Thomas Sauer and Douglas Karlen, USDA-ARS National Laboratory for Agriculture & the Environment, Ames, IA
Corn stover has been identified as a potential cellulosic ethanol feedstock prompting assessments of the effects of residue removal on soil processes. The objective of this study was to determine the effect or corn residue removal on carbon dioxide (CO2) and nitrous oxide (N2O) fluxes from soil. A replicated field trial of continuous corn (Zea mays L.) production was established in 2007 on Endoaquoll and Hapludoll soils near Ames, IA. Treatments included 0, 50, and 100% surface residue removal from corn under chisel plow, no-tillage, and chisel plow with biochar application. Soil CO2 flux was measured at one PVC collar (0.031 m2 area) inserted into the soil at in-row and between-row positions in each plot using a Li-Cor LI-8100 infrared CO2 analyzer. Soil N2O flux was measured by collecting gas samples beneath closed covers on the same collars followed by sample analysis using gas chromatography. Hourly soil water content and temperature were measured with Decagon 5TM or EC-TM sensors and EM50R dataloggers. Increasing amount of residue removal often, but not always, produced progressively decreasing soil CO2 fluxes. Biochar application also had mixed effects on CO2 fluxes. Fluxes of N2O were dominated by high values following a sidedress application of 32% UAN at 180 kg ha-1 rate and with Agrotain urease inhibitor. The measured N2O fluxes had an average global warming potential (GWP) equivalent to 28% of the CO2 fluxes.