Fe(III) Reduction Potential in Rice Soil as Influenced by Microbial Communities Under Flooded Condition

Abstract

In the present investigation, soil samples collected from different rice growing tracts were assessed for temporal changes in iron reduction and fractions of different iron pools under submergence condition. Results suggest that potential for Fe(III) reduction is largely due to biological means as the amounts of reduced or dissolved Fe(II) in the antibiotics-treated or steam sterilized soil samples were negligible compared to control. As the concentration of iron in a soil depends initially on the nature of its parent material, the crystalline forms of iron constituted about 67 to 89 %; non-crystalline forms of iron ranged from 11 to 33 % and microbially reducible iron ranged from 6-18 % of total chemically extractable iron. XRD analysis attributed the presence of quartz, muscovite, biotite, carbonates and fluorapatite in the analyzed samples. The population densities of iron reducing microorganisms were about 105 to 106 g-1 soil, as enumerated by the MPN, suggesting the addition of glucose and acetate extensively support iron reducers in soils under flooded condition.