In acid sulfate soils (ASS), it is well established that sulfuric soil acidity is managed by application of a neutralising agent and sulfidic soil oxidation is prevented by water table management. This review summarizes recent studies using organic matter in amelioration of sulfuric soil acidity and curtailing of sulfidic soil oxidation by discussing the changes induced on soil pH, Eh and sulfate contents under varying soil moisture regimes. Increase in low pH, low Eh values and reduction in sulfate content have been observed in sulfuric and sulfidic soil following organic matter amendment under aerobic and anaerobic soil conditions. When organic matter co-existed with live plants, pH decreased with correspondingly high Eh values and high sulfate contents in almost all cases, even under anaerobic soil conditions. Practical consideration shows that application of organic matter by incorporation and spot application as surface mulch followed by establishment of plants under general soil use and management conditions create microniches conducive for root growth and negate the mechanisms that lead to severe acidification associated with live plants.
Keywords: Acid sulfate soils, organic matter, live plants, pH, redox potential, sulfate content