Estimating Spatial Differences in Methane Emissions to Identify Sustainable Rice Sources

Commercial rice (Oryza sativa L.) buyers and a growing consumer market for sustainable agricultural products are driving agriculture to be more conscious about production practices and associated environmental effects, such as greenhouse gas emissions. Globally rice production has been identified as a significant source of atmospheric methane (CH4) emissions. This study extends current knowledge by using a procedure to quantify spatial differences in CH4 emissions as well as CH4 efficiency levels (kg rice [kg CH4-C](-1)) across the mid-southern United States, where over 75% of all US rice is produced. This study focuses on existing rice production practices that are known to directly affect CH4 emissions: variety selection, crop rotation, and soil texture. Historical data on varietal selection, crop rotations, and soil texture were used to estimate CH4 emissions from 2005 through 2014. Results showed that rice produced on clay-textured soils with a rice-soybean rotation sown with a hybrid variety has the largest CH4 emissions efficiency among the management practice combinations evaluated. Results also demonstrated that any deviation from this optimal combination cannot be mitigated through realistic increases in yields, as it would take a 177% increase in yield for the hybridclay-rice to achieve the same efficiency as the hybrid-clay-soybean [Glycine max (L.) Merr.] combination. Results of this study provide commercial rice buyers, producers, and consumers with critical information regarding the drivers of spatial variations in sustainable rice production. Furthermore, these results give insights to producers and policymakers regarding which production practices and locations could benefit from increased demand for sustainable products and more restrictive environmental policies.