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PGRs for malting barley? Maybe

Research suggests plant growth regulators should be considered as a risk-management tool in fields with high yield potential

Lodging presents a much higher risk of yield and quality reductions and economic losses if barley can’t be sold for malting.

[UPDATED: April 12, 2021] Lodging is the enemy of barley producers, especially if they’re hoping for a malting premium. It’s prompted some producers to get out of barley altogether. Others are turning to plant growth regulators (PGRs) to help cut their losses.

Sheri Strydhorst, a research scientist at the University of Alberta, says lodging is a “huge, huge problem” for producers in highly productive areas.

“We farm at home here and where we’re planning to grow barley, because of the headache it causes at harvest, we’re willing to give PGRs a try at the field scale.”

Lodging isn’t just a harvest-time headache due to the need for reduced speed and the inefficiency of having to swath rather than straight-cut a field. It also presents a much higher risk of yield and quality reductions and economic losses if barley can’t be sold for malting.

Strydhorst’s work focuses on how different varieties respond to different agronomic practices. In 2013 she began studying the utility of gibberellin-inhibiting PGRs on wheat and barley across Alberta’s growing regions.

Gibberellins are a group of plant hormones that stimulate stem elongation, germination and flowering. Gibberellin-inhibiting PGRs are designed to halt that elongation so plants develop a thicker, sturdier base and are less prone to lodging.

There are two gibberellin-inhibiting PGRs registered for cereals in Western Canada — chlormequat chloride (Manipulator) and the newly registered trinexapac-ethyl (Moddus) from Syngenta.

Strydhorst says a new project led by Laurel Thompson, a research scientist at Lakeland College, will look at the efficacy of Moddus when combined with different rates of nitrogen and different cultivars.

“What we saw in the most recent field trials with Moddus on barley was a 4.2 per cent yield increase over an untreated control in responsive site years. That was occurring 50 per cent of the time — some years we got nothing and some years we got that increase. If you do the math, it’s not going to cover the cost of that PGR. What growers have to think about is using this as a risk-management tool.”

Strydhorst says the conditions that contribute to lodging include using a variety prone to lodging, high N fertility, heavy rainfall and a productive growing season. Even if extra yield does not cover the cost of the product and its application, there could be possible time savings at harvest if the PGR improves standability.

“If the stars align and that crop is meant to lodge this will not prevent that, but it might lessen or delay the lodging and help them get through harvest,” she says.

Efficacy data

Syngenta technical lead Randy Retzlaff says that in keeping with market preparation guidelines, the company tested Moddus for three years in farmer research authorization trials to supplement its small-plot data. Participants were provided with up to 80 acres of Moddus to apply on part of a field where they’d normally be concerned with lodging, leaving the balance untreated.

In 41 barley trials (roughly half of which were feed varieties and half malt), the product averaged five-bushels-per-acre yield maintenance versus the untreated parts of the field, Retzlaff says.

“Where there was more lodging happening or when there was more moisture, in some cases those results were as high as 17 bushels per acre. The nice thing is… the more lodging is a concern, the more a PGR can help.”

In a study on the effects of PGRs on malting barley in Western Canada, Agriculture and Agri-Food Canada research scientist Breanne Tidemann found that trinexepac reduced plant height and kernel weight and showed the largest number of lodging reductions, although none of the products tested (trinexepac, chlormequat and ethephon or 2-chloroethylphosphonic acid) affected yield or grain protein.

Trinexepac reduced lodging in five out of 14 comparisons to the control (36 per cent), but Tidemann says the scale of lodging reductions for all three PGRs studied was “fairly minor” as a result of PGR application.

“Results from the present study suggest that PGR-related crop shortening is not a guarantee that lodging will be reduced,” Tidemann writes in the study. “Effects of PGR on lodging were variable and not always predictable, nor were they always effective. In some heavier lodging environments, trinexepac provided the most benefit.”

“Producers need to have appropriate expectations that PGRs do not have the same consistent efficacy as other plant protection products such as herbicides,” she concludes.

Application tips

Retzlaff and Strydhorst agree that trinexepac isn’t for every producer.

“The long-term solution is really improved genetics, but we’re not there yet. In the meantime, this is a potential tool to get us part way there in some years,” Strydhorst says. If producers decide to use it, she recommends starting with a small test strip to see how the product performs on their farm.

Some cultivars are more responsive than others, she says. In 2018, her team compared Copeland and Synergy malting barley and found that Copeland had more height reduction with PGR applications versus Synergy, but Copeland doesn’t necessarily respond better, Strydhorst says. If a cultivar has poor genetic resistance to lodging, a PGR will not prevent lodging but may lessen or delay its onset.

Retzlaff says Moddus has a wide application window and can be applied right up to growth stage 39, but the ideal time to apply the product is around growth stage 30-32, when the plant is at the five- to six-leaf stage and there are one to two tillers. “This is typically when the gibberellin production is starting to peak in the plant,” he says.

Strydhorst’s team has tested gibberellin-inhibiting PGRs outside the recommended window and found they were less effective, although no crop injury was reported.

Optimal temperatures for PGR activity are above five degrees Celsius, she says.

PGRs should not be applied when the crop is under stress, such as drought or excess moisture or heat, Strydhorst says. If drought is affecting the crop in June, lodging is unlikely and PGR application can be avoided, so producers should wait as long as possible to make application decisions.

As always, producers should discuss application of trinexepac or other PGRs with their buyers to confirm they can sell treated grain.

*Update: the featured image that previously ran with this story was incorrectly identified. We regret the error.

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Julienne Isaacs

Julienne Isaacs is a Winnipeg-based freelance writer and editor. Contact her at [email protected]

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