Plant Growth Regulator use in Barley

Take home messages

• Plant growth regulator (PGR) use increased barley yields in a year of high rainfall.
• Combining PGR applications with fungicides has the greatest benefit on yield.
• Two applications of PGR at GS31 and 37 increased yield by 14.4 per cent above standard practice.

Background

Barley varieties have different characteristics and growth habits which can influence a varieties risk to lodging, brackling (breaking at the top node) and head loss. In seasons with high yield potential, the risk of barley losses increases due to heavy head development relative to plant height, stem strength and subsequent lodging.

The use of plant growth regulators (PGR’s) is one strategy available to mitigate these losses. However, there is limited experience with their use in the Wimmera.

Moddus Evo^® is one PGR registered for use in barley. It is composed of a chemical compound that inhibits the plants synthesis of gibberellin, a plant hormone that regulates growth and influences stem elongation. When production of gibberellin is limited, stem growth is retarded and the stem wall thickness is increased.

Previous work by BCG in recent dry seasons has shown that a reduction in plant height was greatest when PGR application occurred as a single late or split application – not an early application (Angel 2014). In 2013, PGR’s were found to suppress plant height and generate a yield benefit in the Wimmera (McClelland 2013).

This research aims to assist with the management of barley varieties in higher yielding seasons.

Note: Trials were carried out at Longerenong and Lubeck but are discussed separately due to different treatments and protocols at each site.

Trial 1. Longerenong – barley response to PGR

Aim

To determine if the use of the PGR Moddus Evo^® and fungicides mitigates lodging and head loss in barley.

Paddock details

Trial details

Trial inputs

Method

The trial was sown using a complete randomised block trial design. Assessments included lodging scores, disease scores, plant height assessments, plant length assessments, and grain yield and quality parameters.

The trial focused on the relationship between Moddus Evo and fungicides at various timings to improve harvestability, yield and quality (Table 1). To maximise yield, large amounts of urea were applied, aiming to reach a yield potential of 8t/ha. Compass and Scope CL barley were chosen for this trial due to susceptibility to head loss and lodging.

Table 1. Spray treatments applied to Compass and Scope CL barley varieties.

Results and interpretation

There were no differences in stem length between the spray treatments, however there were
differences in actual crop height between varieties and treatments. Moddus Evo^® was effective in helping Scope CL stand taller, with an additional benefit observed when applying fungicides with the PGR to help straw strength.

Conversely, Compass did not respond in the same way with all treatments lodging severely (Figure 1). This may be due to the timing of the second application at GS39, compared to Scope CL at GS37.

Figure 1. Mean stem length (cm) and actual height (cm) measured before harvest. The data labels on the overlayed dark grey bars indicate the percentage decrease from stem length (maximum height) to actual height. Variety x timing stats: P=0.001, LSD=10.7cm, CV=11.6%.

Differences in grain yield between the spray treatments were observed, but there was no interaction with variety (Figure 2).

Disease was an influencing factor in the untreated fungicide plots (P<0.001). Scald was present across the trial late in the season with the untreated fungicide treatments experiencing 73 per cent leaf area affected. All plots treated with fungicide had below 29 per cent leaf area affected. Applying fungicide or a single application of Moddus Evo^® did not increase yield from the untreated control.

Two applications of Moddus Evo^® without fungicides had a small increase in yield from the control. Combinations of Moddus Evo^® with fungicides had the largest yield response from the untreated barley, increasing yield by up to 1.3t/ha. When adding the PGR with fungicides a multiplicative effect was observed, increasing by more than the individual treatments added together.

The addition of two applications of Moddus Evo^® to fungicide increased yield by 0.97t/ha. The results suggest adding fungicide with a PGR had an additive effect on yield in these conditions.

Interestingly, there was no significant yield difference between varieties, indicating that the severe lodging experienced by Compass did not have an adverse effect on yield.

Figure 2. Mean grain yield (t/ha) of the different treatments. Spray treatment stats: P<0.001, LSD=0.36t/ha, CV=5%.

Grain quality was affected between both varieties and spray treatments. For all quality parametres except protein, adding fungicide was crucial for maintaining good quality (Table 2). Screenings and retention were also improved through the use of fungicides and improved even further through the addition of Moddus Evo^®. Overall, Compass had lower screenings and larger retention than Scope CL, potentially due to a naturally larger seed size.

Test weight improved with the use of fungicides and was further improved by the use of Moddus Evo^® in conjunction with fungicides. There was no significant difference between varieties for test weight.

No treatments reached malting 1 specifications. The closest treatment was two fungicides with two applications of Moddus Evo^® in Compass. Specifications were not met as protein was too high.

Table 2. Grain quality parameters for the Longerenong trial.

Trial 2. Farmer demonstration – Lubeck

Aim

To determine if PGR on a paddock scale has an effect compared to standard farmer practice on final grain yield in Compass barley.

Paddock details

Trial details

Trial inputs

Method

A 22ha paddock of Compass barley was managed by a farmer using standard practice. Moddus Evo^® was applied as a single application to four boom widths down the length of the paddock using a water rate of 100L/ha whilst the remainder of the paddock was left untreated.

Visual observations were made before and at the time of harvest. The paddock was yield mapped and results were analysed using a paired t-test both in and outside the PGR block. The yield was analysed from five header strips either side of the plus and minus strip.

A single sample t-test was conducted to determine if a statistically significant difference existed between barley yields from a PGR treated area and the neighbouring non-treated paddock.

Results and interpretation

The average Compass yield across the 1.2km long paddock was 5.78t/ha. The application of Moddus Evo^® resulted in a yield of 5.92t/ha, a 0.14t/ha yield increase (P=0.002). In the northern half of the paddock, more variation in yield was observed. This could be attributed to changes in soil type and water logging. The two areas were assessed but there was no difference, with the PGR being higher yielding in both sections.

Commercial practice

At Longerenong, barley showed the greatest yield increase when two applications of Moddus Evo^® were used in conjunction with fungicides at GS31 and GS37. Fungicides did not seem to have a particularly large effect on yield, but had a large effect on quality. The addition of two PGR’s to the fungicide increased yield by 14.4 per cent. Disease was a significant factor in these results.

In the farm demonstration trial at Lubeck, yield increased by 2 per cent with the addition of Moddus Evo^®. The average yield of the trial at Longerenong was 6.95t/ha where the Lubeck trial yielded 5.85t/ha. The difference between the Longerenong trial and the farm demonstration at Lubeck most likely relates to the amount of urea applied. Moddus Evo appeared to have a greater influence into the Longerenong trial where maximum yield potential was trying to be obtained. Further investigation into whether the amount and timing of nitrogen has an effect on PGR performance to achieve maximum yield and quality is required.

Over the previous three years of research, PGR’s have returned varied responses in yield which has been highly dependent on seasonal conditions. The 2016 season was one out of the box where there were many advantages in the application of PGR’s, due to a Decile 8 rainfall year and subsequent large and heavy crops. The timing of PGR application is also an important factor to consider, there earlier it is applied the greater influence it has on stem strength and therefore lodging prevention.

Farmers need to carefully consider the use of PGR’s in their farming system and weigh up the agronomic versus economic consequences, particularly in a year with poor grain prices.

On-farm profitability

In a decile season like 2016, the use of Moddus Evo^® in Compass barley proved the right decision agronomically. However, it was not a positive economic decision as demonstrated in the Lubeck trial.

At Lubeck, the yield benefit of applying the PGR was 0.14t/ha across the various paddock strips which equates to an additional $19.53/ha based on feed barley price at Dooen of $139.50. The cost of applying the Moddus Evo^® was approximately $40/ha, creating a loss of $20.53/ha. If selling at harvest time in 2016, an increase of 0.29t/ha would had to have been made to cover the cost of applying the PGR.

In the Longerenong trial situation, an increase of 14.4 per cent over normal practice (two fungicides) was achieved with two applications of PGR, in this situation the result was an additional $95/ha.

References

McClelland T., 2013, 2013 BCG Season Research Results, ‘Good things come in small packages: plant growth regulators’ pp. 86-90.

Angel K., 2014, 2014 BCG Season Research Results, ‘Plant Growth Regulators in Scope CL Barley’ pp. 39-44.

Acknowledgements

This research was funded by Syngenta. BCG would also like to thank Mayo Park Farms for sharing their paddock data.