Published online by Cambridge University Press: 20 January 2017
Switchgrass is a potential feedstock for cellulosic bioenergy production.Weed competition from annual grass during the establishment year can reduceswitchgrass establishment and resulting productivity, but the relationshipbetween early season grass densities and outcomes of competition are notwell understood. We measured how a range of giant and yellow foxtaildensities in the establishment year influenced switchgrass establishment andresulting productivity in the first production year (second year of thegrowing season). In two of the three site–yr more than four foxtail plants m−2 reduced switchgrass plant densities below documentedthresholds of establishment success. A lesser effect of foxtails in thethird site–year suggested that higher switchgrass emergence rates reducedfoxtail competitive ability during establishment. Effects on yield wereconsistent over the three site–yr. The yield (10.96 Mg ha−1 ±0.77) decreased rapidly as foxtail density increased. One foxtail plant m−2 reduced switchgrass yield in the first production year by25%, and yield loss was 90% or greater at densities > 50 foxtail plants m−2. Although switchgrass can establish in the presence offoxtail competition, these weed species should be controlled to maximizeyields in the first production year.
Associate editor for this paper: Anita Dille, Kansas State University.