MEFLUIDIDE EFFECT ON WEEPING LOVEGRASS HEADING, FORAGE YIELD, AND QUALITY

Weeping lovegrass [Eragrostis curvula (Schrad.) Nees.] provides high quality forage during May, but growth of floral stems causes a rapid decline in forage quality. The study objective was to determine which combination of date and rate of mefluidide[N-(2,4-dimethyl-5-{[(trifluoro methyl)sulfonyl]amino}phenyl)acetamide], a growth regulator, would effectively decrease number of floral stems and thus maintain higher forage quality. Mefluidide (0.00, 0.28, 0.56, and 0.84 kg/ha) was applied to lovegrass on 1 of 3, 2, 5, and 5 dates in 1984, 1985, 1986, and 1987, respectively. Lovegrass was grown on a Pratt fine sandy loam (Thermic Psammentic Haplustalf) soil near Woodward, Okla. Factorial combinations of treatments were rerandomized within the study area each year. Plots (1.8 by 5 m) were replicated 6 times in a randomized complete block design. Forage was harvested in mid June to early July with a sickle bar at seed ripe. Mefluidide reduced the number of floral stems only when applied 1 week after floral primordium initiation. Mefluidide application 1 week earlier or later had little effect on number of floral stems, forage yield, in vitro dry matter digestibility (IVDMD), or crude protein (CP). Application of 0.56 kg/ha of mefluidide 1 week after floral primordium initiation decreased number of floral stems 58 to 93%, decreased forage yield 14 to 23%, increased percent leaves 4 to 32 percentage units, and had little effect on leaf yield. It increased whole-plant IVDMD 1.6 to 2.8 and CP 0.2 to 1.6 percentage units depending upon year. Generally, mefluidide had little effect on leaf or stem IVDMD or CP that averaged 49 and 7.5% for leaves and 39 and 5.1% for stems, respectively. The effective 'window' for mefluidide application is probably too short for practical use by farmers or ranchers.