Plant Growth Regulators and N Fertilization on the Partitioning of Red Clover Growth.

Plant growth regulators (PGRs) are plant hormones that are commonly used in the agricultural industry to modify plant growth responses. Because the majority of research in the forage industry has focused on the responses of grasses to PGRs, less is known about the impact these compounds may have on the growth of forage legume species.  The focus of this study was to evaluate the effects of multiple types of PGRs, and their interaction with N fertilizer, on the production and partitioning of growth in red clover [Trifolium pratense].  Ten PGR treatments and three N rates [0, 75, & 150 lbs N acre^-1] were factorially arranged as a RCBD with four replications.  PGR treatments included a control, three pre-emergent treatments [water, 5 & 10 µM 2-chloroethylphosphonic acid (2CEP)] applied to seed, and six post-emergent treatments [0.35 &0.70 oz acre^-1 gibberellin A3 (GA₃), 0.35 &0.70 oz acre^-1 GA₄ & GA₇, and 0.30 & 0.60 oz acre^-1 6-benzyladenine] applied twice to seedlings with a minimum of two trifoliate leaves.  Soaking the seed in water increased (P < 0.05) the number of red clover seedlings emerged 5 days after seeding (DAS).  However, there was no difference between this treatment and the control 9 DAS.  Despite clear visual effects from the post-emergent treatments, there were no differences in yield or leaf ground cover relative to the control. Red clover seed treated with 2CEP had a fewer (P < 0.05) number seedlings, lower yields, and provided less ground cover than the other PGR treatments throughout the study.  From the results of the study, it seems there may be little advantage from the use PGRs in forage systems containing red clover.  However, there may be additional benefits from use of PGRs in mixed grass-legume stands that were not evaluated in the current study.