NUTRIENT USE EFFICIENCY AND LOSSES OF INDUSTRIAL FARMS AND MIXED SMALLHOLDINGS:LESSONS FROM THE NORTH CHINA PLAIN

The proportion of industrial livestock in China has increased over the past 30 years,which increases animal performance but causes the decoupling of crop and livestock production.Here,we aimed to quantify nutrient flows,nutrient use efficiency,and nutrient losses in different livestock systems in the North China Plain based on the NUFER-farm model.Activity data were collected by face-to-face surveys on pig and dairy(41 livestock farms)during 2016-2018.The two systems included industrial farms and mixed smallholdings.In mixed smallholdings,4.0%and 9.6%of pig and dairy feed dry matter(DM)were derived from household farmland,but 4.8%and 9.3%of manure DM recycled to household farmland.Nutrient use efficiency in industrial farms was higher than in mixed smallholdings at animal level,herd level,and system level.To produce 1 kg N and P in animal products,nutrient losses in industrial pig farms(2.0 kg N and 1.3 kg P)were lower than in mixed pig smallholdings,nutrient losses in industrial dairy farms(2.7 kg N and 2.2 kg P)were slightly higher than in mixed dairy smallholdings.Liquid manure discharge in industrial farms was the main losses pathway in contrast to mixed smallholdings.This study suggests that feed localization can reduce nutrient surpluses at the district level.It is necessary to improve manure management and increase the degree of integrated crop-livestock in smallholdings.In industrial farms,it is desirable to increase the liquid manure recycling ratio through cooperating livestock and crop production at the district level.