Long-term effect of different integrated nutrient management on soil organic carbon and its fractions and sustainability of rice–wheat system in Indo Gangetic Plains of India

Declines in soil organic carbon (SOC) are well-documented in India after the intensification of agricultural practices. SOC contributes to several characteristics of soil that are important for cultivation, including soil aeration, storage of nutrients, fertility, resistance to compaction, and water-holding capacity. The objective of this study was to determine the effect of nutrient management method on SOC and its derivatives as well as the overall sustainability, estimated by the sustainable yield index, of a rice-wheat system under these different methods. A total of 4.7 million hectares in the Trans Gangetic Plains, Upper Gangetic Plains, Middle Gangetic Plains, and Lower Gangetic Plains were studied under different combinations of inorganic and organic (farm yard manure, green manure) nutrient application beginning in 1983-1986 and ending in 2009. The authors found that substituting inorganic fertilizer with organic resulted in higher SOC, particulate organic carbon (POC), microbial biomass carbon (MBC) concentration, and rates of carbon sequestration. Sequestration rates were also higher in humid (Lower and Middle Gangetic Plains) versus semiarid climates (Trans and Upper Gangetic Plains). The authors call for further long-term studies of the Indo Gangetic Plains, particularly in quantifying the relationship between carbon sequestration and soil GHG emissions, in order to continue to develop recommendations and best practices suitable for local agricultural enterprises.