EFFECT OF MEFLUIDIDE APPLICATION DATE ON YIELD AND FORAGE QUALITY OF Bromus SPECIES

The plant growth regulator mefluidide (N- [2,4-dimethyl 5 [[(trifluoromethyl)sulfonyl] amino] phenyl] acetamide) has been used to enhance forage quality in several temperate grass species, but results have been inconsistent. This study was carried out to determine if stage of apical development at time of mefluidide application influenced subsequent forage yield and quality. Mefluidide was applied at 0.3 kg ha −1 to smooth bromegrass (Bromus inermis Leyss.) and meadow bromegrass (Bromus biebersteinii Roem and Schult.) at six weekly intervals beginning 27 April during 1984 and 1985 at Lacombe, Alberta. Stage of apical development at mefluidide application time was monitored closely in smooth bromegrass. Dry matter (DM) yield and quality parameters were measured at the hard dough stage. Maximum yield reductions and quality enhancement occurred consistently following an application during the first week in May. This application time (2–4 May) corresponded to a developmental stage just prior to jointing and after double ridge formation in smooth bromegrass. The 2–4 May application resulted in a 26 and 43% reduction in DM yield, a 7.8 and 6.2% increase in in vitro digestible organic matter (IVDOM) and a 41 and 50% increase in crude protein for smooth and meadow bromegrass, respectively. Fiber fractions, except hemicellulose, both on a DM and cell-wall basis, were also lowest at this application date for both species. IVDOM was negatively correlated to plant height and lignin content both on a cell-wall and DM basis. This indicated that improved quality was associated with a reduction in stem material. A negative correlation between plant height and yield was also observed. It is recommended that, for quality enhancement in smooth and meadow bromegrass, mefluidide be applied after growth has resumed in spring, but prior to jointing.Key words: Bromus species, mefluidide, application date, forage yield and quality