|Dugas, William - TEXAS AG. EXP. STATION|
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 5, 1996
Publication Date: N/A
Interpretive Summary: The increase in the carbon dioxide in the atmosphere has attracted interest due to potential global warming and the prospects of using the soil as storage for carbon released by other 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. This work examined two widely different techniques to measure the carbon dioxide flow from the soil surface of three different cropping systems after tillage. The carbon dioxide released from the three different cropping systems varied depending on the amount of soil carbon that had accumulated. A long-term bermudagrass sod released more carbon dioxide than a conventional tilled system that was already low in organic matter. Within each of the cropping gsystems, the most intense tillage method released the most carbon dioxide relative to an area not tilled. Each measurement technique has its own advantages and disadvantages related to the research objectives. This information will impact scientists around the world by allowing them to use the technique of choice based on the research objectives. These results illustrate the importance of improved conservation tillage systems with less soil disruption to maximize the retention of the soil carbon and minimize the impact on global climate change. These results are significant to farmers and policy makers because intensive tillage results in a substantial short-term gaseous loss of carbon dioxide. 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: Information is needed on the magnitude of CO2 flux and nitrogen transformation caused by tillage in different cropping systems. The objective of this work was to measure the effects of tillage on short- term CO2 flux and nitrogen transformation from three cropping systems on a Houston Black clay. The cropping systems included a four-year no-till sorghum, a 30-year Coastal bermudagrass sod, and a 30-year conventional tilled sorghum. The two primary tillage methods were moldboard and chisel plow, each followed five hours later with two passes of a disk harrow. The CO2 flux was measured using a soil chamber (10**-3 m**3) and a canopy chamber (3.2 m**3) for 24 hours. The largest flux (12.5 mg CO2 m**-2 s**-1) occurred immediately after chisel plow on the bermudagrass. Cumulative CO2 fluxes after tillage with the canopy chamber were highest on bermudagrass and lowest on conventional-tilled sorghum. The soil chamber and canopy chamber showed similar qualitative temporal and treatment trends. There was no clear relationship between N transformations and CO2 flux, suggesting initial high CO2 fluxes are not microbially controlled.