1. Institute of Atmospheric Sciences South Dakota School of Mines and Technology Potential for soil carbon sink enhancement in 3 northern Great Plains states. Karen Updegraff Patrick R. Zimmerman Donna Kliche Rick Clawges William J. Capehart Patrick Kozak Maribeth Price

2. Institute of Atmospheric Sciences South Dakota School of Mines and Technology Big Sky Regional Partnership: MT, SD, ID ● Phase I assessment of terrestrial potential ● Modeled using CENTURY, GIS ● Agriculture is currently a net C sink ● MT has greatest land base but SD has most cropland ● No-till in SD offers most potential Current:

3. Institute of Atmospheric Sciences South Dakota School of Mines and Technology Climate data ● National Climatic Data Center (NCDC) monthly average precip, min/max temperature since 1895 by station and climate division.

4. Institute of Atmospheric Sciences South Dakota School of Mines and Technology Generation of soil texture grids ● SSURGO/STATSGO map unit data extracted into sand/silt/clay % grids. Bulk density from texture ● ENVI processing to generate soil classes ● Distributed soil classes within counties

5. Institute of Atmospheric Sciences South Dakota School of Mines and Technology Historical and current agricultural management: I ● Historical data from extension survey (SD), NASS crop databases, Census of Agriculture, anecdotal sources (types of crops, fertilizer use, irrigation) ● Conservation tillage and CRP data for 2002 from CTIC. No-till = ZERO tillage ● For point simulations, represent spatial proportions of crops as temporal series ● 6 timeblocks: 1900-35, 1936-45, 1946-65, 1966-82, 1983-89, 1990- ● Assume grassland for baseline period

6. Institute of Atmospheric Sciences South Dakota School of Mines and Technology Historical and current agricultural management: II ● Assume no fertilizer before 1965 ● Assume no irrigation unless >50% of crop was irrigated ● Scenarios – ct2ct: continuous conventional tillage since 1900 – ct2nt: conventional, change to no-till in 1990 – ct2crp: conventional, change to CRP in 1990 – grz2grz: continuous grazing since 1990 – grz2crp: removal of grazing in 1990

7. Institute of Atmospheric Sciences South Dakota School of Mines and Technology Historical and current agricultural management III ● No public lands in simulation ● Runs to 2030 (stochastic weather after 2003) ● For each state: – 8-10 climate divisions – 17-19 soil classes – 5 scenarios = up to 900 separate simulations ● Distribute results over county/soil class cells, sum for county-level output m 2 applicable per county

8. Institute of Atmospheric Sciences South Dakota School of Mines and Technology Results: Land use distribution km 2 in each land use: Cropland - CT Grazing/Pasture

9. Institute of Atmospheric Sciences South Dakota School of Mines and Technology Carbon stock changes since 1990 Variability in annual  C, Montana  C, Mg ha -1 yr -1

10. Institute of Atmospheric Sciences South Dakota School of Mines and Technology State-level C stock trends Default +25% NT

11. Institute of Atmospheric Sciences South Dakota School of Mines and Technology Role of Ag Soil C in State GHG Budgets

12. Institute of Atmospheric Sciences South Dakota School of Mines and Technology Cheyenne River Sioux Reservation Pilot Trade ≥ 62,000 MTCE/5yrs

13. Institute of Atmospheric Sciences South Dakota School of Mines and Technology Support provided by: DOE Regional Carbon Sequestration Partnerships