Switchgrass (Panicum virgatum L.) is considered a valuable perennial biofeedstock with significant potential to sequester soil organic carbon (SOC).� A study was conducted to document SOC change under switchgrass at 10 sites along a transect from Nebraska to North Dakota (Figure 1).� The sites, located on farmer-managed fields, were sampled prior to planting switchgrass in 2000 and 2001, and again in 2005 and 2006 to determine change in SOC over time.� Sites in Nebraska were sampled to a depth of 1.2 m, while sites in North and South Dakota were sampled to 0.3 m.� Soil organic carbon increased over time (P≤0.1) in at least one sampled depth at seven sites (Streeter, ND; Highmore and Ethan, SD; Atkinson, Crofton, Douglas, and Lawrence, NE).� Soil organic carbon increased most consistently across sites at 0 to 0.05 m and below 0.2 m.� Cumulative depth assessments indicated significant increases in SOC at Streeter, ND (P=0.08), Highmore, SD (P=0.09), and Atkinson and Lawrence, NE (P=0.10 and 0.09, respectively) for the 0 to 0.3 m depth, and at Lawrence, NE (P=0.01) for the 0 to 1.2 m depth.� Rates of SOC accrual for the 0 to 0.3 m depth at responsive sites ranged from 0.9 to 1.4 Mg C ha^-1 yr^-1, while the SOC accrual rate at the Lawrence, NE site for the 0 to 1.2 m depth averaged 3.8 Mg C ha^-1 yr^-1.� On-farm documentation of increased SOC over time underscores the capacity of switchgrass to effectively sequester atmospheric C in soil.

Figure 1.� Sampling sites for on-farm evaluation of SOC change under switchgrass.