Effect of Mefluidide on Cool‐Season Perennial Grass Forage Yield and Quality1

Abstract

AbstractSeasonal forage production of cool‐season perennial grasses is not uniform. Spring production is often under‐utilized in pastures while deficits frequently occur in the summer. We determined the effect of date of mefluidide {N‐[2,4‐dimethyl‐5‐[[(trifluoromethyl)sulfonyl] amino]phenyl]acetamide} application on distribution of forage yield and quality of orchardgrass (Dactylis glomerataL.), tall fescue (Festuca arundinaceaSchreb.), reed canarygrass (Phalaris arundinaceaL.), smooth bromegrass (Bromus inermisLeyss.), and Kentucky bluegrass (Poa pratensisL.) and the effect of a prespray clipping of these grasses on mefluidide activity. Two field experiments were each conducted for 2 yr on a fine‐silty over sandy or sandy‐skeletal, mixed, mesic Typic Hapludoll. In the first experiment, mefluidide (0.42 kg/ ha) was applied to the grasses in late September, late April, or mid‐May. In the second, mefluidide (0.42 kg/ha) was applied to the initial grass growth in early to mid‐May or to regrowth in late May to early June following an early spring defoliation. Forage dry matter yield and quality responded differently to mefluidide treatments each year in both experiments possibly due to differences in grass morphological development at application. However, all grass species responded similarily in yield or quality to meflufdide treatment. A late April mefluidide application (grasses vegetative, no culm elongation) consistently increased first harvest leafiness and forage quality compared to the control. Mean (over 2 yr) leaf/stem ratios and crude protein and neutral detergent fiber concentrations were 2.7, 16.3 dag/kg, and 54.6 dag/kg, respectively, for the April mefluidide treatment and 1.1, 13.1 dag/kg, and 61.5 dag/kg, respectively, for the control. However, increased forage quality was accompanied by decreased first harvest yields (mean yields of 2.0 and 4.0 Mg/ha for the April mefluidide treatment and control, respectively). Clipping spring growth before applying mefluidide to the regrowth had no consistent effect on grass forage yield or quality. Increased forage quality of the first crop due to mefluidide treatment may justify its use in extensive systems where surplus spring growth is usually wasted.