Assessing winter cereals as cover crops for weed control in reduced-tillage switchgrass establishment

Weed pressure is a major challenge in switchgrass (Panicum virgatum L.) establishment. The objective of this study was to assess whether cereal cover crops alone can control weeds and improve switchgrass stand establishment in reduced-tillage system or whether herbicide treatments should be applied. Field experiments were conducted at the University of Massachusetts Agricultural Experiment Station in Deerfield in 2010-2011 and 2012-2013 growing seasons. A split plot design with three replications was used. The main plots consisted of three cover crop treatments [fallow, oat (Avena sativa L.) and rye (Secale cereale L.)]. The sub-plots were herbicide treatments that consisted of no herbicide or post-emergence application of atrazine (A) (1.1 kg a.i. ha−1) and quinclorac (Q) (0.37 kg a.i. ha−1). Herbicides were applied when switchgrass was at 4-leaf stage (6 weeks after planting). Switchgrass tiller density was 100% improved with application of A + Q. Rye provided more effective weed control than oat; however, tiller density of switchgrass was also lower in rye treatment compared with oat and fallow. Switchgrass biomass yield was significantly lower in nontreated herbicide plots (0.22 Mg ha−1) than plots receiving A + Q (0.41 Mg ha−1). Our findings suggested that supplemental herbicide application is needed with using cover crops to improve switchgrass establishment.