PLANT-GROWTH REGULATOR EFFECTS ON GROWTH AND FORAGE QUALITY OF TALL FESCUE

Forage quality of tall fescue (Festuca arundinacea Schreb.) is low in the spring after heading. Plant growth regulators (PGRs) have been sho wn to improve forage quality through inhibition of seedhead developmen t. The objective of this study was to compare the effect of fall or sp ring application of six PGRs on heading, yield, and forage quality of tall fescue. The soil was an Etowah silt loam (fine-loamy, siliceous, thermic Typic Paleudults). Precipitation was more favorable in the sec ond year of the experiment than in the first. Sethoxydim (2[ 2-(ethylt hio)propyl]-3-hydroxy-2-cyclohexen-1-one) at 70 g ha-1, haloxyfop meth yl (methyl trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid) at 45 g ha-1, and mefluidide 2,4-dimethyl-5-[[(trifluoromethyl)-sulfonyl ]amino] phenyl]acetamide) at 280 g ha-1 were the most consistent in re ducing head density, forage yield, and neutral detergent fiber (NDF) a nd increasing crude protein (CP) of the May harvest. The PGRs were mor e effective in reducing yield, head density, and NDF and increasing CP of the May harvest when applied in April than when applied in Decembe r of the second year. Responses to the PGRs in the May harvest were fe wer in the first year when precipitation was less favorable. Only one PGR increased in vitro dry matter digestibility (IVDMD) in the second year and none increased it in the first year. Four April-applied PGRs decreased NDF in the first year's regrowth and April-applied sethoxydi m and December-applied mefluidide increased CP in both years' regrowth . Forage quality was not consistently improved by the use of PGRs on t all fescue. An effective PGR may be more useful in turf areas than on forage because it reduces yield substantially.