Greenhouse Gas Emissions

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Cynthia Kallenbach and Leslie Peacock monitoring greenhouse gases at Russell Ranch. (Photo by Dennis Bryant.)

Greenhouse gas emissions from the agricultural sector account for six percent of the total U.S. greenhouse emissions. However, agricultural activities account for 72% of the total U.S. nitrous oxide (N2O) emissions (EPA, 2006). Researchers at Russell Ranch are investigating the effect of different practices and crop systems on greenhouse gas emissions. One important finding is that reducing tillage substantially decreases greenhouse gas emissions through reduced fuel use. Research at Russell Ranch has shown that winter cover crops increase N2O emission under furrow irrigation (Fig. 14). Sub-surface drip eliminates the increase in N2O emission seen with cover crops using furrow irrigation. Research at LTRAS suggests that the conversion to sub-surface drip irrigation from furrow irrigation has the potential to reduce greenhouse gas emissions. This is significant because many studies suggest that planting cover crops can lead to an increase in both CO2 and N2O emissions but when managed with sub-surface drip irrigation this effect may be reduced (Kallenbach, 2008).

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Nitrous oxide emissions by growing season (May to Sept) and the rainy season (Oct to April). WLCC= winter legume cover crop (vetch and pea mix), NCC= no cover crop, FI= furrow irrigation, SDI= subsurface drip irrigation (Kallenbach, 2008).