Where lodging constrains barley yield potential, plant growth regulators can help to mitigate this

Plant growth regulators (PGRs) may have a place in northern New South Wales cropping systems, increasing grain yield in barley crops – especially crops at risk of lodging.

AMPS Research, the Tamworth-based grower-owned agricultural services group, explored the role PGRs could have in reducing barley lodging. Lodging is a risk in warmer areas of the northern grains region.

It can constrain high-yielding dryland barley production.

Head research agronomist Matt Gardner says using PGRs is one way to address the issue.

They can be an effective tool to minimise lodging. Under the right conditions, PGRs can also significantly increase net returns – without taking into account reduced harvesting costs.

However, trials undertaken in a GRDC National Grower Network (NGN) project showed yield responses vary greatly depending on the variety.

“Leabrook was the most responsive and Maximus CL was the least responsive,” Mr Gardner says. “Both varieties are quicker varieties, but Leabrook has a high susceptibility to lodging.”

Trials

Seven trials were undertaken in northern NSW across 2022 and 2023. Seasons varied, with more favourable conditions in 2022.

Four varieties – Leabrook, Laperouse, RGT Planet and Maximus CL – were selected to represent a range of lodging susceptibilities.

The PGRs tested were Moddus® Evo (250 grams per litre trinexapac-ethyl) and ethephon (Promote® Plus 900, 900g/L ethephon).

In 2022, three trials assessed Moddus® Evo and ethephon and a range of use patterns.

Following high levels of lodging in 2022, four trials in 2023 quantified the impact of PGR treatments on different varieties, times of sowing and nitrogen levels.

Results

The results varied but were positive. “If seasonal conditions, variety and PGR treatment line up then positive financial returns are achievable with reduced risk,” Mr Gardner says.

AMPS Research head research agronomist Matt Gardner. Photo: Nicole Baxter

As an example, he says Moddus® Evo was applied to Leabrook at GS31. In this case, partial gross margins increased from $153 per hectare to $193/ha in 2022.

Under more marginal conditions in 2023, the change in partial gross margin ranged from $31/ha to $179/ha. “Unexpectedly, there was still a large benefit observed in most situations, in what was a really tough season.”

Another example is applying Moddus® Evo to RGT Planet at GS37. In this case, partial gross margins increased from $164/ha to $238/ha in 2022. However, under lower-yielding conditions in 2023, the change in partial gross margin decreased. It ranged from $31/ha to $179/ha.

“Growth regulators had a much larger grain yield response in 2023, in the absence of lodging, which still made it a profitable decision.”

The other PGR tested was ethephon. Mr Gardner says that while this is substantially cheaper, it carries a higher production and financial risk.

“In 2022 and 2023 applications at GS41 and GS45 decreased partial gross margins in more than 80 per cent of cases. Large increases in partial gross margin only occurred under high-yielding, lodging-susceptible conditions for Leabrook.”

PGR use constraints

When dealing with barley lodging, many growers and advisers in the northern region do not turn to PGRs, Mr Gardner says. This is because of variable lodging, yield responses, and financial returns. Three key factors drive this variability.

1. Variable responses to PGRs exist even in experimental conditions and must be factored into PGR programs.
2. PGR decisions must be made early in the season (during tillering) when the final yield, lodging susceptibility, and the likely response to a PGR are uncertain.
3. On-farm logistics mean PGRs are often applied late and the maximum benefit is not achieved.

He says other factors affect adoption too, including:

• product cost
• ability to execute on time due to logistics and trafficability
• low confidence in the spring forecast and thus the forecast yield
• yield penalties
• the difficulty of assessing PGRs’ cost–benefit ratio early in the season.

“As a result, advisers and growers favour using agronomic factors to reduce lodging risk. This includes variety and paddock selection, nutrition management and time of sowing.

“While positive results have been achieved at paddock scale, PGR adoption remains limited to situations where other management strategies have been insufficient to prevent a major lodging event. The 2024 season in northern NSW was an exception and gave conducive conditions for lodging in barley.

“We have seen more widescale use of PGRs in barley. It is hoped that their use as a tool becomes broader in the right situations.”

Table 1: Should a PGR be applied this season?

Before planting or early in the growing season assess lodging risk and decide early if a PGR may be required. Consider the factors below. If the answer is YES to 3 or more factors, discuss PGR options with your adviser.

AMPS is developing a Decision Support Tool called ‘Lodging & Plant Growth Regulators (PGRs) in Dryland Barley’.
Source: AMPS

Resources: 
Read more in GroundCover^TM story The NGN delivers large gains to growers

Why is lodging an issue in the northern region?

Lodging risk constrains high-yielding dryland barley production in northern NSW.

Lodging susceptibility is driven by rapid growth in early crop development through to head emergence and is exacerbated in high-yielding conditions.

Lodging causes losses in crop production through reduced water and nutrient movement and reduced translocation of stored carbohydrates from the stem to the head. Lodging can also reduce grain quality and increase harvest losses and harvest costs.

What can be done to minimise its impact?

Advisers and growers tend to favour agronomics to reduce lodging risk. This includes variety and paddock selection, nutrition management and time of sowing.

Table 2: Varieties’ partial gross margins (additional gross income minus PGR product and application cost) for PGR-treated barley.

Nil PGR gross income ($/ha) shows the gross income for nil PGR; PGR columns show the difference in the partial gross margin from the nil PGR ($/ha)*

* Assumptions: barley $280/t; ethephon $10/L; Moddus® Evo $75/L; application cost $12/ha. PGRs Ethephon (900g/L ethephon) and Moddus® Evo (250g/L trinexapac-ethyl).

GS – growth stage.

Source: AMPS Research

What is a PGR?

Commercial plant growth regulators (PGRs) can be used to reduce crop height and lodging and increase grain yield.

Those used in Australia either block the biosynthesis of plant hormone gibberellin (Moddus® Evo) or increase ethylene (ethephon) concentration, which reduces internode length and decreases plant height.

PGRs may increase the proportion of dry matter that is partitioned to yield. They may also increase root growth, improving water and nutrient extraction.

However, previous research indicated yield responses in the region were highly variable.

Variable lodging and yield results make it hard to predict PGRs’ financial benefit.

Low confidence and use patterns mean few growers and advisers apply or recommend them. Application is often reactive rather than proactive. This results in later-than-ideal application timing and lower product efficacy.

AMPS Research has explored the role PGRs could have in reducing barley lodging with trials undertaken in a GRDC National Grower Network (NGN) project. The objective was to provide information that increases confidence in using PGRs.

Economic analysis

Economic analysis shows that PGR use can be worthwhile. Table 2 shows an average of all varieties’ partial gross margins across 2002 to 2023.

What is the NGN?

GRDC’s National Grower Network (NGN) is an open community of growers and grains industry stakeholders that was established in 2021.

Figure 1: NGN projects across the northern region.

Source: Kynetec

Engaging directly with stakeholders through forums, the NGN helps GRDC develop locally relevant research, development and extension (RD&E) investments.

This might be through short-term, local investments to address a specific issue, by informing large investments in GRDC’s broader portfolio, or ensuring relevant national projects include local RD&E  when the need is identified.

Its key features are to:

• support meaningful engagement with growers, advisers and other industry stakeholders
• improve understanding of local issues
• assist in the development of locally relevant investments that are timely and have on-farm impact.

GRDC senior regional manager – north Rebecca Raymond says engagement with growers through the NGN process improves how GRDC delivers RD&E across its investment portfolio.

The NGN process also provides more flexibility to respond to local issues.

For example, in July 2024 at an NGN forum in Bellata, NSW, growers raised concerns around correct disease identification so they can implement effective management strategies.

GRDC consulted industry experts then went to market to engage a service provider to deliver disease identification workshops and supporting material.

A contract was signed earlier this year with workshops planned in the second half of 2025.

More information: GRDC National Grower Network.