Impact of 38-year integrated nutrient management on soil carbon sequestration and greenhouse gas emissions of a rice-wheat cropping system

Abstract

Integrating chemical fertilizers and organic manures is critical for improving soil health, increasing crop production, and mitigating the adverse environmental effects of the rice-wheat cropping system (RWCS). Numerous attempts have been made to evaluate the influence of integrated nutrient management (INM) on both crop yields and greenhouse gas (GHG) emissions during a single crop growing season. However, few studies have quantified the impact across an entire rotation cycle in this cropping system, considering the CO₂ uptake due to soil carbon (C) sequestration and saving of chemical fertilizer in INM practices. Therefore, the study was conducted to quantify the effects of 38 years of INM in rice-wheat cropping system on C sequestration and GHG emissions. Five treatment combinations of fertilizer nutrients (NPK) alone and their partial substitution (25 % N) with organic sources either through farmyard manure (FYM) or wheat cut straw (WCS) or green manuring (GM) in rice, and only chemical fertilizers at different levels in succeeding wheat crop were studied for two years (2019–20 and 2020–21). The results showed that substituting 25 % fertilizer N with organic materials (FYM/WCS/GM) in rice and using 25 % less NPK in wheat for 38 years significantly improved soil properties, including SOC sequestration, and increased crop yield (except WCS). INM increased the GHG emissions over chemical fertilization (100 % NPK), but the GHGI (greenhouse gas intensity) was equivalent, except for the usage of WCS in RWCS. Overall, in RWCS, INM via substituting 25 % fertilizer N with FYM/GM in rice and applying 75 % NPK in wheat had lower GHGI than only chemical fertilizer application, indicating the advantages of these amendments for increasing soil health, crop production, and climate change mitigation. Further research is required to determine the correlation between the mineralization patterns of added organic amendments, soil C fractions during critical crop growth stages, and GHG emissions.