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Title: TOTAL ORGANIC CARBON LOSSES IN SUBSURFACE FLOW UNDER TWO MANAGEMENT PRACTICES

Author
item Owens, Lloyd
item Starr, Gordon
item Lightell, Donald

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Green house gases and global warming have become major, current topics. Much of the green house gas discussion has dealt with carbon dioxide (CO2) and methods to sequester or store atmospheric carbon. To better understand the overall process, the entire carbon cycle needs to be studied. The major carbon transformations are loss of CO2 to the atmosphere or the storage of carbon in sinks such as soil. Although it is a minor pathway, carbon losses leaching through the soil and into groundwater need to be quantified. In this study water from developed springs and water coming out of the bottom of large soil blocks (called lysimeters) were analyzed for Total Organic Carbon (TOC). Concentrations of TOC in these water samples were low (1 to 3 ppm) and were similar with a corn/soybean rotation and with pastures. The annual loss of TOC ranged from 3.1 to 4.9 lb/ac. The research is relevant to other scientists and policy makers who need more scientifically sound information upon which to base decisions about carbon credits.

Technical Abstract: Although there has been much study of various aspects of the carbon cycle, concentrations and losses of Total Organic Carbon (TOC) moving through a soil profile have received little attention. Therefore, the purpose of this study was to assess TOC levels in lysimeter percolate and groundwater. TOC was determined monthly in the percolate from large lysimeters (2.4 m deep [8 ft]) with undisturbed soils under row crops with a chisel-plow tillage treatment. Although there is some variability in the TOC concentrations in the percolate, most of the TOC values were in a range of 0.5 - 6.0 mg/lL with the corn/soybean-rye rotation. Developed springs in two rotational grazing systems (fertilized grass and a grass-legume mixture) were sample for 10 years. TOC concentrations in the groundwater from the spring developments had less variability than in the lysimeter percolate. Most TOC values from these pasture systems were in a concentration range of 1 to 3 mg/L. Annual averages of TOC transport were similar for the lysimeter percolate and groundwater springs, ranging from 3.5 to 5.5 kg/ha (3.1 to 4.9 lb/ac).