Organic amendments influence soil quality and carbon sequestration in the Indo-Gangetic plains of India

Soil organic carbon is considered to be of central importance in maintaining soil quality. We assessed the effects of a range of commonly applied organic and inorganic amendments on soil quality in a rice-wheat cropping system in the Indo-Gangetic plains of eastern India and evaluated the carbon sequestration potential of such management approaches using a 25 year old long-term fertility experiment. Results showed that there were significant increases in soil nutrient availability with the application of farm yard manure (FYM @ 7.5 t ha⁻¹), paddy straw (PS @ 10 t ha⁻¹) and green manure (GM @ 8 t ha⁻¹) along with inorganic fertilizer. Both microbial biomass C and mineralizable C increased following the addition of the organic inputs. Continuous cultivation, without application of organic inputs, significantly depleted total C content (by 39-43%) compared with treatments involving the addition of organic amendments. A significant increase in the non-labile C fraction resulted from both organic and inorganic amendments, but only 26, 18 and 6% of the C applied through FYM, PS and GM, respectively was sequestered in soils. A significant increase in yield of kharif rice was observed as a result of the addition of these organic amendments.