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

Authors: KUMAR, VIPIN - Virginia Tech; SINGH, VIJAY - Virginia Tech; FLESSNER, MICHAEL - Virginia Tech; REITER, MICHAEL - Virginia Tech; Mirsky, Steven; HAYMAKER, JOSEPH - Virginia Tech

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2023
Publication Date: 4/20/2023
Citation: Kumar, V., Singh, V., Flessner, M., Reiter, M., Mirsky, S.B., Haymaker, J. 2023. Cover crop termination options and application of remote sensing for evaluating termination efficiency. PLOS ONE. 18(4). Article e0284529. https://doi.org/10.1371/journal.pone.0284529.
DOI: https://doi.org/10.1371/journal.pone.0284529

Interpretive Summary: Cover crops that survive the winter must be successfully killed before a cash crop can be planted; this is critical to the successful use of cover crops. It can be labor-intensive and time-consuming to estimate which herbicides are most efficient terminating cover crops in order to best advise farmers as to management options. New technology, such as unmanned aerial vehicles equipped with sensors, could address this problem. This study investigated the use of cameras mounted on drones and several indices derived from the resultant data to determine which termination methods worked best on wheat, cereal rye, hairy vetch, and rapeseed. The Green Leaf Index worked best for determining termination efficiency for cereal rye and wheat while the Normalized Difference Vegetation Index worked best for rapeseed. A blanket application of the herbicide glyphosate was not sufficient for terminating any of the cover crops; rather, the glyphosate should be mixed with another herbicide such as 2,4-D. This work benefits researchers by providing a more efficient experimental protocol, and farmers by providing concrete recommendations to successfully terminate cover crops.

Technical Abstract: Efficient termination of cover crops is an important component of cover crop management. Information on termination efficiency can help in devising management plans but estimating herbicide efficacy is a tedious task and potential remote sensing technologies and vegetative indices (VIs) have not been explored for this purpose. This study was designed to evaluate potential herbicide options for the termination of wheat (Triticum aestivum L.), cereal rye (Secale cereale L.), hairy vetch (Vicia villosa Roth.), and rapeseed (Brassica napus L.), and to correlate different VIs with visible termination efficiency. Nine herbicides and one roller-crimping treatment were applied to each cover crop. Among different herbicides used, glyphosate, glyphosate + glufosinate, paraquat, and paraquat + metribuzin provided more than 95% termination for both wheat and cereal rye 28 days after treatment (DAT). For hairy vetch, 2,4-D + glufosinate, and glyphosate + glufosinate, resulted in 99 and 98% termination efficiency, respectively, followed by 2,4-D + glyphosate, and paraquat with 92% termination efficiency 28 DAT. No herbicide provided more than 90% termination for rapeseed and highest control was provided by paraquat (86%) and 2,4-D + glufosinate (85%), and 2,4-D + glyphosate (85%). Roller-crimping (without herbicide application) did not provide effective termination of any crop with 41, 61, 49, and 43% termination for wheat, cereal rye, hairy vetch, and rapeseed, respectively. Among the VIs, Green Leaf Index had the highest Pearson correlation coefficient for wheat (r = -0.786, p = <0.0001) and cereal rye (r = -0.804, p = <0.0001) with visible termination efficiency rating. Whereas for rapeseed, the Normalized Difference Vegetation Index (NDVI) had the highest correlation coefficient (r = -0.655, p = <0.0001). The study highlighted the need for tankmixing 2,4-D or glufosinate with glyphosate for termination instead of blanket application of glyphosate for all crops including rapeseed and other broadleaf cover crops.