Rothwell S A, Doody D G, Johnston C, Forber K J, Cencic O, Rechberger H, Withers P J A
Lancaster Environment Centre, Lancaster University, Lancaster, UK.
Agri Food and Biosciences Institute, Belfast, Northern Ireland, UK.
Resour Conserv Recycl. 2020 Dec;163:105065. doi: 10.1016/j.resconrec.2020.105065.
Current use and management of phosphorus (P) in our food systems is considered unsustainable and considerable improvements in the efficiency of P use are required to mitigate the environmental impact of poor P stewardship. The inherent low P use efficiency of food production from animals means food systems dominated by livestock agriculture can pose unique challenges for improving P management. This paper presents the results of a substance flow analysis for P in the Northern Ireland (NI) food system for the year 2017 as a case study for examining P stewardship in a livestock dominated agricultural system. Imported livestock feed was by far the largest flow of P into the NI food system in 2017 (11,700 ± 1300 t) and P from livestock excreta the largest internal flow of P (20,400 ± 1900t). The P contained in livestock slurries and manures alone that were returned to agricultural land exceeded total crop and grass P requirement by 20% and were the largest contributor to an annual excess soil P accumulation of 8.5 ± 1.4 kg ha. This current livestock driven P surplus also limits the opportunities for P circularity and reuse from other sectors within the food system, e.g. wastewater biosolids and products from food processing waste. Management of livestock P demand (livestock numbers, feed P content) or technological advancements that facilitate the processing and subsequent export of slurries and manures are therefore needed.
目前我们食物系统中磷（P）的使用和管理被认为是不可持续的，需要大幅提高磷的使用效率，以减轻磷管理不善对环境造成的影响。动物食品生产中固有的低磷使用效率意味着，以畜牧业为主的食物系统在改善磷管理方面可能面临独特的挑战。本文介绍了2017年北爱尔兰（NI）食物系统中磷的物质流分析结果，作为研究以畜牧业为主的农业系统中磷管理的案例。2017年，进口牲畜饲料是流入NI食物系统的最大磷流（11700±1300吨），牲畜粪便中的磷是最大的内部磷流（20400±1900吨）。仅返回农田的牲畜粪便和粪肥中的磷就超过了作物和牧草总磷需求量20%，并且是土壤每年过量积累8.5±1.4千克/公顷磷的最大贡献者。当前由牲畜驱动的磷过剩也限制了食物系统内其他部门（如废水生物固体和食品加工废弃物产品）实现磷循环利用的机会。因此，需要对牲畜的磷需求（牲畜数量、饲料磷含量）进行管理，或者通过技术进步促进粪便和粪肥的处理及后续出口。
