Herbage Mass and Nutritive Value of Bermudagrass Influenced by Non‐Growing‐Season Herbicide Application

Abstract

Core Ideas Dormant‐season herbicide applications are effective in controlling cool‐season weeds in bermudagrass. Some dormant‐season herbicide products can negatively impact bermudagrass forage production. Dormant‐season application of glyphosate did not cause significant damage to the bermudagrass stand. Elimination of cool‐season weeds in bermudagrass may not always be advantageous. Application of herbicides to dormant bermudagrass [Cynodon dactylon (L.) Pers] in late winter to control cool‐season weeds is a possible management practice for more marketable hay harvests. The objective of this study is to determine dormant‐season herbicide effects on bermudagrass herbage mass and nutritive value at four harvest dates typical for Louisiana. The experimental design was a randomized complete block of Roundup (glyphosate), Plateau (imazapic), Journey (imazapic + glyphosate), Pastora (nicosulfuron + metsulfuron methyl), and a control (no herbicide treatment). The treatments were applied mid‐February of 2013 and 2014. Cool‐season weeds contain lower neutral detergent fiber (NDF) concentration than bermudagrass while containing higher acid detergent fiber (ADF), crude protein (CP), and in vitro dry matter digestibility (IVDMD). Pastora resulted in the highest bermudagrass composition of 65.2% (DM basis) at the first harvest, followed by Journey, Plateau, Roundup, and control treatment with 44.2, 33.6, 28.3, and 20.7%, respectively. Herbicide × harvest interaction was significant for herbage accumulation and nutritive value. Pastures receiving Pastora and Journey accumulated less herbage with lower CP concentration than pastures receiving Roundup and control due to lower weed composition. Year × herbicide interaction was significant and herbage mass from Pastora treated pasture was lower in 2014 than 2013. It was concluded that dormant‐season herbicide applications may be beneficial for producing a weed‐free first harvest of bermudagrass hay, but may sacrifice some nutritive value provided by the inclusion of cool‐season herbage mass, grass, and broadleaf weeds, in the harvested product.