Is plant growth regulator application reliable option for forage seed crop management in the Peace River region of Canada?

Lodging related impairment of fertilization and seed development is one of the major constraints to seed yield in forage and turf-grass seed crops. Plant growth regulators (PGRs) that reduce cell elongation through the control of gibberellic hormonal activities are increasingly used for temperate forage seed crops around the world. Various study results show that the anti-gibberellic PGRs reduce plant height, diminish lodging and increase seed yield. A number of field experiments with PGRs were conducted on creeping red fescue (Festuca rubra L. ssp. rubra Gaudin), meadow bromegrass (Bromus riparius Rehm) and timothy (Phleum pratense L.) seed crops at Beaverlodge Research Farm and its outreach areas in the Peace River region. Two PGRs, trinexapac-ethyl and chlormequat chloride, were applied at two-node (BBCH 31-32) and/or early heading (BBCH 51-52) growth stages. The seed crop species exhibited differential responses to PGR application, in that creeping red fescue was least responsive, while meadow bromegrass and timothy showed moderate to high response in terms of reduction in plant height and lodging, and increasing seed yield. Those responses were highly dependent on the growing season weather condition. Generally, PGR application was more effective on seed crops with vigorous growth that received well distributed rainfall providing adequate moisture in the soil. Further studies are needed to understand physiological mechanisms for differential responses of forage seed crops to PGR application.