Humic substances and functional groups of soil humus reserve developed under varied Agroecological units of South-central part of Maharashtra

A study was conducted on soils developed under varied agroecological units of Marathwada region at different altitudes. The physico-chemical properties of these soils were determined and humus fractionation was carried out according to the standard methods. These fractions were further analyzed for their functional groups. The results revealed that there was a distinct effect of the major environmental factors namely rainfall and altitude, on the distribution of soil humus into humin, humic acid and fulvic acid fractions as well as the HA: FA ratio. Soil humus fractions decreased with increasing depth of soil irrespective of the agroclimatic zone studied. Humic substances had relatively high concentration of oxygen containing functional groups per unit weight. The total acidity, carboxylic and phenolic hydroxyl groups of humic and fulvic acids showed more or less similar content in the soils of different agroclimatic situations.