A Life Cycle Assessment of Rice-Rice and Rice-Cowpea Cropping Systems in the West Coast of India

Crop diversification is essential in lowland rice cropping systems to achieve sustainability, improve soil health, and as a climate-resilient practice to reduce greenhouse gas (GHG) emissions. A life cycle assessment (LCA) was conducted for the farms in the west-coast region of India to assess the environmental impact of the rice-rice and rice-cowpea cropping systems. The life cycle impact assessment (LCIA) was evaluated in a "cradle-to-gate" perspective. A higher energy consumption was found in the rice-rice system (32,673 vs. 18,197 MJ/ha), while the net energy output was higher in the rice-cowpea system (211,071 vs. 157,409 MJ/ha). Energy consumption was 44% lower in the rice-cowpea system, which was coupled with a higher energy efficiency (11.6 vs. 4.8), attributed to the lower energy consumption and the higher energy output. Further, the results indicated an energy saving potentialin the rice-cowpea system due to the higher use of renewable resources such as farmyard manure. Field emissions, fertilizer production, and fuel consumption were the major contributors to the greenhouse gas (GHG) emissions in both cropping systems. The total GHG emissions were 81% higher in the rice-rice system (13,894 +/- 1329 kg CO2 eq./ha) than in the rice-cowpea system (7679 +/- 719 kg CO2 eq./ha). The higher GHG emissions in the rice-rice system were largely due to the higher use of fertilizers, diesel fuel, and machinery. Hence, diversifying the winter rice with a cowpea crop and its large-scale adoption on the west coast of India would provide multiple benefits in decreasing the environmental impact and improving the energy efficiency to achieve sustainability and climate resilience in rice-based cropping systems.