Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2004
Publication Date: 7/31/2004
Citation: Frank, A.B., Berdahl, J.D., Hanson, J.D., Liebig, M.A., Johnson, H.A. 2004. Biomass and carbon partitioning in switchgrass. Crop Science. 44(4):1391-1396. Interpretive Summary: Increases in atmospheric carbon dioxide levels has placed added emphasis on understanding the role of agriculture in mitigating this increase. The vast acreage of perennial grasslands that contain high levels of soil organic carbon suggests that grassland agriculture can sequester atmospheric carbon dioxide. Switchgrass is a perennial grass species that is being proposed as a biofuels crop. Switchgrass also has many traits that make it an attractive crop for sequestration of atmospheric carbon dioxide. This study determined biomass and carbon partitioning among aboveground and belowground plant components in switchgrass and changes in soil organic carbon from growing switchgrass. Aboveground plant biomass accounted for 18 percent, roots 27 percent, and crown tissue 55 percent of total plant biomass and biomass carbon. Soil carbon to 0.9-m depth increased at the rate of 1 kg carbon per m2 per yr. The quantity of carbon lost through soil respiration processes was equal to 44 percent of the carbon content of the total plant biomass. These results suggest that switchgrass plantings have potential for storing a significant quantity of soil carbon in Northern Great Plains plantings.
Technical Abstract: Grasslands possess a significant underground biomass component that serves as a large carbon storage sink for atmospheric carbon dioxide. Grassland agriculture also has potential to act as a source of renewable energy through the production of a biofuel crop. Switchgrass (Panicum virgatum L) has been promoted as a biofuel crop. Our objectives were to determine biomass and carbon partitioning in aboveground and belowground plant components and changes in soil organic carbon in field grown switchgrass. The cultivars Sunburst and Dacotah were field grown over three years at Mandan, ND. Aboveground biomass was sampled on eight dates each year and separated into leaves, stems, senescence biomass, and litter. Root biomass to 1.1 m depth and soil organic carbon to 0.9 m depth was determined in depth increments each year. Soil carbon loss from respiratory processes was determined by measuring carbon dioxide flux about every 21 days from early May to late Oct. At seed ripe harvest, stem biomass accounted for 46 percent of total aboveground biomass, leaves 7 percent, senescence plant parts 43 percent, and litter 4 percent. Excluding crowns, root biomass averaged 27 percent of the total plant biomass and 84 percent when crown tissue was included with underground biomass. Carbon partitioning among aboveground, crown, and root biomass showed that crown tissue contained more than 50 percent of the total biomass carbon. Regression analysis indicated that soil organic carbon to 0.9 m depth increased at the rate of 1.01 kg carbon per m2 per yr. The quantity of carbon lost through soil respiration processes was equal to 44 percent of the carbon content of the total plant biomass. Although nearly half of the carbon captured in plant biomass during a year is lost through soil respiratory processes the quantity of soil carbon gain indicates that Northern Great Plains switchgrass plantings have potential for storing a significant quantity of soil carbon.