Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2011
Publication Date: 11/1/2011
Citation: Kaspar, T.C., Parkin, T.B. 2011. Soil CO2 flux in response to wheel traffic in a no-till system. Soil Science Society of America Journal. 75:2296-2304. Interpretive Summary: Increasing carbon dioxide concentrations in the atmosphere may be contributing to climate change. One way to reduce the amount of carbon dioxide in the atmosphere is to store more carbon in our agricultural soils. Scientists can measure the carbon storing potential of farming practices, like no-till, by measuring the amount of carbon dioxide that comes out of the soil. Scientists, however need to understand the soil and weather factors that affect the amount of carbon dioxide coming from the soil to choose the best farming practices. The objective of our study was to evaluate the effect of compaction from farm machinery and soil wetness on carbon dioxide flux. Compaction from farm machinery decreased carbon dioxide loss from the soil surface. Soil wetness also reduced carbon dioxide loss, but the effect of compaction was greater. These results are important to scientists because they will need to consider soil compaction when making their measurements and comparing the carbon storing potential of different practices. The results are important to farmers because they will improve comparisons of the carbon storing potential of farming practices, which will allow farmers to make better decisions to improve their soil productivity and reduce carbon dioxide concentrations in the atmosphere.
Technical Abstract: Measurements of soil CO2 flux in the absence of living plants can be used to evaluate the effectiveness of soil management practices for C sequestration, but field CO2 flux is spatially variable and may be affected by soil compaction and percentage of total pore space filled with water (%WFPS). The objectives of our study were: 1) to evaluate the effect of wheel traffic compaction on CO2 flux at two landscape positions with differing soil properties and 2) to examine the relationship of CO2 flux and %WFPS under field conditions and a wide range of soil porosities. Carbon dioxide flux was measured near Ames, IA in a no-till system without living plants using the closed chamber method on nine cylinders inserted into the soil and evenly spaced across three rows, an untracked interrow, and a tracked interrow. Flux, volumetric water contents, and soil temperature were measured on 12 or 13 days between day of year (DOY) 164 and 284 in 2001, 2004, and 2005. Bulk density, soil C concentration, and soil texture were determined after DOY284. On most days, CO2 flux was less in the tracked interrow than in the row or untracked interrow positions. In all three years, the cumulative flux of the tracked position was significantly less than one or both of the other positions. Landscape position did not affect the response of CO2 flux to traffic. There was no evidence that %WFPS was the dominant factor controlling CO2 flux. Compaction from wheel traffic should be considered when soil CO2 flux is used compare management practices.