Molecular Weight Distribution in Some Soil Humic Acids

The study pertains to molecular weight distribution of humic acids in soils occurring at varying altitudes under different climatic conditions and forest vegetations in some parts of the eastern Himalayas. For comparison, three other soils under different agroclimatic situations have also been studied. The results show that in both coniferous and deciduous forest soils fulvlc acids predominate over humic acids and the humus under coniferous cover contains more than 65% fulvic acids. The values in case of deciduous vegetation are much lower. The soil humic acids under conifers contain a larger proportion of high molecular weight fractions and reverse is the case with deciduous forests. The total acidity of humic acids having higher proportion of low molecular weight fractions is more than those containing larger proportion of high molecular weight fractions.