Author
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Reicosky, Donald |
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Submitted to: Proceedings of Carbon Sequestration in Soils Conference
Publication Type: Proceedings Publication Acceptance Date: 7/23/1999 Publication Date: N/A Citation: 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 intensive 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 short-term gaseous loss of carbon immediately after tillage that partially explains carbon loss from soils. This work evaluated long-term effects (3 months) of moldboard plowing and no-till on carbon dioxide loss from a Barnes loam in west central Minnesota, USA. The initial flush of carbon dioxide immediately after moldboard plowing was nearly 100 times that from the not tilled treatment and declined rapidly during the first four hours. For the 85-day period following tillage, the cumulative carbon dioxide loss from the plowed treatment was 2.4 times higher than that from not tilled. The decline in soil carbon dioxide concentration on the moldboard plow treatment was more dramatic than on the not tilled treatment suggesting that higher soil air permeability in the tilled layer resulted in the higher gas exchange. This information will impact scientists around the world by allowing them to use the technique of choice for measuring carbon loss based on the research objectives. These results are significant to farmers and policy makers because intensive tillage results in a substantial short- and long-term 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: The possibility of global greenhouse warming due to rapid increase in carbon dioxide (CO2) is receiving attention. Agriculture's role in sequestering carbon is not clearly understood. Recent studies have shown that a large short-term pulse of CO2 was released immediately following tillage partially explains C loss from soils. The objective of this work was to evaluate the long-term effects (3 months) of moldboard plowing on CO2 loss from a Barnes loam (Udic Haploborolls, fine-loamy, mixed) in west central Minnesota, USA. Tillage-induced CO2 loss was measured using a large portable chamber for eighty-seven days. The soil CO2 concentration was measured at 5, 10, 20, 30, 50 and 70-cm depths in the no-till plots and 30, 50 and 70-cm depths in plowed plots. Soil gas samples were taken once or twice weekly throughout the growing season from stainless steel mesh sampling tubes. The initial flush of CO2 immediately after moldboard plowing was nearly 100 g CO2 m**-2 h**-1 while that from the not tilled treatment was less than 0.9 g CO2 m**-2 h**-1. For the 85-day period following tillage, the cumulative CO2 flux from the plowed treatment was 2.4 times higher that from not tilled. Both treatments showed a seasonal trend as soil temperature cooled and fluctuations associated with rainfall events. Carbon dioxide concentrations were highest at the 30, 50, 70-cm depths. The decline in soil CO2 concentration on the moldboard plow treatment was more dramatic than on the not tilled treatment suggesting that higher air permeability in the tilled layer resulted in the higher gas exchange. The large differences in CO2 loss between moldboard plow and not-tilled treatments reflect the need for improved soil management and conservation policies to enable carbon sequestration. |
