Can winter cover crop termination practices impact weed suppression, soil moisture, and yield in no-till soybean [Glycine max (L.) Merr.]?

Timing and methods used to kill or terminate fall-planted cover crops vary among farmers, and can affect levels of benefits received in the succeeding cash crop. Field experiments were conducted at two sites in Maryland during the 2013 and 2014 growing seasons to examine how varying the termination date and method of barley (Hordeum vulgare L.) affects the weed community, soil moisture, and yield in succeeding no-till soybean (Glycine max L.) plantings. Experimental treatments included early-kill with pre- and post-emergent herbicides (EK), late-kill with pre- and post-emergent herbicides (LK), late-kill with a flail mower and pre-emergent herbicides (FM), and a fallow/bare-ground check with pre- and post-emergent herbicides (BG). Terminating the barley late or just prior to soybean planting resulted in significantly greater barley biomass accumulation in LK and FM than EK. The EK treatment had the highest weed pressure among treatments. However, increased biomass in LK and FM did not result in greater weed suppression than the BG treatment, and there were no differences in weed pressure between LK and FM. Method and timing of termination had no significant effect on soil moisture or yield. Results from this experiment suggest that mechanically terminating a cover crop can be as effective as using a post-emergent herbicide for managing weeds in a subsequent soybean crop if a pre-emergent herbicide is used, and that delaying cover crop termination or herbicide application until just prior to cash crop planting can result in reduced weed pressure.