ABSTRACT
Loss of soil carbon during the past 150 years has depleted many of the most productive soils and resulted in degradation of marginal soils upon which many depend. The potential to restore carbon stocks in different landscapes through careful land management practices could result in significant improvements to crop production in agricultural lands and overall soil quality improvements in other lands (Lal, 2004; IPCC, 2000). Increases in soil organic carbon (SOC) depend on climate and management practices, and potential increases are estimated from 0 to 150 kg C·ha-1 per year in semiarid environments up to 1,000 kg C·ha-1 per year in more humid environments (Lal, 2004; Armstrong et al., 2003; West and Post, 2002). Current methods of carbon analysis (e.g., Rossel et al., 2001; Scharpenseel et al., 2001) provide the analytical tools needed to estimate these increases in the SOC pool with some precision. However, advanced analytical methods (e.g., Wielpolski, Chapter 20; Ebinger et al., 2003; McCarty et al., 2002; McCarty and Reeves, 2001; Cremers et al., 2001) offer improved detection, ease of operation, and potential use in the field that could improve precision and accuracy of SOC measurements. In addition, the need for improved accuracy and precision to support national and international policies on carbon emissions and carbon trading may require orders of magnitude more measurements to provide valid support for various positions and land man-
agement practices. These measurements must be delivered at the lowest cost possible and with well-characterized uncertainties. Current methods fall short on cost-effectiveness as well as accuracy and precision; advanced methods, once fully developed and tested, should optimize the amount of information about SOC pools per dollar spent, and must be designed to keep the cost of assessing carbon to less than 10 percent of the total costs of sequestration practices (DOE, 2004). With carbon trading in the United States and Europe creating a commodity market for sequestered carbon, the need to measure and certify increases (or decreases) in SOC within three to five years of implementing carbon sequestration and management practices, and to do so at the lowest levels of detection, is a pressing issue.
