Abstract
<List> <ListItem><ItemContent> • Degree of integration of crop and livestock was insufficient on mixed smallholdings. </ItemContent></ListItem> <ListItem><ItemContent> • Liquid manure discharges on industrial farms hamper the closing of nutrient loops. </ItemContent></ListItem> <ListItem><ItemContent> • Coupling with local crop farms is encouraged to achieve integration of crop-livestock systems. </ItemContent></ListItem></List> <fig><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2095-7505-8-1-58/fase-20371-myf-tu1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2095-7505-8-1-58/FASE-20371-MYF-tu1.tif"/></fig> 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.
Highlights
The nitrogen (N) and phosphorus (P) losses from Chinese livestock systems in 2010 were 23 Tg and 4.6 Tg[1]
The main feed source (dry matter (DM) basis) of industrial pig farms was outside the province (70%), followed by within the province (20%) and the local district (10%)
8.9% of feed N and 13% of feed P were sourced from household cropland products, and 8.7% of excreted N and 14% of excreted P were returned to household cropland, 370 kg$ha–1$yr–1 N and 71 kg$ha–1$yr–1 P were applied to household farmland in manures
Summary
The nitrogen (N) and phosphorus (P) losses from Chinese livestock systems in 2010 were 23 Tg and 4.6 Tg[1]. Pork and dairy milk production systems accounted for 23% and 8% of N losses and 18% and 7% of P losses[2,3]. Pig and dairy cattle production systems produce both liquid and solid manures. Livestock farms lack sufficient arable land area and suitable machinery to apply manures, especially liquid manures, it is usually directly discharge[4]. Direct discharges (manure to water bodies or landfill) of manure N and P in 2010 were 5.4 Tg and 1.9 Tg, direct discharges have become a major source of water pollution in China[1]. There is an urgent need to evaluate the N and P balances of pig and dairy farms
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