Characteristics of Fe-Toxic Soils in the Flooded Valleys of the High Rainfall Zone of Tamil Nadu

The toxicity of Fe occurs mainly in poorly drained inland valleys often with lateral seepage and or upwelling Fe containing water, coastal saline-acid soils, peat soils, acid sulphate soil and other hydromorphic soils and others. Surface soil samples(0 – 20 cm depth) were collected from rice fields in the areas of the soils prone to varying degree of Fe toxicity in the high rainfall zone of Tamil Nadu and analysed for their physico-chemical characteristics. The Aquic Hapludalf recorded 62.5 per cent of the samples with > 40 mg/kg of water soluble Fe followed by Udic Rhodudalf (52.6%). The upwelling ground water caused the accumulation of Fe and subsequent precipitation resulted in the presence of reduce brown scum of iron oxides and hydroxide on the surface of the soil particularly along the border of the field. Fe accumulation also induced deficiency of P,K, Zn and bases viz., Ca and Mg.