Characterization of Humic and Fulvic Acids Extracted from Two Major Soil Groups of Assam

Humic andfulvic acids extracted from some soils belonging to Inceptisols and Alfisols of Assam were characterised by elemental analysis, functional groups determination, gel permeation chromatography, E₄:E₆ ratio, UV and IR spectroscopy. Fulvic acid fraction predominated over humic acid fraction in almost all soils. Humic acid contained more C, H and N than fulvic acids. The contents of function algroups of humic and fulvic acids extracted from Alfisol were higher than those from Inceptisol. Gel permeation chromatography on a Sephadex G-50 column showed the presence of three fractions in humic acids and two fractions in fulvic acids from most of the soils indicating heterogenesis of humic substances. UV-spectra of humic acids showed higher absorption than fulvic acids. The IR-spectra of humic acids differ from fulvic acids mainly in respect of a medium absorption band at 1725 cm⁻¹ and absence of 1540 cm⁻¹ band and band near 1025 cm⁻¹.