Greenhouse gas emissions mitigation with alternate wetting and drying irrigation of rice agriculture

Rice production contributes roughly 11% of global CH4 anthropogenic emissions while producing food for over 3 billion people. The alternate wetting and drying (AWD) irrigation practice for rice has the potential to conserve water while reducing CH₄ emissions through the deliberate, periodic introduction of aerobic soil conditions. Our work in the US Mid-South rice production region has demonstrated, using the eddy covariance method on adjacent fields, that AWD can reduce field CH₄ emissions by about 66% without impacting yield. In any strategy, CO₂ and N₂O emissions should also be monitored to take advantage of the high carbon sequestration potential of rice and low potential N₂O emissions. Careful water and fertilizer management can theoretically keep N₂O emissions low. All three gases should be managed together, while sustaining or improving harvest yield, to create a sustainable rice production system.

 

We now present 5 years of closed chamber measurements of N₂O and CH₄ and compare them to the eddy covariance measurements of CH₄ and CO₂ to derive a more thorough perspective on the net greenhouse gas (GHG) emissions or global warming potential basis of rice production from the highly productive, mechanized, humid, US Mid-South. Global warming potential of GHG emissions from rice systems was dominated by CH₄ emissions (74 to 100%), hence mitigating efforts need to focus on CH₄ emissions. Greater reduction of CH₄ emissions can be achieved by proper AWD management practice combined with adequate N fertilization. We end with a comment on the upcoming challenge of how to sequester CO₂ uptake as soil organic matter via litter incorporation without increasing CH₄ emissions.