Effects of drainage on the chemistry of acid sulfate soils

Acid sulfate soils develop in coastal areas of the world, usually in the tropics. Due to their coastal proximity and their nearly level slope, these soils often appear to be ideally suited for agricultural usage following draining. The first stage of acid sulfate soil formation involves the production of pyrite, which occurs in clayey intertidal environments such as mangrove swamps, where tidal flushing is strong. The necessary prerequisites for pyrite formation are: sulfate, sulfate reducing bacteria, organic matter, iron, and alternate periods of anaerobic and aerobic conditions. The second major step in the formation of acid sulfate soils involves aeration of the pyritic sediments, which leads to pyrite oxidation and subsequent acid formation. Water management is a major management tool for acid sulfate soils. Oxidation and acidification can be stopped or prevented by maintaining a high water table. Waterlogging and soil reduction helps to remove acidity.