|Daigh, Aaron -|
|Horton, Robert -|
|Xiao, Xinhua -|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 30, 2014
Publication Date: N/A
Interpretive Summary: Climate change is linked to the greenhouse effect where certain gases in the atmosphere lead to global warming. One of these greenhouse gases is carbon dioxide, CO2. Carbon dioxide is released from agricultural soils where it is generated by roots and microbes growing in the soil. How much CO2 is released depends on many factors but mainly on the type of organic material in the soil, soil temperature, and soil water content. This experiment measured the amount of CO2 released from the soil for different crops that may be used in bioenergy production. Chambers and analyzers on the soil surface were used to measure the CO2 being released. The chambers were placed in different positions to test whether wheel traffic and/or nitrogen fertilization affect CO2 release. CO2 release was found to be different for different locations within the same crop. The rate of CO2 release was also affected by rainfall with the relationship with temperature changing with soil moisture conditions. High rates of CO2 release were found in prairies and this was thought due to much higher amount of roots as compared to corn and soybean. This research is important to researchers, managers, and growers interested in greenhouse gas production in bioenergy cropping systems.
Technical Abstract: Soil-surface CO2 efflux is a major export of carbon from the soil system. The interest in bioenergy cropping systems has raised questions as to the potential of management strategies to deteriorate soil carbon pools and soil quality. The objective of this research was to evaluate dynamic soil-surface CO2 effluxes of selected annual- and perennial-biofuel cropping systems. Cropping systems evaluated included continuous corn (harvested for both grain and ~ 50% of the corn stover) with and without a winter rye cover crop, mixed prairies (harvested annually for aboveground biomass) with and without nitrogen fertilization, and corn-soybean rotations harvested only for grain. Soil-surface CO2 effluxes, soil temperature, and volumetric soil water contents were monitored weekly from 2008 to 2011 and monitored hourly during periods of 2011. In regards to spatial variability, soil-surface CO2 effluxes significantly varied among intra-crop management zones only for continuous corn rotations with stover removal. However, the incorporation of a winter rye cover crop reduced how often this spatial variability was observed by 70 percent. Residue harvest induced spatial variability of effluxes was not explained by soil physical properties or conditions. In regards to temporal variability, an important finding of this study was the effect of soil water redistribution on diurnal soil-surface CO2 efflux. During apparent soil water redistribution, diurnal trends in soil-surface CO2 effluxes associated with diurnal soil temperature fluctuations was not observed. In general, annual cumulative soil-surface CO2 effluxes were greater in prairies than that of row crops but are attributed to greater quantities of autotrophic soil respiration.