Author
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Reicosky, Donald |
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Submitted to: International Soil Tillage Research Organization Proceedings
Publication Type: Proceedings Publication Acceptance Date: 7/7/2000 Publication Date: N/A Citation: N/A Interpretive Summary: The increase in carbon dioxide in the atmosphere related to concerns about potential global warming and prospects of using soil as a sink for carbon has attracted interest. The cumulative effect of tillage and many cropping rotations has been a 30-50% decrease in soil carbon that causes undesirable changes in soil physical, chemical and biological properties. Recent studies involving tillage methods indicate major gaseous loss of carbon immediately after tillage. This work evaluates the impact of wind on tillage-induced CO2 loss and both short- and long-term effects of tillage-induced changes in soil properties on CO2 loss. The goal was to evaluate effects of moldboard plowing on soil properties and long-term CO2 loss and to independently verify tillage-induced CO2 loss without the portable chamber. Information on CO2 loss from the soil without using the portable chamber was collected to characterize the plume of CO2 from a plowed strip by measuring the up and downwind concentrations to confirm carbon loss. Intensive tillage results in substantial short-term gaseous losses of CO2. This information will assist scientists and engineers in developing improved tillage methods to minimize the gaseous loss and to improve soil carbon management. 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 be of direct benefit to the farmers to enable them to maintain crop production with minimal impact on air quality and the environment. Technical Abstract: Agricultural ecosystems can play a significant role in the production and consumption of greenhouse gases. Information is needed on the mechanisms and methods of measurement of greenhouse gas emissions from agricultural soils. The objective of this work was to evaluate both short- and long-term effects of tillage-induced changes in soil properties on CO2 loss. The soil lwas a Barnes loam (Udic Haploborolls, fine-loamy, mixed) in west central Minnesota, USA. Information was collected on CO2 loss from the soil by measuring the concentration up and downwind without the chamber to characterize the plume of CO2 from a 5.5 m-wide plowed strip perpendicular to the prevailing wind. Soil gas samples were taken once or twice weekly throughout the growing season from stainless steel mesh sampling tubes. In the first study, downwind-upwind CO2 concentration differences were large immediately after tillage and decreased with time verifying the tillage- induced loss without the chamber. For the 85-day period following tillage in 1998, the cumulative CO2 flux from the plowed treatment was 2.4 times higher that from not tilled. The abrupt change in soil properties caused a decline in soil CO2 concentration on the moldboard plow treatment was more dramatic than on the not tilled treatment suggesting that moldboard plowing created higher soil air permeability in the tilled layer that resulted in the higher gas exchange. The tillage-induced change in soil properties led to short-term losses that were higher than the undisturbed soil for up to three months. The large differences in CO2 loss between moldboard plow and not-tilled treatments reflect the need for improved soil management and policies that favor conservation tillage to enable carbon (C) sequestration in agricultural production systems. |
