with detailed amount of the partitioning of nitrogen and phosphorus inputs and outputs. Then, 5 kinds of feed and manure management optimization measures were proposed using scenario analysis. From 1980 to 2013, the nitrogen use efficiency at the fattening level （fattening pigs only） increased from 17.8% to 19.0%, and the phosphorus use efficiency increased from 32.0% to 35.8%; the nitrogen use efficiency at the herd level （fattening pigs plus sows and boars） increased from 16.0% to 16.7%, and the phosphorus use efficiency decreased from 29.5% to 23.4%; the nitrogen use efficiency at the system level （soil-feed-pig breeding system） decreased from 18.5% to 11.4%, and the phosphorus use efficiency decreased from 41.6% to 17.1%. In 2013, the total nitrogen and phosphorus losses were 4.2×10^4 and 0.65×10^4 t, respectively, increasing by 56.9% and 97.0% comparing with that in 1980. The reason for this change was that the breeding mode of pig breeding changed from family and traditional mode to intensive mode. For the proportion of the feed utilization, the family was rapidly decreased, which led to the efficiency decreasing at system scale. However, due to the precision feeding and manure management, the nutrient use efficiency was increased at animal and herd level. At the same time, the government proposed many policies, laws and regulations, standards and norms since 2000, so that the nutrient use efficiency first decreased and then increased and the environmental losses first increased and then decreased from 1980 to 2013. The result also showed that the proportion of different feed sources of pig breeding in peril-urban area changed a lot in 2013. Feed gradually shifted from local production to import from abroad, and feed input conversed from the by-product feed to the main product feed. The results of spatial distribution variation showed that the environmental losses were rapidly decreased at urban and suburban area, and rapidly increased at outer suburb of Beijing. These spatial- temporal changes were mainly attributed to the urbanization and the urban development planning. Insights from pig breeding systems in peri＇urban region of Beijing provide relevant guidance to the sustainable livestock production in cities of rapidly developing countries.