Fractionation of soil organic matter in laterite soils of Kerala

Abstract

Soil samples collected from faten'te zones of Kerala were examined for fractions and elemental components of organic matter. The humic acid accounted for 28.28 percent of organic matter. Humic acid was found to be significantly and positively correlated with organic C (r=0.8520**), total nitrogen (r = 0.7397**), clay (r= 0.7799**) and fulvic acid (r = 0-90S2**). Humic acid and fuivic acid maintained a constant proportion irrespective of the variation in content of organic matter. Fulvic acid accounted for 36.51 per cent of total organic matter. Significant and positive correlations were observed for fulvic acid with organic carbon (r=0.9618**), total N ;r = 0.891 3**) and humic acid (r= 0.8552**), The HA/FA ratio of soil organic matter ranged from 0.23 to 1.06 with a mean value of 0.78. Humin fraction accounted for 35.21 per cent of soil organic matter. Hunnin content was found to be positively and significantly correlated with total nitrogen (r —0.7374**) and organic carbon (r —0.6455**}. The mean contents of nitrogen, phosphorus, sulphur and potassium in soil organic matter were 7.34, 0.051, 6.96 and 0.32 per cent respectively.