Soil organic carbon stocks and carbon dynamics under organic and conventional farming systems in Indo-Gangetic Plains

The long-term effect of organic farming practices were evaluated on soil organic carbon stocks (SCS) and its fractions in texturally divergent soils of Haryana. Surface (0-15 cm) soil samples were collected from 25 organic farms and adjoining conventional farms from 11 districts of Haryana. Soil samples were analyzed for pH, EC, calcium carbonate (CaCO3), soil organic carbon (SOC) and its fractions, viz. light fraction C (LOC), particulate organic C (POC) and mineral associated C (MOC). Results revealed that shifting from conventional to organic farming had no effect on soil pH and EC but reduced the CaCO3 significantly (P<0.05). Soil under organic farming exhibited a significant increase in the SOC from 5.1 to 6.2 g/kg and SCS from 11.2 to 13.3 Mg/ha as compared to soils under conventional farming. The light fraction C was most sensitive to management practices, followed by POC and MOC fraction. The magnitude of increase in LOC, POC and MOC under organic soils was 48.9, 23.6 and 14.7%, respectively as compared to conventionally managed soils. Different organic carbon pools in various fractions followed the order MOC> POC> LOC. The study concluded that shift from conventional to organic farming could be adopted or promoted for sustainable management of soil organic C stocks.