CHEMICAL-VARIABLES AFFECTING THE LIME REQUIREMENT DETERMINATION OF TROPICAL PEAT SOILS

The carboxyl group in humic acid (HA) is the major functional group in fluencing the soil acidity. The soil pH(H2O), %HA, buffer capacity, mi lliequivalent (meg) COOH, meg phenolic OH, and meg total acidity/100 g peat are significantly correlated with lime requirement (LR). The LR of peat soils with high soil pH is low regardless of the effect of oth er variables (%HA, meg COOH, meg phenolic OH, meg total acidity/100 g peat, and buffer capacity). This indicates that the soil pH(H2O) is an important factor influencing the LR of tropical peat soils. Milliequi valent COOH/g HA is inadequate criteria for determining peat soil acid ity component as it changes with humification. However, meg COOH/100 g peat (meg COOH/g HA x %HA) is significantly correlated with LR and th is implies the importance of %HA as soil acidity component in tropical peat soils. Buffer capacity is significantly correlated with %HA, meg COOH, meg phenolic OH, and meg total acidity/100 g peat. Stepwise mul tiple regression analysis indicates that pH(H2O), %HA, and buffer capa city are factors influencing the LR of tropical peat soils.