Soil acidity components of tropical acid soils: Their roles in determining lime requirement values and the effect of lime upon them

Clay content, pH, organic matter content (%C), cation exchange capacity (CEC), exchangeable (exch.) Al, exch. Mn, exch. acidity (ACe), residual acidity (ACr), and total acidity (ACt) of 26 agricultural soils were determined. These were correlated with each other and also with lime requirement (LR) values to three pH targets, measured by various methods. The effect of lime on ACe, ACr, exch. Al, exch. Mg and soil pH was studied by moist CaCO3‐incubation. Organic matter content was the most influential factor in the buffering capacities of these soils against changes in pH. Although ACr dominated the soil acidity components, ACe was the best index of LR of these soils and was well correlated with all LR values measured by the different methods. Exchangeable Al and Mn were virtually eliminated in all soils at a soil pH of about 5.5.