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Rapid Assessment of U.S. Soil Carbon (RaCA)

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Methodology and Summary Reports
Data Tables
Recommended Data Citation
More Data and Information
Questions About the Project

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Rapid Carbon Assessment Values mapped using SSURGO and NLCD grids.


The Rapid Assessment of U.S. Soil Carbon (RaCA) was initiated by the USDA-NRCS Soil Science Division in 2010 with the following objectives:

  • To develop statistically reliable quantitative estimates of amounts and distribution of carbon stocks for U.S. soils under various land covers and to the extent possible, differing agricultural management.
  • To provide data to support model simulations of soil carbon change related to land use change, agricultural management, conservation practices, and climate change.
  • To provide a scientifically and statistically defensible inventory of soil carbon stocks for the U.S.
Soil sample being analyzed for visible-near infrared spectrometry with a muglight device.

To accomplish these objectives, 144,833 samples were collected from the upper 1 meter of 32,084 soil profiles at 6,017 randomly selected locations for measurement of organic and inorganic carbon by visible and near infrared (VNIR) spectroscopy and bulk density by traditional methods. NRI sites were used as the basis for random selection of sample sites stratified by soil group within RaCA Region and land use/land cover (LULC) within soil group. Soil morphology and landscape characteristics were described at each site and limited vegetation and agricultural management information was collected from each location. Sample collection and analysis involved more than 300 soil scientists and assistance from 24 universities.

Methodology and Summary Reports

Rapid Carbon Assessment (RaCA) Methodology (PDF; 1.9 MB)

Summary of Soil Carbon Stocks for Conterminous U.S. (PDF; 1.3 MB)

Data Gathering Documentation

Data Tables

RaCA Site Soil Organic Carbon Stocks (CSV; 0.97 MB)
Metadata (TXT; 2 KB)

Effort has been made to provide accurate and complete information. However, we cannot guarantee that there will be no errors. It is the user’s responsibility to understand the prediction methods and uncertainties that are associated with this data. Neither the U.S. Government, USDA, NRCS, or NSSC assumes any legal liability for the accuracy, completeness, or usefulness of any information, product, or process disclosed herein.

Values for Each Rapid Carbon Assessment Site.


Soil Organic Carbon Stocks

Rapid Carbon Assessment Values Using SSURGO and NLCD Grids (PDF; 1.54 MB)
Geometric Means for Each RaCA Region (PDF; 766 KB)
Values for Each RaCA Site (PDF; 1.05 MB)

RaCA Regions


University of Alaska

University of Idaho

Oregon State

Tuskegee University

University of Arkansas – Fayetteville

Idaho State University

Penn State University

Utah State University

University of Arkansas – Pine Bluff

Louisiana State University

Purdue University

West Virginia University

Auburn University

University of Missouri

University of Rhode Island

University of Wisconsin

Colorado State University

University of Nebraska – Lincoln

University of Tennessee – Martin

University of Wisconsin – Stevens Point

University of Florida

University of Nevada – Reno

Tennessee Tech University


University of Hawaii

North Carolina State University

Texas A&M (AgriLife)


Recommended Data Citation

Soil Survey Staff. Rapid Assessment of U.S. Soil Carbon (RaCA) project. United States Department of Agriculture, Natural Resources Conservation Service. Available online. June 1, 2013 (FY2013 official release).

More Data and Information

Questions About the Project

Contact the Soils Hotline Staff

Phone: Steve Speidel at 402-437-5378 or Tammy Cheever at 402-437-5379

Soil sampling crew on a snowy forest trail.