Humic Acid Elemental Composition and Ratios
Carbon content of humic acid was significantly higher underAzadirachta indica plantation. Increase in TOC leads to increase in humic acid and hence carbon content. Carbon content increased with increase in year of reclamation. Abakumov et al. also reported increase in carbon content of humic acid with increase in year of reclamation (Abakumov et al.,2012). This increase probably due to increasing in TOC content with an increase in year of reclamation. Moreover, the humic acid C was positively correlated with less labile carbon(Table-8). We can conclude, the less labile pool of carbon had a significant contribution to humic acid formation. Humic acid nitrogen content was highest in the case of Azadirachta indica followed byDalbergia sissoo and Gmelina arborea . This may be due to presence of nitrogen-containing functional group in humic acid. C/N ratio had increased with increase in year of reclamation. This increase was attributed due to increase in carbon content with increase in year of reclamation. Highest C/N ratio was observed in case of Gmelina arborea indicating a high proportion of carbon than nitrogen under