See more from this Session: Symposium--Global Importance and Progress of Reducing Anthropogenic Emissions of Nitrous Oxide From Cropping Systems: I
Tuesday, October 18, 2011: 11:45 AM
Henry Gonzalez Convention Center, Room 211, Concourse Level
Agricultural greenhouse gas (GHG) emissions contribute approximately 12% to total global anthropogenic GHG emissions. Cereals (rice, wheat and maize) are the largest source of human calories, and it is estimated that world cereal production must increase 1.3% annually to 2025 in order to meet growing demand. Sustainable intensification of cereal production systems requires maintaining high yields while reducing environmental costs. We conducted a meta-analysis (62 study sites and 328 observations) to test the hypothesis that the Global Warming Potential (GWP = CH4+N2O) of rice, wheat, and maize, when expressed per ton of grain (yield-scaled GWP), is similar, and that lowest values for each cereal is achieved at near optimal yields. Results show that the GWP of rice (3757 kg CO2 eq ha-1 season-1) was higher than wheat (662 kg CO2 eq ha-1 season-1) and maize (1399 kg CO2 eq ha-1 season-1). The yield-scaled GWP of rice was about four times higher (657 kg CO2 eq Mg-1) than wheat (166 kg CO2 eq Mg-1) and maize (185 kg CO2 eq Mg-1). Across cereals, the lowest yield-scaled GWP values were achieved at 92% of maximal yield and was about twice as high for rice (279 kg CO2 eq Mg-1) than wheat (102 kg CO2 eq Mg-1) or maize (140 kg CO2 eq Mg-1), suggesting greater mitigation opportunities for rice systems. In rice, wheat and maize, 0.68%, 1.21% and 1.06% of N applied was emitted as N2O, respectively. In rice systems, there was no correlation between CH4 emissions and N rate. Finally, when evaluating issues related to food security and environmental sustainability other factors including cultural significance, the provisioning of ecosystem services, food security, and human health and well-being must also be considered.