Effect of organic manures and humic acids on changes in hydro-lysable organic fractions of nitrogen in a Typic Haploumbrepts soil

摘要

A pot experiment was conducted to study the changes in hydrolysable organic nitrogen fractions in a Typic Haploumbrepts soil amended with N sources (urea, farm yard manure, compost, vermicompost, N-enriched compost and humic acids extracted from the corresponding manures) equivalent to 20 kg N ha(-1). Results show that hydrolysable organic N forms were accumulated more in soil treated with N over the control. Among the different forms, hydrolysable NH4+ , hexosamine-N and amino acid-N were mineralized and contribute to available N. Comparatively higher amounts of hydrolysable NH4+, hexosamine-N, (serine + threonine)-N and amino acid-N were found in soil treated with humic acids over the corresponding organic manures. Contribution of hydrolysable forms of N to available N is a positive indication for substitution of chemical N by organic sources. Organic manures mineralized at a faster rate compared with the corresponding humic acids.