Biomass and Carbon Partitioning in Switchgrass

Abstract

Grasslands have an underground biomass component that serves as a carbon (C) storage sink. Switchgrass (Panicum virgatum L.) has potential as a biofuel crop. Our objectives were to determine biomass and C partitioning in aboveground and belowground plant components and changes in soil organic C in switchgrass. Cultivars Sunburst and Dacotah were field grown over 3 yr at Mandan, ND. Aboveground biomass was sampled and separated into leaves, stems, senesced, and litter biomass. Root biomass to 1.1‐m depth and soil organic C to 0.9‐m depth was determined. Soil C loss from respiratory processes was determined by measuring CO2 flux from early May to late October. At seed ripe harvest, stem biomass accounted for 46% of total aboveground biomass, leaves 7%, senesced plant parts 43%, and litter 4%. Excluding crowns, root biomass averaged 27% of the total plant biomass and 84% when crown tissue was included with root biomass. Carbon partitioning among aboveground, crown, and root biomass showed that crown tissue contained approximately 50% of the total biomass C. Regression analysis indicated that soil organic C to 0.9‐m depth increased at the rate of 1.01 kg C m−2 yr−1 Carbon lost through soil respiration processes was equal to 44% of the C content of the total plant biomass. Although an amount equal to nearly half of the C captured in plant biomass during a year is lost through soil respiration, these results suggest that northern Great Plains switchgrass plantings have potential for storing a significant quantity of soil C.

Managing and enhancing switchgrass as a bioenergy feedstock

“…43 Frank et al 33 reported that soil C increased at a rate of emissions from switchgrass-based ethanol were 94% lower than estimated GHG emissions from gasoline. 41 In addition to increasing soil carbon (C), growing switchgrass may increase wildlife habitat, increase landscape and biological diversity, increase farm revenues, and return marginal farmland to production.…”

“…In North Dakota, Frank et al 33 applied 67 kg N ha −1 in the autumn and harvested at the soil level for a 3-year average biomass yield of 6.4 and 9.1 Mg ha −1 for the upland cultivars Dacotah and Sunburst, respectively.…”

Switchgrass for bioethanol and other value-added applications: A review

“…Wu et al (2006) estimated that the net amount of CO 2 sequestered would be around 48.5 kg per dry metric ton of switchgrass. Frank et al (2004) examined Sunburst and Dacotah switchgrass cultivars and noted that the net system carbon gain doubled over a three-year period. Combined with the zero net carbon exchange as a result of burning bioethanol from switchgrass, addition of soil carbon results in the overall reduction of atmospheric release of CO 2 (Lynd et al, 1991).…”

Soil Carbon Sequestration by Switchgrass and No-Till Maize Grown for Bioenergy

“…Perennial grasses such as switchgrass (Panicum virgatum L.) are known to sequester SOC [13][14][15][16][17], but the long-term effects of management practices such as N fertilization rate and harvest management on SOC sequestration by switchgrass are unknown. Perennial grasses could be used as bioenergy crops on about 20 million ha (ha010,000 m 2 ) of marginal or idle cropland in the USA alone [18].…”