Role of Low-Molecule-Weight Organic Acids and Their Salts in Regulating Soil pH

The process of organic materials increasing soil pH has not yet been fully understood. This study examined the role of cations and organic anions in regulating soil pH using organic compounds. Calcareous soil, acid soil, and paddy soil were incubated with different simple organic compounds, pH was determined periodically and CO2 emission was also measured. Mixing organic acids with the soil caused an instant decrease of soil pH. The magnitude of pH decrease depended on the initial soil acidity and dissociation degree of the acids. Decomposition of organic acids could only recover the soil pH to about its original level. Mixing organic salts with soil caused an instant increase of soil pH. Decomposition of organic salts of sodium resulted in a steady increase of soil pH, with final soil pH being about 2.7-3.2 pH units over the control. Organic salts with the same anions （citrate） but different cations led to different magnitudes of pH increase, while those having the same cations but different anions led to very similar pH increases. Organic salts of sodium and sodium carbonate caused very similar pH increases of soil when they were added to the acid soil at equimolar concentrations of Na^＋. The results suggested that cations played a central role in regulating soil pH. Decarboxylation might only consume a limited number of protons. Conversion of organic salts into inorganic salts （carbonate） was possibly responsible for pH increase during their decomposition, suggesting that only those plant residues containing high excess base cations could actually increase soil pH.

增加土壤 pH 的器官的材料的过程还没是充分理解。这研究在用有机化合物调整土壤 pH 检验了阳离子和器官的阴离子的角色。石灰性土壤，酸性土，和水稻土与不同简单有机化合物被孵化。pH 周期性地被决定， CO2 排放也被测量。与土壤混合有机酸引起了土壤 pH 的立刻的减少。pH 减少的大小取决于起始的土壤酸度和酸的分离度。有机酸的分解能仅仅恢复土壤 pH 到关于它的原来的水平。与土壤混合器官的盐引起了土壤 pH 的立刻的增加。钠的器官的盐的分解导致了土壤 pH 的稳定的增加，与在附近是的最后的土壤 pH 在控制上的 2.7 3.2 个 pH 单位。有一样的阴离子(柠檬酸盐) 的器官的盐但是不同阳离子导致了 pH 增加的不同大小，当那些有时一样的阳离子但是不同阴离子导致了很类似的 pH 增加。当他们在 Na+ 的 equimolar 集中被加到酸性土时，钠和钠碳酸盐的器官的盐引起了土壤的很类似的 pH 增加。结果建议阳离子在调整土壤 pH 起了一个中央作用。去碳酸基可能仅仅消费一小部分质子。进无机的盐(碳酸盐) 的器官的盐的变换在他们的分解期间为 pH 增加可能负责，建议仅仅包含高过量底阳离子的那些植物残余能实际上增加土壤 pH。