Global warming potential and greenhouse gas emission under different soil nutrient management practices in soybean–wheat system of central India

Soil nutrient management is a key component contributing to the greenhouse gas (GHG) flux and mitigation potential of agricultural production systems. However, the effect of soil nutrient management practices on GHG flux and global warming potential (GWP) is less understood in agricultural soils of India. The present study was conducted to compare three nutrient management systems practiced for nine consecutive years in a soybean–wheat cropping system in the Vertisols of India, in terms of GHG flux and GWP. The treatments were composed of 100% organic (ONM), 100% inorganic (NPK), and integrated nutrient management (INM) with 50% organic + 50% inorganic inputs. The gas samples for GHGs (CO₂, CH₄, and N₂O) were collected by static chamber method at about 15-day interval during 2012–13 growing season. The change in soil organic carbon (SOC) content was estimated in terms of the changes in SOC stock in the 0–15 cm soil over the 9-year period covering 2004 to 2013. There was a net uptake of CH₄ in all the treatments in both soybean and wheat crop seasons. The cumulative N₂O and CO₂ emissions were in the order of INM > ONM > NPK with significant difference between treatments (p < 0.05) in both the crop seasons. The annual GWP, expressed in terms of CH₄ and N₂O emission, also followed the same trend and was estimated to be 1126, 1002, and 896 kg CO₂ eq ha⁻¹ year⁻¹ under INM, ONM, and NPK treatments, respectively. However, the change in SOC stock was significantly higher under ONM (1250 kg ha⁻¹ year⁻¹) followed by INM (417 kg ha⁻¹ year⁻¹) and least under NPK (198 kg ha⁻¹ year⁻¹) treatment. The wheat equivalent yield was similar under ONM and INM treatments and was significantly lower under NPK treatment. Thus, the GWP per unit grain yield was lower under ONM followed by NPK and INM treatments and varied from 250, 261, and 307 kg CO₂ eq Mg⁻¹ grain yield under ONM, NPK, and INM treatments, respectively.