State Level Assessments of Carbon Sequestration

Soils in mid-Western states have large C sequestration potential.

Land managers have long known the importance of soil organic matter in maintaining the productivity and sustainability of agricultural land. More recently, interest has developed in the potential for using agricultural soils to sequester C and mitigate increasing atmospheric CO2 by adopting practices that increase standing stocks of carbon in soil organic matter and vegetation. To help local land owners and land mangers in their decision-making process, we initiated state level assessments in Iowa, Indiana and Nebraska to determine how management decisions involving cropping and tillage systems affect soil organic matter.

Our approach utilized a variety of resource data (on climate, soils, land use and management), long-term field experiment results, and the Century EcoSystem Soil Organic Matter Computer Model developed at Colorado State University. The initial Phase I studies of cropland in the states used existing information on climate, soils and management factors (e.g., drainage, irrigation, crops grown, production levels and tillage systems) to estimate current rates of C sequestration. From these early studies, we found that individual counties had land use information, including management histories of crop rotations and tillage practices, drainage histories, irrigation histories, fertilizer rates, and conservation practices that were not available in published databases. This information is very important in determining the C sequestration rates within a state.

To capture this information and utilize it in the state level C assessments, a Phase II study was done that involved all 284 counties. To communicate with the local land managers and collect the local data, a new survey instrument called the Carbon Sequestration Rural Appraisal (CSRA) survey instrument was developed, tested and modified. Through the use of geographic information systems (GIS) and existing databases of land use and soil types, individual tailored spreadsheets were prepared for each county detailing existing land use and soils interactions. Local land managers used this information to assess land use changes since the start of cultivation in their area and provided information on cropping systems, tillage systems, fertilizer application rates from manure and commercial sources, irrigation, drainage and the application of conservation practices. This local data provided additional inputs into the Century Model that were not available in previously published databases, and refined the output for the individual counties and the soils and crop/tillage systems. Century Model estimates for multiple scenarios are now available in the Carbon Management Evaluation Tool (COMET) databases for each state.

Final assessments suggest that agricultural soils are currently sequestering 11 billion lbs of C per year in these three states (equivalent to 42 billion lbs of CO2 per year), largely through increased adoption of conservation practices over the past 10 to 20 years. It is also apparent that agricultural soils have the potential to sequester even larger amounts of C, should land managers make C conserving decisions.

John Brenner, USDA-NRCS, and
Keith Paustian, Professor
Soil & Crop Sciences
Natural Resources Ecology Lab

FROM THE GROUND UP agronomy news is a monthly publication of Cooperative Extension, Department of Soil & Crop Sciences, Colorado State University, Fort Collins, Colorado. Web Site: http://www.colostate.edu/Depts/SoilCrop/extension/Newsletters/news.html The information in this newsletter is not copyrighted and may be distributed freely. Please give the original author the appropriate credit for their work.
Jessica Davis, Technical Editor Direct questions and comments to: Deborah Fields Phone: 970- 491-6201 Fax: 970-491-2758 e-mail: dfields@lamar.colostate.edu	Extension staff members are: Troy Bauder, Water Quality Mark Brick, Bean Production Joe Brummer, Forages Betsy Buffington, Pesticide Pat Byrne, Biotechnology Jessica Davis, Soils Jerry Johnson, Variety Testing Raj Khosla, Precision Farming Sandra McDonald, Pesticide Calvin Pearson, New Crops James Self, Soil, Water, & Plant Testing Reagan Waskom, Water Resources