Fertilizer and Tillage Management Impacts on Non-Carbon-Dioxide Greenhouse Gas Emissions

Recent efforts have attempted to establish emission estimates for greenhouse gas (GHGs) from agricultural soils in the United States. This research project was conducted to assess the influence of cropping system management on non-CO2 GHG emissions from an eastern Corn Belt Alfisol. Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] rotation plots were established, as were plots in continuous management of native grasses or sorghum-sudangrass [Sorghum bicolor (L.) Moench nothossp. drummondii (Steud.) de Wet ex Davidse]. Greenhouse gas fluxes were monitored throughout each growing season from 2004 through 2007. Fluxes of N2O were significantly correlated with soil temperature (P < 0.001), and thus a temperature (Q10) correction was made (3.48 for N2O). Nitrous oxide emissions from corn were lowest from the precision tillage treatment (2.4 kg N ha−1 yr−1), significantly lower than the conventional tillage (4.9 kg N ha−1 yr−1) or cover crop corn treatments (5.0 kg N ha−1 yr−1). Corn–soybean and biomass-based cropping systems resulted in significantly greater N2O emissions than native grasses. There was a positive correlation between the N fertilization rate and N2O emissions when comparing all treatments in this study. These soils were typically a sink for atmospheric CH4 for these cropping systems, and thus N2O is the primary non-CO2 GHGs of concern. When evaluating the entire cropping system, native grasses resulted in the lowest N2O emissions, while a corn–soybean rotation planted with precision tillage resulted in N2O emissions similar to bare soil and were significantly lower than emissions from the other cropping systems assessed.