Evaluation of miscanthus productivity and water use efficiency in southeastern United States

Authors: MALESKI, JEROME; Bosch, David - Dave; Anderson, Raymond - Ray; Coffin, Alisa; Anderson, William - Bill; Strickland, Timothy - Tim

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2019
Publication Date: 7/26/2019
Citation: Maleski, J.J., Bosch, D.D., Anderson, R.G., Coffin, A.W., Anderson, W.F., Strickland, T.C. 2019. Evaluation of miscanthus productivity and water use efficiency in southeastern United States. Science of the Total Environment. 692:1125-1134. https://doi.org/10.1016/j.scitotenv.2019.07.128.
DOI: https://doi.org/10.1016/j.scitotenv.2019.07.128

Interpretive Summary: Biofuel productivity for dryland miscanthus (Illinois strain) and irrigated corn in Georgia, USA were quantified using an eddy covariance system that measures crop water use and net carbon gain or loss. Miscanthus harvest was 15.54 Mg/ha in 2015 and 11.80 Mg/ha in 2016, while corn produced 30.20 Mg/ha of biomass in 2016. Carbon budgets indicated that both miscanthus and corn systems had a net carbon loss. The miscanthus field lost 5 Mg C/ha/year the corn field lost 1.37 Mg C/ha/year. Miscanthus used 598 mm of water resulting in water use efficiencies that ranged from 6.95-13.84 kg C/ha/mm. Corn used 659 mm of water resulting in a water use efficiency of 19.12 kg C/ha/mm. The net carbon loss from both miscanthus and corn appeared to be driven by very high carbon respiration resulting from soil organic matter decomposition and crop energy requirements. Relatively low biomass production, low water use efficiency and high respiration for miscanthus in this experiment suggest that this strain may not be well-suited for dryland production under the environmental conditions (hot and periodically dry) found in South Georgia USA.

Technical Abstract: Second generation biofuels, such as perennial grasses, have potential to provide biofuel feedstock while growing on degraded land with minimal inputs. Perennial grasses have been reported to sequester large amounts of soil organic carbon (SOC) in the Midwestern United States (USA). However, there has been little work on biofuel and carbon sequestration potential of perennial grasses in the Southeastern US. Biofuel productivity for dryland Miscanthus x gigantus and irrigated maize in Georgia, USA were quantified using eddy covariance observations of evapotranspiration (ET) and net ecosystem exchange (NEE) of carbon. Miscanthus biomass yield was 15.54 Mg ha-1 in 2015 and 11.80 Mg ha-1 in 2016, while maize produced 30.20 Mg ha-1 of biomass in 2016. Carbon budgets indicated that both miscanthus and maize fields lost carbon over the experiment. The miscanthus field lost 5 Mg C ha-1 in both 2015 and 2016 while the maize field lost 1.37 Mg C ha-1 for the single year of study. Eddy covariance measurement indicated that for 2016 the miscanthus crop evapotranspired 598 mm and harvest water use efficiencies ranged from 6.95-13.84 kg C ha-1 mm-1. Maize evapotranspired 659 mm with a harvest water use efficiency of 19.12 kg C ha-1 mm-1. While biomass yields and gross primary production were relatively high, high ecosystem respiration rates resulted in a loss of ecosystem carbon. Relatively low biomass production, low water use efficiency and high respiration for Miscanthus x gigantus in this experiment suggest that this strain of miscanthus may not be well-suited for dryland production under the environmental conditions found in South Georgia USA.