Growth regulators' effect on crested wheatgrass forage yield and quality.

If crested wheatgrass [Agropyron desertorum (Fisch.) Schult.] could be maintained in an immature growth stage, it would improve forage quality and thus extend the grazing season. In 1981 and 1982, plant growth regulators were applied to crested wheatgrass 0, 2, 4, and 6 weeks after first floral primordium initiation to determine which compound, date, and rate of application would maximize forage quality yet minimize reduction of forage yield when harvested at seed ripe stage. Mefluidide [N-(2,4-dimethyl-5{[(trifluoromethyl)-sulfonyllamino}phenyl)acetamidel at 4 rates [0.0, 0.28, 0.56, and 0.84 kg/ha active ingredient (a.i.)], maleic hydrazide (MH) (1,2-dihydro-3,6-pyridazinedione) at 4.5 kg/ha ai., and MH (3.36 kg/ha ai.) phl chlorflurenol (methyl-2-chloro-9-hydroxyfluorene-9-carboxylate) at 1.12 kg/ha a.i. were applied to crested wheatgrass growing on a Shambo loam (Typic Haploborolls) in northeast Montana. Application of MH or MH plus chlorflurenol generally gave a similar response in heading, forage yield, CP, and in vitro organic matter digestibility on a dry matter basis (IVDOMD) as did melfluidide at 0.56 kg/ha. Mefluidide (0.56 kg/ha) applied 2 weeks after first floral primordium initiation decreased heading 80 and 95%, decreased forage yield 20 and 30%, increased CP 1.7 and 2.3 percentage units, and increased IVDOMD 1.8 to 4.2 percentage units compared to untreated, depending upon