Farming tactics to reduce the carbon footprint of crop cultivation in semiarid areas. A review

The human population on the planet is estimated to reach 9 billion by 2050; this requires significant increase of food production to meet the demands. Intensified farming systems have been identified as a viable means to increase grain production. However, farming intensification requires more inputs such as fertilizers, pesticides, and fuels; all these emit greenhouse gases and have environmental consequences. An overwhelming question is: can farming practices be improved which enables yield increase with no cost to the environment? Here, we present seven key farming tactics that are proven to be effective in increasing grain production while lowering carbon footprint: (1) using diversified cropping systems can reduce the system's carbon footprint by 32 to 315 % compared with conventional monoculture systems; (2) improving N fertilizer use efficiency can lower the carbon footprints of field crops as N fertilizer applied to these crops contributed 36 to 52 % of the total emissions; (3) adopting intensified rotation with reduced summerfallow can lower the carbon footprint by as much as 150 %, compared with a system that has high frequency of summerfallow; (4) enhancing soil carbon sequestration can reduce carbon footprint, as the emissions from crop inputs can be partly offset by carbon conversion from atmospheric CO2 into plant biomass and ultimately sequestered into the soil; (5) using reduced tillage in combination with crop residue retention can increase soil organic carbon and reduce carbon footprints; (6) integrating key cropping practices can increase crop yield by 15 to 59 %, reduce emissions by 25 to 50 %, and lower the carbon footprint of cereal crops by 25 to 34 %; and (7) including N-2-fixing pulses in rotations can reduce the use of inorganic fertilizer, and lower carbon footprints. With the adoption of these improved farming tactics, one can optimize the system performance while reducing the carbon footprint of crop cultivation.