Carbon footprint and greenhouse gas emissions from rice based agricultural systems calculated with a co-designed carbon footprint calculation tool

Abstract. There are many cropping systems followed in Floodplain soils for enhancing cropping intensity for increasing crop production, but greenhouse gas (GHG) emissions balances of agricultural systems are rarely reported. To estimate the carbon (C) footprints of agricultural products a co-designed C footprint calculation tool with a life cycle assessment approach was used in major cropping systems in Bangladesh: rice-rice-rice (R-R-R/boro-aus-aman), rice-fallow-rice (R-F-R/boro-fallow-aman), maize-fallow-rice (M-F-R), wheat-mungbean-rice (W-M-R), and potato-rice-fallow (P-R-F). GHG emissions were estimated using the tool along with the field measurements. It was found that rice-based cropping pattern with dryland crops had higher nitrous oxide (N₂O) emissions (3.98 in maize, 3.89 in potato and 0.72 kg N₂O-N ha⁻¹ in mungbean) than sole rice-based (0.73 in boro, 0.57 in aus and 1.94 kg N₂O-N ha⁻¹ in aman) cropping systems but methane (CH₄) emissions were higher in sole rice-based patterns than dryland crops. Methane contributed to about 50–80 % of total GHG emissions from rice cultivation due to waterlogging conditions throughout the season. In R-R-R and R-F-R cropping patterns, the only ones including boro rice, had the highest total C footprint with 26.3 and 19.5 Mg CO₂e ha⁻¹, respectively while the P-F-R and M-F-R had the lowest C footprint with 13 Mg CO₂e ha⁻¹. Changes in soil organic C generally had a minor influence on C footprints in the studied systems, and only boro and aus from R-F-R and R-R-R patterns were relatively more suitable for reducing C footprint as they sequestered C in soil. Measured CH₄ and N₂O emissions agreed well with IPCC tier 1 estimates, but they were only available for boro, maize and wheat so further study is required for validation and suggesting suitable GHG mitigation strategies from agricultural fields.