Improving Nutritive Value of Native Warm‐Season Grasses with the Plant Growth Regulator Trinexapac‐Ethyl

Abstract

Livestock producers in the southeastern United States utilize native warm-season grasses (NWSG), however, the best management practice to not harvest during late-summer and fall results in large quantities of low quality forage. Gibberellin inhibitors can alter plant regrowth and forage value. This study assessed the impact of trinexapac-ethyl [TE; ethyl 4-(cyclopropyl-hydroxymethylene)-3,5-dioxo-cyclohexane-1-carboxylate] on fall NWSG forage. Application of TE occurred in late July at four levels (0, 0.3, 0.6, and 1.2 kg a.i. ha-1) to switchgrass (SG; Panicum virgatum L.) and a mixed sward (BBIG) of big bluestem (Andropogon gerardii Vitman) and indiangrass (Sorghastrum nutans L.) during 2016 and 2017. Forage mass (FM) and nutritive value [crude protein (CP), neutral detergent fiber (NDF), in vitro true dry matter digestibility (IVTDMD)] were evaluated monthly. Application reduced fall FM (SG: 37%; BBIG: 42%). Switchgrass nutritive value did respond to TE application. Application of TE reduced BBIG NDF overall, but strong annual variation occurred due to a drought (2016). Analyzed separately, 2017 treated BBIG samples (1.2 kg a.i. ha-1) exhibited altered FM (−57%), CP (up to 54%), NDF (−9.2%), and IVTDMD (11%). Further analysis provided tentative evidence that TE improved leaf nutritive value and increased leaf proportion, although overall leaf yield was not improved. Overall, TE improved BBIG nutritive value but at a substantial FM loss. Since poor nutritive content forage has negligible value regardless of quantity, growth regulators could improve outcomes of fall NWSG management by adding value to an unutilized resource.

Above- and Below-Ground Part Growth in Chewings and Strong Creeping Red Fescue Grown for Seed Resulting from Retardants and N Fertilization

“…This could have been due to thickening of the tillers or increased leaf weight. Tilhou and Nave [21] showed an increase in leaf proportion on fall native worm season grasses forage after the application of TE. Rademacher [14] claims that TE is inhibiting the activity of enzyme 3-β hydroxylase that the transforms inactive gibberellins form GA20 on highly active forms GA1 and GA3, which causes growth reduction and stem wall thickening.…”

Leaf Physiological and Water Soluble Carbohydrate Content Responses to Trinexapac-ethyl Application of Sports Turf Grasses Exposed to Water Stress

“…This involves the synthesis and accumulation of compatible solutes including water soluble carbohydrates [15][16][17], which have been used as a physiological measure to evaluate stress tolerance in different plants [12,18,19]. A common cultural practice in turf grass management is the use of plant growth regulators (PGRs) [20]. Trinexapac-ethyl (TE) is one of the most widely use PGR in cool-season and warm-season turf grass management [8,21,22], applied mainly to reduce mowing frequency and improve overall turf quality [23].…”