Manure Nutrients of Pig Excreta Relative to the Capacity of Cropland to Assimilate Nutrients in China

Abstract Manure is the major pollution source of the pig-rearing industry and its application as a natural fertilizer is the main way to dispose it. As excess manure brings potential risks to surface and ground water, it is important to determine the capacity of croplands to assimilate manure nutrients. In this study, manure nutrients obtained from pig excretions from smallholder, specialized and concentrated livestock industries were estimated on a provincial level in China in 2002 and 2008. This was then correlated to the capacity of the cropland to assimilate the nutrients through the planting of 20 crops. The manure nitrogen (N) increased from 1.907 millions tonnes (Mt) in 2002 to 2.247 Mt in 2008, while the manure phosphorus (P) increased from 0.634 Mt in 2002 to 0.733 Mt in 2008. The specialized and concentrated pig industries were the major sources of manure nutrients. Moreover, manure nutrients generated from the Henan, Hunan, Hubei, Sichuan, Guangdong, Liaoning, Guangxi, Heilongjiang and Shandong provinces contributed to more than 60% of the total levels in China. The specialized pig industries in the northern and eastern provinces generated more manure N than the southwestern provinces and overall, this value grew in most provinces from 2002 to 2008. The total levels of manure production were higher in the eastern and southern than in western and northern. ‘Especially, the concentrated pig-rearing industries grew at a rapid pace and made an important contribution to excess manure nutrients. The correlation analysis of manure nutrients generated to cropland assimilation capacity showed that the capacity was adequate for the pig manure nutrients. This study demonstrates that Beijing, Tianjin Guangdong, Hunan and Sicuan should take measures to cut down the amount of manure nutrients, and determining the pig-rearing industrial scale according to the nutrient capacity of the available land is a must for avoiding the risk of excess manure nutrients.