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