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

<p>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 CH<sub>4</sub> 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 CH<sub>4</sub> emissions by about 66% without impacting yield. In any strategy, CO<sub>2</sub> and N<sub>2</sub>O emissions should also be monitored to take advantage of the high carbon sequestration potential of rice and low potential N<sub>2</sub>O emissions. Careful water and fertilizer management can theoretically keep N<sub>2</sub>O emissions low. All three gases should be managed together, while sustaining or improving harvest yield, to create a sustainable rice production system.</p><p> </p><p>We now present 5 years of closed chamber measurements of N<sub>2</sub>O and CH<sub>4</sub> and compare them to the eddy covariance measurements of CH<sub>4</sub> and CO<sub>2</sub> 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 CH<sub>4</sub> emissions (74 to 100%), hence mitigating efforts need to focus on CH<sub>4</sub> emissions. Greater reduction of CH<sub>4</sub> 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 CO<sub>2</sub> uptake as soil organic matter via litter incorporation without increasing CH<sub>4</sub> emissions. </p>