Soil Greenhouse Gas Emissions and Carbon Dynamics of a No-Till, Corn-Based Cellulosic Ethanol Production System
2016
Lehman, R Michael | Osborne, Shannon L.
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.
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