Different fractions of iron in paddy growing soils in selected villages of Gangavati taluka in North Karnataka, India

Sixty surface (0-20 cm) soil samples each from the farmers paddy field collected from different villages of Gangavati taluka in North Karnataka in the year 2010-2011. The two years soil samples were pooled and handled for laboratory analysis. Fractionation of iron in soil samples carried out with standard procedure. Distributions of different forms of iron in twelve village paddy growing soils were studied. The results showed that more than 31.48% in Karatagi sample and 71.91% in Maralanahalli sample of total iron occurred as free and amorphous bound iron, where as water soluble iron occurred only in 0.03% in Karatagi sample and 1.17% in Rampura soil samples. Soil contained water soluble iron from 0.11 to 4.62 ppm, exchangeable iron from 0.22 to 3.93 ppm, amorphous iron oxide bound iron from 109.61 to 456.81 ppm, crystalline iron oxide bound iron from 21.48 to 332.41 ppm and residual iron 37.27 to 216.45 ppm. In this fractions water soluble and exchangeable iron was low in all the soils when compared to other fractions, still it is very important from the plant availability point of view. Amorphous iron oxide bound form of iron dominated when compared to water soluble iron, exchangeable iron, crystalline iron oxide bound iron and residual iron fractions.