the effect of agricultural practices

on carbon sequestration: INDIANA study

Agricultural cropland in Indiana, including both mineral and organic soils, is currently sequestering about 0.77 million metric tons of carbon (MMTC) per year, according to a 2002 study led by Phil Smith, USDA Natural Resources Conservation Service (NRCS) Information Technology Center in Ft. Collins, Colorado. This is equivalent to 2.8 MMT of CO2 per year.

Also cooperating in this study were John Brenner, USDA-NRCS cooperating scientist at the Colorado State University Natural Resource Ecology Lab (CSU NREL); Keith Paustian, Kendrick Killian, Mark Easter, Jan Cipra, and Steve Williams, CSU NREL; Jill Schuler, USDA-NRCS; George Bluhm, NRCS (retired); and Ted Elliott, University of Nebraska (deceased). The study was based on a computer simulation model called CENTURY.

In Indiana, the cultivation of mineral soils actually sequesters an estimated 1.23 MMTC per year, according to 1999 figures. But this is offset significantly by the release of C from the cultivation of the organic soils in far northern Indiana. The cultivation of organic soils releases about 0.55 MMTC per year into the atmosphere.

This overall net sequestration of 0.77 MMTC per year from agricultural cropland is equivalent to an offset of about 2.7 percent of Indiana’s annual fossil fuel carbon emissions, based on 1999 emissions estimates by the EPA of 59.85 MMTCE per year.

More C is being sequestered in the soils in the northern part of the state than in the southern part. This reflects the greater amount of cultivated cropland on mineral soils in the northern part, along with greater adoption of moderate and no-till systems. More grass conservation practices are also installed in the northern part of Indiana.

The principal management trends affecting soil C sequestration are the adoption of moderate tillage and no-tillage systems (compared to intensive tillage), and the introduction of the Conservation Reserve Program (CRP). On the average, the model used by the scientists projects that adoption of no-till in a corn-soybean rotation in Indiana increases soil C by 0.20 tons per acre per year, and adoption of moderate tillage increases soil C by 0.12 tons per acre per year. In Indiana, conversion of cropland under intensive tillage to CRP increases soil C by 0.4 tons per acre per year over the first 10 years in CRP.

Just less than half of Indiana cropland was still using intensive tillage practices in 1998. Any movement toward more acres of moderate tillage or no-till would potentially result in large increases in C sequestration in agricultural soils in Indiana.

The estimated status of C sequestration on cropland in Indiana, as of 1999, is as follows:

* Intensive tillage on mineral soils, 6.644 million acres, sequesters a total of 0.254 MMTC/year

* Moderate tillage on mineral soils, 5.121 million acres, sequesters a total of 0.787 MMTC/year

* No-tillage on mineral soils, 0.918 million acres, sequesters a total of 0.186 MMTC/year

* Conservation Reserve Program and grass conversion, 0.604 million acres, sequesters a total of 0.217 MMTC/year

* Tree/Wetland conversion, 0.060 million acres, sequesters a total of 0.011 MMTC/year

* Cultivation of organic soils, 0.214 million acres, (releases a total of 0.681 MMTC/year)

Grand Total: 0.77 MMTC sequestered per year

How much good is this doing in terms of offsetting CO2 emissions?

The combustion of 424 U.S. gallons of gasoline will produce 1.0 short ton of C emissions in CO2. One short ton C equals 0.907 MMTC. Since agricultural soils (mineral and organic soils combined) are sequestering 0.77 MMTC per year in Indiana, those soils are removing the equivalent amount of CO2 from the atmosphere that is produced from the combustion of 362 million gallons of gasoline.

In conducting their study, the scientists combined data on soil types (using STATSGO), climate (using PRISM), current management practices being used by producers (using the Carbon Sequestration Rural Appraisal, or CSRA), cropping patterns (using various sources), soil C sequestration rates for various management practices (from long-term agricultural research projects), and other factors, into the CENTURY model to predict carbon sequestration levels in Indiana. Information from CTIC and Indiana Agricultural Statistics Service databases was also used.

The team also developed a Decision Support Tool program that allows producers to find out how changes in management would affect C sequestration on their specific soils. This program is called the Indiana CarbOn Management Evaluation Tool (COMET).

The entire report can be found at: http://www.oznet.ksu.edu/ctec/Brenner's_study/IndianaCarbonStudy/Indiana_Final_Report.pdf

For more information, contact either:

John Brenner jbrenner@nrel.colostate.edu

Keith Paustian keithp@nrel.colostate.edu

-- Steve Watson <swatson@oznet.ksu.edu>