Herbicide selection to terminate grass, legume, and brassica cover crop species

Abstract

Cover crops provide a number of agronomic benefits, including weed suppression, which is important as cases of herbicide resistance continue to rise. To effectively suppress weeds, high cover crop biomass is needed, which necessitates later termination timing. Cover crop termination is important to mitigate potential planting issues and prevent surviving cover crop competition with cash crops. Field studies were conducted in Virginia to determine the most effective herbicide options alone or combined with glyphosate or paraquat to terminate a range of cover crop species. Results revealed that grass cover crop species were controlled (94% to 98%) by glyphosate alone 4 wk after application (WAA). Overall, legume species varied in response to the single active-ingredient treatments, and control increased with the addition of glyphosate or paraquat. Mixes with glyphosate provided better control of crimson clover and hairy vetch by 7% to 8% compared with mixes containing paraquat 4 WAA. Mix partner did not influence control of Austrian winter pea. No treatment adequately controlled rapeseed in this study, with a maximum of 58% control observed with single active-ingredient treatments and 62% control with mixes. Height reduction for all cover crop species supports visible rating data. Rapeseed should be terminated when smaller, which could negate weed suppressive benefits from this cover crop species. Growers should consider herbicide selection and termination timing in their cover crop plan to ensure effective termination.

Cover crop termination options and application of remote sensing for evaluating termination efficiency

“…At 28 DAT, thifensulfuron + tribenuron and glyphosate provided 79 and 74% termination efficiency ( Table 6 ). Similar results were observed by Pittman et al, [ 22 ], where 80, 87, 81, and 69% termination efficiency at 28 DAT with 2,4-D, dicamba, glufosinate, and glyphosate was reported. All termination treatments reduced hairy vetch biomass 28 DAT.…”

“…Thifensulfuron + tribenuron provided 43 and 51% termination 14 and 28 DAT. Askew et al, [ 21 ] and Pittman et al, [ 22 ] reported 34–70%, 9–40%, 50–67%, and 50–68% termination efficiency with 2,4-D, dicamba, glufosinate, and paraquat, respectively. Greater termination efficiency with paraquat in this study is attributed to greater spray volume used.…”

“…Similarly, in a study conducted in Arkansas, Palhano et al, [ 20 ] reported greater than 95% termination efficiency for cereal rye and wheat with the application of glyphosate. However, glyphosate is not effective for the termination of non-grass species [ 21 , 22 ]. For instance, previous studies have found that termination efficiencies ranged from 56–69% in legumes and 58–86% for brassicas when using glyphosate [ 20 ].…”

“…For instance, previous studies have found that termination efficiencies ranged from 56–69% in legumes and 58–86% for brassicas when using glyphosate [ 20 ]. Other popular herbicides such as 2,4-D and dicamba provide improved termination efficiencies for hairy vetch (80–87%) but very poor efficiencies for rapeseed (10–34%) [ 22 ]. However, glufosinate, another non-selective herbicide, showed the highest termination efficiency for hairy vetch (95%) [ 20 ], while showing a decreased efficiency (79%) compared to glyphosate (94–99%) for cereal rye [ 9 ].…”

Estimating the Reduction in Cover Crop Vitality Followed by Pelargonic Acid Application Using Drone Imagery

“…Cover crops are either damaged or killed by frost in winter (frost-sensitive cover crops) or actively desiccated by mowing, tillage, or application of chemical herbicides. The application of a non-selective herbicide (e.g., the active ingredient glyphosate) is a common method for desiccating cover crops because, compared with other desiccation methods, it can offer suitable levels of control at almost any time or plant growth stage [4][5][6]. However, a delay in desiccating the cover crop carries risks associated with the next crop emergence, such as water moisture depletion [3,7,8] and nitrogen immobilisation [8].…”