Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2009
Publication Date: 1/12/2010
Publication URL: http://hdl.handle.net/10113/40267
Citation: Garten, C.T., Smith, J.L., Tyler, D.D., Amonette, J.E., Bailey, V.L., Brice, D.J., Castro, H.F., Graham, R.L., Gunderson, C.A., Izaurralde, R.C., Jardine, P.M., Jastrow, J.D., Kerley, M.K., Matamala, R., Mayes, M.A., Metting, F.B., Miller, R.M., Moran, K.K., Post, W.M., Sands, R.D., Schadt, C.W., Phillips, J.R., Thomson, A.M., Vugteveen, T., West, T.O., Wullschleger, S.D. 2010. Intra-Annual Changes in Biomass, Carbon, and Nitrogen Dynamics at 4-Year Old Switchgrass Field Trials in West Tennessee, USA. Agriculture, Ecosystems and Environment. 136:177-184 Interpretive Summary: Switchgrass is a potential bioenergy crop that could promote fuel security and soil C sequestration in some environments. As switchgrass grows a significant amount of CO2 fixed from the atmosphere is placed in roots belowground. If grasses such as switchgrass can be grown on marginal land the benefits to the U.S. would be a source of solar fixed energy and reduction of the nation’s overall carbon footprint. We found no difference between cultivars of switchgrass for biomass carbon and nitrogen. The belowground plant biomass was about 25% of the aboveground plant biomass, suggesting a significant input to the soil and potential for long-term storage. This study will be important to scientists, industry and growers who are trying to develop green energy production systems. It will also be important for entities such as the Chicago Climate exchange in moving forward a carbon credit system for agricultural crops.
Technical Abstract: Switchgrass is a potential bioenergy crop that could promote soil C sequestration in some environments. We compared four switchgrass cultivars on a well-drained Alfisol to test for differences in biomass, C, and N dynamics during the fourth growing season. There was no difference (P >0.05) among cultivars and no significant cultivar x time interaction in analyses of dry mass, C stocks, or N stocks in aboveground biomass and surface litter. At the end of the growing season, mean (±SE) aboveground biomass was 2.1 ±0.13 kg m-2, and surface litter dry mass was approximately 50% of aboveground biomass. Prior to harvest, the live root:shoot biomass ratio was 0.77. There was no difference (P >0.05) among cultivars for total biomass, C, and N stocks belowground. Total belowground biomass (90 cm soil depth) as well as coarse (=1 mm diameter) and fine (<1 mm diameter) live root biomass increased from April to October. Dead roots were <10% of live root biomass to a depth of 90 cm. Net production of total belowground biomass (505 ±132 g m-2) occurred in the last half of the growing season. The increase in total live belowground biomass (426 ±139 g m-2) was more or less evenly divided among rhizomes, coarse, and fine roots. The N budget for annual switchgrass production was closely balanced with 6.3 g N m-2 removed by harvest of aboveground biomass and 6.7 g N m-2 supplied by fertilization. At the location of our study in west Tennessee, intra-annual changes in biomass, C, and N stocks belowground were potentially important to crop management for soil C sequestration.