Effect of Organic Matter and Soil Water Content on the Transformation of Native Soil Zinc

A laboratory incubation experiment was conducted to study the effect of soil water (continuous submergence and alternate submergence and saturation) and organic matter on the distribution of native soil Zn in different fractions in lowland rice growing soils. With time of incubation, the recovery of Zn in water soluble plus exchangeable (WE), organically complexed (OM) and crystalline FeO-bound fractions (CFeoX) decreased with a concomitant increase in MnO-bound-(MnOX) and amorphous FeO bound-(AFeOX) fractions under all the treatments. Generally, the magnitude of decrease/increase in these fractions may be attributed to higher CEC, organic carbon, free Fe and Mn contents of the soil. The magnitude of decrease/increase in different zinc fractions is more prominent under continuous submergence than under alteniate submergence and saturation condition. Organic matter increased the Zn transformation into MnOX-Zn, OM-Zn and AFeOX-Zn fractions but decreased the transformation of zn into WE-Znand CFeOX-Zn fractions. Application of organic matter under continuous submergence exerted a significant effect on all Zn fractions except the OM-Zn fraction.