Abstract
We investigated the effects of anaerobic decomposition of organic matter on the amorphous Fe content and P transformations in four soils used for a flooded riceupland crop rotation. The soils were amended with 0, 0.5, and 1.0% organic matter as cellulose and kept flooded for 85 d. The anaerobic decomposition of organic matter significantly increased the amorphous Fe content and produced significant transformations in inorganic P fractions. The Al-P decreased and Fe-P and RS-P fractions increased, due to the anaerobic decomposition of organic matter. We concluded that the anaerobic decomposition of organic matter increased the transformation of crystalline iron into amorphous iron. This led to an increase in Fe-P and severe occlusion of P, resulting in the increase in RS-P fraction upon soil drainage.