Carbon Sequestration and Soil Organic Carbon Storage

Grogan and Mathews (2001) reviewed available soil C sequestration models and concluded then that the CENTURY model seemed to have the best potential for adaptation to bioenergy crop systems because of its integrated plant-soil approach and the availability of specific forestry subroutines. Not surprisingly, the model has been incorporated into many crop growth models, such as EPIC and DAYCENT to simulate SOC dynamics along with crop growth (Del Grosso et al. 2005; Izaurralde et al. 2006).

Available lands for biofuel production are very limited; therefore, meeting the feedstock needs of the bioenergy industry may require the conversion of agricultural lands to bioenergy crops. Land-use change consequently affects the ecosystem C balance. Corn, soybeans, and wheat are the three major crops with the highest production among food crops in U. S., and switchgrass and Miscanthus are two second-generation biofuel crops with the potential to produce a large amount of biofuel feedstocks and mitigate carbon emissions (Parrish and Fike 2005; Tilman et al. 2009; Pimentel et al. 2010). Davis et al. (2011) used the DAYCENT model to estimate the amount of N leaching and storage of soil C when replacing lands currently growing corn with perennial biofuel grasses. Overall, the model predicted a significant decrease in N leaching up to 24% and an increase in SOC up to 2.8% when land use changed from corn to switchgrass. These results are consistent with field studies showing that perennial grasses like switchgrass can store 1.1 Mg C ha1 yr-1 in the upper 1 m of the soil on conservation reserve program lands (Gebhart et al. 1994). In another field study, McLaughlin and Walsh (1998) reported that soils under switchgrass production had SOC sequestration rates reaching 20 to 30 times greater than soils under annual row crops. Furthermore, McLaughlin et al. (2002) revealed that switchgrass grown on bioenergy research plots could add 1.7 Mg C ha-1 yr-1.