Plant growth regulators may be useful in lush crops

Plant growth regulators may be useful in lush crops

With feed barley prices pushing historical highs over the past few months, western Canadian growers might be more tempted than ever to push their agronomy packages to achieve maximum barley yields.

Under the right growing conditions, that could make plant growth regulators (PGRs) an investment worth considering, says Sheri Strydhorst, agronomy research specialist with the Alberta Wheat and Barley Commissions.

“These products are meant to mitigate lodging,” said Strydhorst.

“They keep the plant shorter and don’t cause that tall growth, so you won’t have that heavy seed head sitting really high up in the canopy” where it can be laid flat by wind and rain.

“This is a tool for growers to be able to push agronomy in highly productive areas and then manage the lodging piece (with PGRs).”

PGRs are still relatively new to Western Canada so grower experience and performance data is limited.

But researchers are learning more.

In Alberta, Strydhorst did her own PGR product comparisons on barley plots near Barrhead, northwest of Edmonton.

Two PGR products — Moddus and Mainpulator — were applied on AAC Synergy and CDC Copeland.

“We found Manipulator reduced plant height by three centimetres and Moddus by 10 cm,” Strydhorst told The Western Producer.

“We didn’t have a lot of lodging in the trial, but when we did, we found the Moddus improved standability.”

PGR products can be used on spring wheat, durum and winter wheat, as well as barley.

There is limited Canadian data assessing performance on oats.

Before making the decision to use a PGR on barley, growers should keep a few things in mind.

For starters, PGRs are suited for situations where there is excellent soil moisture and where big crop yields are expected.

PGRs are not a good fit for crops growing in dry soil or crops with limited yield potential.

“The labels on both Manipulator and Moddus clearly state: don’t apply to a barley crop that’s environmentally stressed or under stress from waterlogging, drought or nutrient deficiency,” said Strydhorst.

“When you have those external pressures, a PGR is really not recommended. But if you’re in that sweet spot where everything is looking great — the high yield potential is there and the rainfall is timely and sufficient — then that’s the situation where you’d want to consider using a PGR.”

Growers should also keep in mind that the primary benefit of using a PGR is to reduce or prevent lodging and to improve the harvestability.

Because standability is improved, harvest efficiency will be enhanced and grain quality will generally be better due to reduced lodging.

“If you don’t have a crop that’s lodged and sitting down on the ground, you’re going to prevent disease because your (seed) heads are up in the canopy, rather than lying flat on the soil.”

PGRs reduce lodging by limiting a plant hormone called gibberellin, which promotes stem elongation.

However, it shouldn’t be assumed that a plant that uses less water and fewer nutrients on stem development will redeploy those inputs into grain production.

Any potential correlation between PGR use, shorter straw and higher grain yields is not well understood.

“With less stem elongation, there is some redistribution of nutrients, so you can have increased root growth, but that doesn’t happen every single time.”

Growers should also weigh the purchase price of PGR products and application costs, against the potential financial benefits.

For best results, PGRs should be applied in a separate sprayer pass, rather than tank mixed with other products.

The recommended application window for Manipulator and Moddus is between growth stages 31 and 32.

Typically, that recommended application window can last from two to four days, depending on growing conditions.

Additional information on the use of PGR products in barley can be viewed online at

Strydhorst also urged growers to check with grain buyers before using PGR products on barley to ensure compliance with Keep It Clean product advisories.

Manipulator (chlormequate chloride) is currently rated as an “amber” product in Keep It Clean advisories, meaning growers should check with their grain buyers before using the product on feed, food or malt barley.

Moddus (trinexapac-ethyl) does not have any Keep It Clean product advisories or warnings.

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