2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 9
Presentation Time: 8:00 AM-6:00 PM

C Balance and Growing Season GHG Emissions from Corn-Soybean Rotations on a Midwestern Mollisol (Gracenet Project)


STOTT, Diane E., SMITH, Douglas R. and BUCHOLTZ, Dennis, National Soil Erosion Research Laboratory, USDA-ARS, 275 S RUSSELL STREET, West Lafayette, IN 47907, Diane.Stott@ars.usda.gov

Changes in management can reduce agriculture contributions to greenhouse gases (GHG). A field study was started in 2003 on a Typic Haplaquoll to determine the impact of tillage and N management on GHG emissions. There were four treatments for a corn-soybean rotation implemented: 1) chisel/disk tillage with N fertilizer applied as urea ammonium nitrate (UAN) before planting corn; 2) No-till with pre-plant UAN; 3) No-till with split application of UAN; and 4) No-till with winter rye as a cover crop with pre-plant UAN. There were four replicates, with corn and soybean phases planted each year. Starting in 2004, CO2, CH4 and N2O emissions were measured throughout the growing season. CO2 emissions in corn peaked in late June, and were significantly higher in the CD and cover crop system, while there was no difference between the no-till systems. For soybeans, CO2 emissions peaked in late July, with the cover crop producing more than the other systems some years. Overall emissions during the growing seasons were higher in soybean than in corn, 20.7 and 14.4 Mg CO2 ha-1 yr-1, respectively. The soil served as a sink for CH4, with a mean of 11.6 kg CO2 equivalents ha-1 yr-1 sequestered, with no difference between crops or within crops. N2O emissions peaked in corn about a month after fertilizer application. There were no differences between corn and soybean, and the amounts emitted were trivial compared to the CO2 emissions (a mean of 0.2 kg CO2 equivalents emitted as N2O). Overall mean global warning potential was higher for soybean than for corn, 5.1 and 2.4 Mg CO2 equivalents emitted, respectively. C balance and fuel usage analysis will be presented. CO2 emissions are reduced due to fewer tillage operations, so that implementing no-till can immediately reduce CO2 emissions, despite lack of differences in the field.