Barley residue and herbicide management practices: Effects on insects and weeds in soybean

Cover cropping has long been used as a method of reducing soil erosion, increasing soil quality and suppressing weeds. From a sustainability perspective, cover crops provide us with tools to manipulate agricultural systems. They can be used to modify weed and arthropod populations, soil moisture and fertility, and ultimately crop yield. However, effects of cover crops in local farming systems are varied and can be affected by timing and method of cover crop termination. Previous work suggests that impacts of timing and method of termination can vary from enhancing crop productivity to having no effect. Therefore, research is needed in this area so that benefits of cover crops on agricultural productivity and sustainability can be enhanced. The purpose of this study was to examine the effect of barley cover crop termination methods on weed and insect communities within soybean fields. We conducted two field studies each in Upper Marlboro and Beltsville, Maryland between 2013 and 2014. The study consisted of three cover crop and one no-cover crop (check) treatments. Cover crop treatments were Early-Kill (EK) and Late-Kill in which the cover crop was killed with a post-emergent herbicide in late April and May, respectively; and flail mow (FM), in which a flail mower was used to terminate the cover crop in late May. All treatments received a pre-emergent herbicide at time of cover crop termination and soybean was no-tilled planted in late May. In 2013, weed counts and biomass were significantly lower in LK relative to the EK treatment; and plant sucking insects (alfalfa three cornered leafhopper, potato leafhopper, aphid, etc) were consistently more numerous in EK than LK treatment. Spider numbers were greater in LK than other treatments for the 2013 season. The parasitic wasp, Telenomus podisi was found in higher numbers in FM and EK than in LK treatment plots in the 2013 growing season. Numbers of other insects encountered and soybean yield were similar among treatments. This investigation found that timing and method of cover crop termination can influence weed and some arthropods commonly found in soybean fields.