Author
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Reicosky, Donald |
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Submitted to: Soil Source and Sink of Greenhouse Gases
Publication Type: Proceedings Publication Acceptance Date: 5/11/1996 Publication Date: N/A Citation: N/A Interpretive Summary: The increase in the carbon dioxide in the atmosphere has attracted interest due to the concerns about potential global warming and the prospects of using soil as a sink for carbon released by human activity. The cumulative effect of tillage and many cropping rotations has been a 30-50% decrease in soil carbon that causes an undesirable change in soil physical, ,chemical and biological properties. Recent studies involving tillage methods indicate major gaseous loss of carbon immediately after tillage. Differences in the CO2 losses as a result of tillage methods were related to soil fracturing that facilitated movement of carbon dioxide out of and oxygen into the soil. The moldboard plow left very nearly all of the soil in a rough, loose and open condition, that resulted in the maximum CO2 loss. Conservation tillage tools that leave more residue on the surface had only 31% of the CO2 loss caused by the moldboard plow. Progress is being made in developing conservation tillage tools that can further enhance soil carbon management. These results are significant to farmers and policy makers in that tillage results in substantial short-term gaseous losses of CO2. Farmers can develop and utilize new management techniques for enhancing soil carbon by increasing the quantity and quality of crop residues and by changing the type and intensity of tillage. This information will assist scientists and engineers to develop improved methods of tillage to minimize the gaseous loss and improve soil carbon management. This information will be of direct benefit to the farmers to enable them to maintain crop production with minimal impact on the environment. Technical Abstract: The influence of agricultural production systems on greenhouse gas generation and emission is of interest as it may affect potential global climate change. Information is needed on the mechanism and magnitude of gas generation and emission from agricultural soils with specific emphasis on tillage mechanisms. This work evaluated four different tillage methods on the short-term CO2 and water vapor flux from a clay loam soil in the Northern Cornbelt of the U.S.A. The four tillage methods were moldboard plow only, moldboard plow plus disk harrow twice, disk harrow and chisel plow using standard tillage equipment following a wheat (T. Aestivum L) crop compared with no tillage. The CO2 flux was measured with a large portable chamber commonly used to measure crop canopy gas exchange. The moldboard plow treatment buried nearly all of the residue and left the soil in a rough, loose, open condition and resulted in maximum CO2 loss. The carbon released as CO2 during the 19 days following the moldboard plow, moldboard plow plus disk harrow, disk harrow, chisel plow and not tilled treatments would account for 134%, 70%, 58%, 54% and 27% respectively of the carbon in the current year's crop residue. Carbon dioxide losses 5 hours after four conservation tillage tools were only 31% of that of the moldboard plow. The moldboard plow lost 13.8 times as much CO2 as the soil area not tilled, while different conservation tillage tools lost only 4.3 times. Conservation tillage reduces the extent, frequency and magnitude of mechanical disturbance caused by the moldboard plow and reduces the air- filled macropores and slows the rate of carbon oxidation. Any effort to decrease tillage intensity and maximize residue return should result in carbon sequestration for enhanced environmental quality. |
