Iron toxicity is a widespread nutrient disorder that affects rice growing in inland swamps and on irrigated lowland soils throughout the humid forest and savanna zones of West Africa. It has been reported to reduce lowland rice yields in West Africa by 12-100%, depending on the intensity of the toxicity and the tolerance of the rice cultivar (Sahrawat et al 1996). The disorder occurs when large amounts of iron are mobilized in situ or when an inflow of iron occurs from adjacent upper slopes, especially in the inland valley systems of West and Central Africa. In mineral soils, the occurrence of iron toxicity is associated with a range of concentration of ferrous ions in the soil solution. Light-textured soils high in extractable acidity are especially prone to iron toxicity (Moormann and van Breemen 1978). It is also known that a high concentration of iron in solution decreases the absorption of other nutrients, especially phosphorus (P), potassium (K), and zinc (Zn) (Yoshida 1981).