Comparison of three plant growth regulators and urea on a Canterbury dairy pasture

Abstract

Two plant growth regulator (PGR) products currently available in New Zealand and a new Ravensdown PGR product-ExpressTM*, all based on gibberellic acid (GA3), were applied to a Canterbury dairy pasture in late winter (August) and early spring (September) and their effect on dry-matter (DM) yield was measured. PGR treatments were compared with both an application of liquid urea (20 kg N/ha) alone and a urea plus Express treatment. In the first harvest of both winter- and spring-initiated trials, a month following PGR application, the PGR treatments produced significant increases in DM yield ranging from 18-51% over the control. These increases, however, did not extend to the second harvest in either trial for any of the PGR agents. The application of urea increased production in the 1st harvest by ~36% in both trials but this was increased to over 60% when combined with ExpressTM. No effect of the PGR was apparent in the second harvest where the urea treatment alone was the highest DM producer. These trials showed some benefit in the use of PGR products when there is a need to boost pasture growth in early spring but these benefits largely disappeared after the first month following application.Some future research may be useful to further optimise parameters for the use of PGR products.