ARS | Publication request: Soil Organic C Stocks with Depth and Land Use at Various US Sites.

Submitted to: Soil Science Society of America Special Publication Book Chapter
Publication Type: Book/Chapter
Publication Acceptance Date: July 17, 2008
Publication Date: N/A

Interpretive Summary: Cropped treatments paired across all soil series with native sites had a mass of SOC present in the top 100 cm that averaged 78% of that found in native sites. These data likely indicate that the farming practices that are presently used do maintain and possibly restore SOC levels in many US soils to nearer their native levels than is reported in the literature. Regardless, cropping has lowered the SOC in the 0- to 10 and to a lesser degree in the 0- to 30 cm depths where the masses of SOC remaining are 59 and 68%, respectively across all cropped sites, compared to the corresponding depths for the native sites. By comparison, the effect of re-vegetation on the mass of SOC present shows a restoration of SOC, particularly at the 0- to 10 and the 0- to 30 cm depths where the masses of SOC averaged 83 and 86 %, respectively of the amounts of native SOC. Within a subset of the data where comparisons could be made the no-till averaged 20,680 kg ha-1 greater mass of SOC within the top 100 cm than did conventional tillage.

Technical Abstract: A total of 21 soil series were sampled across 18 States. The data reported provide a broadly-based set of soil organic carbon (SOC) measurements. Sampling was designed to allow comparisons of individual treatments (native, cropped, or re-vegetated) that were from the same geomorphic unit, mapped series, slope, and aspect. Results were analyzed based upon the differences in masses of SOC with depth among treatments at each site. Compared to corresponding depths for native sites, cropping had lowered the remaining SOC in the 0- to 10 and the 0- to 30 cm depths to 59 and 68 %, respectively. The SOC present in the top 100 cm across all cropped treatments had a mass that averaged 78% of that found in the native sites. A sub-set of sites extending from Ohio, through Indiana, Kansas, Nebraska, and into Idaho were used to determine if no-till resulted in more SOC sequestration in the top one meter depth than did conventional till. The no-till and conventional treatments averaged 134,500 and 113,820 kg SOC ha-1 in the top 100 cm of soil, respectively. This result indicates that no-tillage and likely reduced-tillage treatments result in a larger mass of sequestered SOC to a depth of 100 cm than do conventionally-tilled treatments.