Fe-P pools as phosphorus source for rice in acid sulfate soils

Acid sulfate soils (ASS) are rich in Fe, low in available P, and low in soil pH. In acid soils, low P availability is associated with high Fe concentration, which has a high capability in P retention. The reactivity of Fe oxyhydroxides turns large proportions of soil P into insoluble or unavailable form. This review paper is addressed to provide new insights into the Fe and P relationship as the P source for rice (Oryza sativa L.) in ASS. Fertilizer application did not significantly alter P solubility in soil solution due to high reactivity and retention power of Fe mineral in ASS, but rice cultivation practice such as water management and soil amelioration has influenced formation, crystallization and character of Fe mineral. Subsequently determining adsorption and desorption of P. Soil waterlogging and drying alternately during rice cultivation have change soil pH and redox potential (Eh), causing dissolution of P from vivianite and reduction of Fe(III)-P to Fe(II)-P. We summarize that Fe-P pools (amorphous-Fe-P) in the rice fields in ASS are categorized as readily available or labile P fraction.