Author
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Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/12/2016 Publication Date: 5/25/2016 Citation: Lehman, R.M., Osborne, S.L. 2016. Soil greenhouse gas emissions and carbon dynamics of a no-till, corn-based cellulosic ethanol production system. BioEnergy Research. doi: 10.1007/s12155-016-9754-y. Interpretive Summary: Crop residues like corn stover perform important functions that promote soil health and provide ecosystem services that influence agricultural sustainability and global biogeochemical cycles. Corn stover harvesting for livestock feed, bedding, and cellulosic ethanol production has been rising and is expected to increase in the future. In a four-year study, we evaluated the effect of corn residue removal from a no-till, corn-soybean rotation on crop yields, greenhouse gas (GHG; CO2, N2O, CH4) fluxes, and net global warming potential. Yields for either corn or soybean were not significantly affected by residue removal. Residue removal did not significantly affect GHG fluxes from corn; however, significantly higher (107%) N2O fluxes were observed in soybean with residue removal compared to control plots. All field plots were a net source of CH4 during this period (2009 – 2012). Soil organic carbon (SOC) increased in both treatments during the four-year study with a lower rate of SOC accumulation with corn residue removal compared to plots without residue removal. Because of the net gain in SOC in all plots, net global warming potential was negative for both treatments. This finding indicates that under local soil-climatic conditions, no-till practices can permit biennial corn stover harvesting while not increasing global warming potential. However, our results also show that repeated corn residue harvesting may increase nitrogen loss from fields as N2O. These data fill specific knowledge gaps for life cycle analyses of regional bioenergy cropping systems. Technical Abstract: Crop residues like corn 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 residue removal from a no-till, corn-soybean rotation on greenhouse gas (GHG; CO2, N2O, CH4) fluxes, crop yields, greenhouse gas intensities, and net global warming potential (GWP). We conducted a four-yr study using replicated field plots in a randomized complete block design that had been managed with two levels of residue removal (none, baled stover) for four complete crop cycles prior to initiation of ground surface gas flux measurements. Yields for either corn or soybean were not significantly affected by residue removal with yields across all plots averaging 7.28 Mg ha-1 for corn and 2.64 Mg ha-1 for soybean. Residue treatment did not significantly affect GHG fluxes from corn; however, significantly higher (107%) N2O fluxes were observed in soybean with residue removal compared to control plots. Although there was no significant residue treatment effect on CH4 flux, these plots were a net source of CH4 (0.54 kg CH4-C ha-1 yr-1). Soil carbon increased in both treatments during the four-year study with a lower rate of SOC (0-30 cm) accumulation with residue removal (497 kg C ha-1 yr-1) compared to control plots (538 kg C ha-1 yr -1). Estimated net annual GWP was -694 kg CO2-eq ha-1 yr-1 for the control plots and -472 kg CO2-eq ha-1 yr-1 for the residue removal plots indicating under local soil-climatic conditions, no-till practices can permit biennial corn stover harvesting and still maintain a negative GWP. Our results also show that repeated corn residue harvesting may increase nitrogen loss from fields as N2O which represents a negative contribution of overall global warming potential within agricultural production systems. These data fill specific knowledge gaps for life cycle analysis of regional bioenergy cropping systems. |
