Tillage effects on energy use and greenhouse gas emission in wheat-cotton rotation

Crop production process utilizes input energy and produces some biomass energy as output.  During this process, greenhouse gases (GHGs) are also emitted which can make environmental risks. In this study, input and output energies, energy indices, and GHG emissions arising from inputs were estimated for wheat-cotton rotation under different tillage practices in Fars province. The study was conducted as a randomized complete plot experimental design with three tillage treatments and four replicates. Tillage methods included conventional tillage (CT), reduced tillage (RT), and no tillage (NT). Results showed that NT and RT decreased energy consumption in wheat and cotton production by 1.53 and 1.19%, respectively as compared to the CT due to less fuel and machinery utilization. More than 72% of energy requirement for wheat and cotton production was consumed by irrigation water and electricity for pumping irrigation water in all tillage methods. Conventional tillage resulted in the highest output energy, energy ratio, and energy productivity in wheat-cotton rotation compared to RT and NT. Total GHG emissions for wheat and cotton production were estimated to be 51829, 51608, and 51529 kg CO2e ha-1 in CT, RT, and NT, respectively indicating that NT and RT slightly reduced GHG emission compared to CT (0.6 and 0.4%, respectively). Results of this study indicated that irrigation showed the highest share in total energy requirement and GHG emission of wheat and cotton production in semi-arid climate condition of Fars province; therefore, total input energy and GHG emissions could be markedly reduced by using more efficient irrigation systems.