Estimation on farmland carrying capacity of animal manure in soil acidification prevention and control

<bold>Objective</bold> Southern China is located in the tropical and subtropical monsoon climate region，characterized by synchronized rainfall and heat with abundant precipitation，This climatic condition drives intense chemical decomposition of soil minerals and leaching of base cations.Soil acidification in southern China is increasingly exacerbated，emerging as the main obstacle to improving the quality of cultivated land.The study aims to solve the problem of soil acidification and scientific application of manure in southern China，to synergistically achieve regional integrated crop-livestock systems and soil acidification mitigation and control. <bold>Method</bold> The modeling of farmland carrying capacity of animal manure in soil acidification prevention was carried out in key acidification areas in southern China.According to the mechanism of farmland soil acidification，the net acid production of farmland soil system in Hunan and Jiangxi provinces was calculated using 723 long-term paddy rice positioning test observation data from Qiyang Station in Hunan Province，Taoyuan Station in Hunan Province and Yingtan Station in Jiangxi Province.Assuming that the alkalinity of animal manure was equal to the net acid production of farmland soil system，the required livestock manure amount per hectare for acidification prevention and control can be estimated by incorporating the manure's alkalinity value.Based on the parameters such as animal manure collection and treatment，the optimal animal breeding amount was dervied. <bold>Result</bold> The net acid production of farmland soil system in Hunan and Jiangxi provinces was 5.9-7.9 and 6.8-8.9 keq per hectare，respectively.Among them，the hydrogen ion production in the nitrogen cycle process in Hunan Province was 0.7 keq per hectare，the hydrogen ion production in the nitrogen cycle process in Jiangxi Province was 0.8-1.0 keq per hectare；while the hydrogen ion production in the base ion absorption process in the two provinces was 6.5-8.9 and 7.3-9.9 keq per hectare，respectively，and the hydrogen ion consumption in the anion absorption process were 1.3-1.8 and 1.5-2.1 keq per hectare，respectively.The hydrogen ion production in the base ion absorption process was the main part of the acid production in the farmland soil system.Based on the calculation model，the carrying capacity of animal manure of swine，dairy cattle，beef cattle，broiler and layer in Hunan Province was 152.8-202.7 heads per hectare，2.4-3.2 heads per hectare，5.6-7.5 heads per hectare，701.6-931.0 feathers per hectare and 141.4-187.7 feathers per hectare，respectively；In Jiangxi Province，it was 146.9-192.7 heads per hectare，3.4-4.5 heads per hectare，5.5-7.2 heads per hectare，798.9-1 047.8 feathers per hectare and 115.5-151.5 feathers per hectare，respectively. <bold>Conclusion</bold> Considering the need to prevent soil acidification，the animal breeding industry in Hunan and Jiangxi provinces had great potential for future development.It was recommended to increase the application of manure moderately to synergistically achieve soil acidification prevention and integration of planting and breeding，while the risk of agricultural non-point source pollution caused by surplus nutrients in farmland needed to be prevented and controlled.