Author
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Reicosky, Donald |
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Submitted to: Crop Simulation Workshop Abstracts
Publication Type: Abstract Only Publication Acceptance Date: 4/11/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: The cumulative effect of tillage and many cropping rotations has been an undesirable change in soil physical, chemical and biological properties primarily as a result of a decrease in soil C. Recent studies involving tillage methods show gaseous loss of C immediately after intensive tillage. Differences in the CO2 loss as a result of tillage methods were related to soil fracturing that facilitated movement of CO2 out of the soil and O2 into the soil. The moldboard plow left the soil in a rough, loose and open condition that resulted in the maximum CO2 loss relative to areas not tilled. These results were obtained using a large portable canopy chamber with turbulent mixing. The concern about turbulent mixing and how it might impact soil gas fluxes from tilled surfaces led to work evaluating fluxes after tillage measured with a small soil chamber and the large portable canopy chamber. The CO2 flux measured by both methods was maximum immediately after tillage, but the maximum soil chamber fluxes were only about 10% of those measured by the canopy chamber. The large differences between the two chambers are likely related to the small diameter of the soil chamber that precluded a representative measurement and to increased turbulence inside the canopy chamber and associated pressure effects. Fluxes from surfaces not tilled were similar for both chambers. Tillage- induced differences in soil porosity and air permeability may be related to the large flux measured with the canopy chamber. The pressure and wind speed under the portable canopy chamber at the soil surface were measured and showed a net negative pressure (-1.5 Pascal). The results suggest a need for a model to describe the tillage-induced flux and how the air flow inside the chamber is different from that in the open field. |
