Acidification and buffering mechanisms of tropical sandy soil in northeast Thailand

Tropical sandy soils are highly susceptible to acidification as a consequence of intensive farming. We analyzed the dominant processes of acidification and neutralization in a sandy soil of cropland system in northeast Thailand. Proton budgets in the soil (Typic Ustipsamments) were quantified for a sugarcane field and a mango plantation by measuring ion fluxes associated with solute leaching and plant uptake. Soil acidification in the sugarcane field was caused mainly by excessive uptake of cations over anions by sugarcane and following product removal. Despite the small stocks of organic matter in the sandy soil, the net mineralization of the native soil organic matter can neutralize most of the acidity associated with product removal (68%) in the sugarcane field. Proton budgets have demonstrated the sensitivity of tropical sandy soils to acidification and potential roles of organic matter on acid neutralization.