Effect of Application of Organo-Mineral Fertilizers on Humic Acid Characteristics in Alluvial Soil

Humic acids were extracted from seven soil samples collected from an alluvial tract which had been fertilized for three years with fertilizers, manures and organo-mineral mixtures. The highest content of carbon, nitrogen, total functional groups, phenolic hydroxyl groups, E₄/E₆ quotient and 6N HCl hydrolyzable N were found in the humic acid extracted from the soil treated with enriched leaves. The results indicate that the formation of soil humic acids is affected by the type of fertilizer treatment to some extent and the differences occur mainly in the functional group content. Not much variations were observed in the absorption characteristics in the visible and infrared spectra of the humic acids by any of these treatments.