Plant growth regulators and pea productivity

Paul Johnstone, Sarah Pethybridge, Bruce Searle and Christina Waldon, Plant & Food Research

Commercial pea crops can flower for an extended period. When plants keep on flowering, they can put resources into pods and peas that are often underdeveloped by harvest. Conversely, if flowering can be stopped at the right times, more energy goes into the pods that make up harvestable yield.

This 2013-14 summer we conducted two preliminary comparisons at the MicroFarm to see whether plant growth regulators (PGRs) could affect flowering period and increase harvestable yield. PGRs are plant hormones that influence growth and development. There are many different types and each influences plants in different ways.

We applied a selection of commercially available PGRs to plots within early (sown in September) and late (sown in November) pea crops. The products applied included a mix of PGR types (gibberellins, anti-gibberellins, cytokinins and anti-ethylene), rates and timings. We used two application rates: the recommended dosage and double that rate of each product. The application timings were early vegetative growth, pre-flowering and flowering. The demonstration plots were not replicated.

At harvest we measured pea yields and quality in PGR-treated plots and compared these with values from plots that received no PGR application (our control). The results are presented in Table 1.

Total pea yields averaged 9.7 t/ha in the early planted crops and 6.2 t/ha in the late planted crops. We did see some effects of the PGR products on crop yields but these yields were also influenced by highly variable plant populations and crop maturity.


In the early trial, the standard rate of Regalis® applied during early vegetative growth resulted in between 2.1 and2.6 t/ha higher total yields than those in other treatments. The differences were primarily related to more peas per pod and heavier peas.

In the late trial, the double rate of Regalis applied during early vegetative growth achieved the highest total yields (8.1 t/ha), but statistically these were not significantly different from those in the untreated plants (7.6 t/ha).


20131029_webProGibb® caused rapid stem elongation and yellowing for a period, but not a yield benefit

We saw no effect of the ProGibb® treatment on yield in the early planting.

In the late planted crop, ProGibb appeared to reduce pea yields greatly, producing only between 3.4 and 3.6 t/ha. Fewer and lighter individual peas were produced on plants treated with this product.


Two cytokinin products were tried: Exilis® on the early planting and Sitofex® on the late planting. We saw no effect of either product on pea yields.


We applied Retain® to plots in the early planting but saw no effect. It was not used on the late planting.


These initial observations suggest that some PGRs may provide a potential yield benefit, although our results were confounded by variation in plant population, which has a strong effect on yield. Unravelling this interaction is necessary before firm recommendations can be made.


The trial was sown by Patrick Nicolle (Nicolle Contracting) using seed supplied by McCain Foods. PGR products were supplied by BASF Crop Protection and Agronica. Tim Robinson (Peracto Ltd) applied the various PGR treatments in both demonstrations. Additional assistance was provided by Issy Sorensen, Nathan Arnold, Matthew Norris, Tony White and Colleen Reid (Plant & Food Research) during the harvests.

PGRSponsors nicolle_contracting_100 McCain120

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