Soil Greenhouse Gas Emissions and Carbon Dynamics of a No-Till, Corn-Based Cellulosic Ethanol Production System
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Crop residues like corn (Zea mays L.) stover perform important functions that promote soil health and provide ecosystem services that influence agricultural sustainability and global biogeochemical cycles. We evaluated the effect of corn stover removal from a no-till, corn-soybean (Glycine max (L.) Merr) rotation on soil greenhouse gas (GHG; CO2, N2O, CH4) fluxes, crop yields, and soil organic carbon (SOC) dynamics. We conducted a 4-year study using replicated field plots managed with two levels of corn stover removal (none; 55 % stover removal) for four complete crop cycles prior to initiation of ground surface gas flux measurements. Corn and soybean yields were not affected by stover removal with yields averaging 7.28 Mg ha−1 for corn and 2.64 Mg ha−1 for soybean. Corn stover removal treatment did not affect soil GHG fluxes from the corn phase; however, the treatment did significantly increase (107 %, P = 0.037) N2O fluxes during the soybean phase. The plots were a net source of CH4 (∼0.5 kg CH4-C ha−1 year−1 average of all treatments and crops) during the generally wet study duration. Soil organic carbon stocks increased in both treatments during the 4-year study (initiated following 8 years of stover removal), with significantly higher SOC accumulation in the control plots compared to plots with corn stover removal (0–15 cm, P = 0.048). Non-CO2 greenhouse gas emissions (945 kg CO2-eq ha−1 year−1) were roughly half of SOC (0–30 cm) gains with corn stover removal (1.841 Mg CO2-eq ha−1 year−1) indicating that no-till practices greatly improve the viability of biennial corn stover harvesting under local soil-climatic conditions. Our results also show that repeated corn stover harvesting may increase N loss (as N2O) from fields and thereby contribute to GHG production and loss of potential plant nutrients.
KeywordsCorn stover Cellulosic ethanol GRACEnet Greenhouse gases Maize (Zea mays L.) Methane Nitrous oxide No-till Soil organic carbon Soybean (Glycine max (L.) Merr)
This research was funded by the USDA-Agricultural Research Service (ARS) as part of the USDA-ARS-REAP (Resilient Economic Agricultural Practices) and GRACEnet projects, with additional funding provided by the North Central Regional Sun Grant Center at South Dakota State University through a grant provided by the US Department of Energy (DOE) – Office of Biomass Programs [now Bioenergy Technology Office (BETO)] under award number DE-FC36-05GO85041. Technical assistance in the field and/or lab is acknowledged from Kurt Dagel, Amy Christie, and Sharon Nichols.
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Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture. USDA is an equal opportunity provider and employer.
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