Submitted to: Soil & Tillage Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/27/2005
Publication Date: 10/6/2006
Citation: Bauer, P.J., Frederick, J.R., Novak, J.M., Hunt, P.G. 2006. Soil CO2 flux from a norfolk loamy sand after 25 years of conventional and conservation tillage. Soil & Tillage Research. 90:205-211. Interpretive Summary: Many southeastern USA soils have low productivity because they do not hold water or nutrients very well. Increasing the amount of organic matter in the soil may increase productivity. We studied the loss of organic carbon from the soil as carbon dioxide to the atmosphere from soil that has been in conventional tillage or conservation tillage for over 25 years and tried to relate the carbon dioxide losses to the atmosphere to soil physical and chemical properties. We found that carbon dioxide losses were much greater for conventional tillage than for conservation tillage, especially after a rainfall when the soils were moist. We also found that carbon dioxide losses in conventional tillage did not differ greatly within a season, but that loss rates were highest in the summer and lowest in the fall (summer, spring, and fall were evaluated). We did not find a good relationship between carbon dioxide flux rates and any of the soil and chemical properties we measured. This information will be useful to scientists developing soil management systems that increase soil organic matter.
Technical Abstract: Increasing soil C on coarse-textured soils of the southeast USA appears one avenue to help maintain sustainability of crop production in the region. Information on C losses from these soils may aid in designing improved management systems. Our objective was to compare conventional to conservation tillage for soil CO2 flux. A second objective was to determine whether soil physical or chemical properties within each tillage system were related to CO2 flux rates on these soils. Data were collected from an experiment on a Norfolk loamy sand soil that was established in 1978. Data were collected over several weeks during June and July in 2003, October and November in 2003, April in 2004, and May, June, and July in 2004. Soil CO2 flux rates in conventional tillage were greater than those in conservation tillage at most of the measurement times in each season. Water content of surface soil layer (6.5 cm) was almost always higher in conservation tillage than in conventional. Soil CO2 flux was highly dependant on soil water content only in conventional tillage. Flux rates in conservation tillage averaged 0.84 g CO2/sq m/hr in the summer of 2003, 0.36 g CO2/sq m/hr in the fall of 2003, 0.46 g CO2/sq m/hr in the spring of 2004, and 0.86 g CO2/sq m/hr in the summer of 2004. In conservation tillage, no significant correlations occurred between soil CO2 flux and soil N, C, C:N ratio, pH, bulk density, sand fraction, or clay fraction of the surface 7.5 cm. In conventional tillage, sand fraction was positively correlated while bulk density and clay fraction were negatively correlated with soil CO2 flux rate only when the soil was moist. Since only small differences occurred within seasons in this study for soil CO2 flux rate, it appears that efforts to enhance carbon sequestration with conservation tillage on these sandy soils need to focus on the quantity and composition of the residues added to the soil.