Acidity reduction receiving long-term pig manure application in red soil

Abstract While the application of manure to improve soil quality has attracted attention, the effect of pig manure application rates on soil fertility and acidity remains poorly understood. This study analyzed the changes in and correlations between soil acidity, pH buffer capacity (pHBC), soil chemical properties and crop yields after 8 years of pig manure application at different rates (i.e., 0, 7.5, 15, 30, and 45 t·ha-1) in red soil. Crop yield, soil nutrients, pH, pHBC, iron activation, and exchangeable base cations increased with increased pig manure application rates. Soil fertility and pHBC were significantly enhanced when the application rate was larger than 15 t·ha-1. At 30 and 45 t·ha-1, pH values increased significantly while exchangeable acid decreased (41.3% and 52.8%) compared to no pig manure input. Crop yields were positively related to soil pH, but negatively correlated with soil exchangeable hydrogen and exchangeable aluminum. Redundancy analysis revealed pH and pHBC to be positively correlated with exchangeable base cations, total phosphorus, total nitrogen, soil organic carbon, and amorphous iron oxide. In conclusion, crop yield could be improved by adjusting soil acidity characteristics, and the application of pig manure reduced soil acidity, with an optimal application rate of 15–30 t·ha-[1]. [1]Hunan Soil and Fertilizer Institute, Changsha, 410125, China. 2Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences/ Key Laboratory of Agricultural Environment, Ministry of Agriculture and Rural Affairs of P.R.China, 100081, Beijing, China. 3Hunan Agricultural University, Changsha, 410128, China. *email: longzd313@hunaas.cn; sungeng@hunaas.cn.