An Investigation of Changes in Fractional Size and Chemistry of Soil Organic Matter

Soil organic matter is an indicator of soil, agriculture and environmental quality, playing important roles in soil strength and sound environmental functions. Size and chemical fractionation of soil organic matter are long-standing approaches in clarifying their key role in soil processes. Twenty seven surface samples (0-20 cm) and 6 pedons from different landform units were sampled and described according to USDA, 2002 and by means of illustrating the surface as well as vertical distribution of different size and varied chemical fractions of organic carbon. Physico-chemical, mineralogical, physical and chemical fractionations were carried out following standard methods. The results revealed that organic carbon content increases by decrease in the fraction size, reaching its maximum at <250 μ. Also it was observed that 2:1 expandable clays show relatively higher capability in organic carbon complication in comparison with the other mineralogical suits. The results for chemical fractionation demonstrated that humic to fulvic acid ratio increases by increase in organic matter input, itself being followed by increase in soil biological activity.