Take Home Messages
- The first fungicide application (at the start of stem elongation) was the most crucial for protecting the crop and maximising final yield
- When starting soil mineral nitrogen (N) levels are high (240kg N 0–100cm), high N rates are not needed to maximise grain yield.
- With a grain yield of 5.9t/ha, Cyclops outyielded both RGT Planet (4.3t/ha) and Leabrook (5.1t/ha).
- Increased fungicide applications are required to maximise grain yield when sowing disease susceptible varieties early.
Aim
To achieve and derive water limited yield potentials in environments defined by heat, frost and terminal drought during grain fill. Our primary objective is to update management guidelines to achieve water limited yield potentials in Low Rainfall Zone (LRZ) – Medium Rainfall Zone (MRZ) barley.
Background
The new frontier for barley water use efficiency is accepted as 25kg/ha/mm, but this has rarely been demonstrated. Apart from variety selection, recent research has demonstrated canopy management in barley – through the use of fungicides, sowing time, and plant growth regulation – can explain yield responses ranging from 3t/ha to 8t/ha within similar genetics in cooler and milder production environments. These factors have been more important than nitrogen management, particularly on fertile soils and where yield potential exceeds 5t/ha. There may be more scope to close the yield gap in the short to medium term with improvements in disease management, head loss, brackling and lodging control, however this has not been investigated in lower yielding environments.
Paddock Details
Location: Kinnabulla
Crop year rainfall (Nov–Oct): 276mm
GSR (Apr–Oct): 187mm
Soil type: Sandy clay loam
Starting soil N: 241kg N/ha (0–100cm)
Paddock history: 2022 brown manured lentils
Trial Details
Crop type: Barley, refer to Table 4 for varieties
Treatments: Refer to Table 1
Target plant density: 130 plants/m²
Seeding equipment: Knife points, press wheels, 30cm row spacing
Sowing date: TOS1 1 May 2023
TOS2 16 May 2023
Replicates: Four
Harvest date: 10 December 2022
Trial average yield: 5.1t/ha
Trial Inputs
Fertiliser: Granulock Z @ 60kg/ha at sowing
Refer to Table 1 for in crop applied nitrogen rates
Herbicide: Trial managed as per best practice
Insecticide: Trial managed as per best practice
Fungicide: Refer to Table 2 for fungicide strategies
Seed treatment: Standard seed treatment of Raxil and Gaucho, refer to Table 2 for additional seed treatment
Method
A replicated split-plot trial was established at Kinnabulla to evaluate different agronomic strategies and the associated yield gaps. Assessments included lodging scores, head loss assessment, grain yield and grain quality. Two sowing dates were evaluated, an early sowing date (TOS1) and an on time sowing date (TOS2). Each sowing date consisted of eight levels of increasing management applied to three barley varieties
Results & Interpretation
Grain yields varied from 3.2t/ha to 6.4t/ha across the trial in 2023. The highest treatment yield came from a Cyclops treatment, sown early (1 May) with low nitrogen supply (241kg N/ha 0–100cm) and high fungicide intensity (three fungicide applications + extra seed treatment).
Fungicide
Although response to fungicide strategy was not as dramatic as 2022, it was still critical for maximising grain yield in 2023. Under high nitrogen input, Cyclops gave the biggest response to the addition of fungicide at 0.8t/ha while RGT Planet gave the biggest response under the low nitrogen input at 0.7t/ha. Diseases present in the trial included spot form of net blotch (SFNB), net form of net blotch (NFNB), scald and leaf rust. Figure 1 shows the high NFNB infection of RGT Planet and low levels of SFNB and leaf rust in Leabrook and Cyclops at the BCG main field day.
When averaged across sow dates, even the disease susceptible variety RGT Planet (rated Susceptible–Very Susceptible (SVS) to scald, SFNB and NFNB) showed not statistical yield increases above the intermediate fungicide strategy of a single Prosaro application at the start of stem elongation. On average, increasing from no fungicide applications to a single application gave a 600kg/ha yield response. In higher disease pressure scenarios – early sowing and high nitrogen supply provide a larger, more humid canopy conducive to disease infection – high fungicide input was required to maximise grain yield (Table 6). The biggest response still came from the first application of Prosaro with a 760kg/ha response to that application and only an extra 190kg/ha yield response to the additional three units.
Nitrogen
Across all three varieties, there was no significant increase in grain yield from the application of in-season nitrogen (Table 5). Cyclops and Leabrook were unaffected by increasing nitrogen supply when disease was controlled, while RGT Planet saw a yield decrease in response to increasing nitrogen supply which was likely caused by greater lodging and brackling. While not showing yield differences across varieties, increasing nitrogen supply provided a significant increase in crop lodging/brackling (Figure 2).
Canopy Management
Canopy management in association with high input management provided significant increases in grain yield in 2023. A yield response of 840kg/ha to the application of PGRs was seen in the lodging susceptible variety Leabrook.
Figure 2 shows how the use of PGRs and canopy defoliation both significantly reduced crop lodging. It also shows increasing fungicide intensity helped improve straw strength and reduced lodging.
There was no yield penalty from canopy defoliation (grazing) when the crop was sown on time, however when sowing was delayed, there wasn’t sufficient time for the crop to recover resulting a yield penalty (Table 5). Canopy defoliation also helped reduce disease pressure (Figure 3), especially early in the growing season.
Hay Quality
Choice of variety provided the biggest yield differences, with Cyclops yielding 5.9t/ha, Leabrook yielding 5.1t/ha and RGT Planet yielding 4.3t/ha. Time of sowing influenced yields of each variety differently (Figure 4). Cyclops yielded better at TOS1 compared to TOS2, while RGT Planet yielded highest at TOS2, and Leabrook was largely unaffected by sowing date.
Management strategy and variety choice also provided differences in grain quality and resulting bin grade at grain receivals (Table 7). Cyclops is currently undergoing malt accreditation so can only be delivered as feed barley (BAR1 or BAR2), while RGT Planet and Leabrook are both accredited and can be delivered as malt (MALT1) if they meet specifications. Across all varieties, increasing nitrogen supply resulted in an increase in grain protein which was often too high for malt specifications, except when the treatment was grazed. However, grazed treatments of RGT Planet and Leabrook did struggle with low test weight and still didn’t meet specifications. RGT Planet struggled with test weight across most treatments and had issues with retention and screenings where disease infection wasn’t controlled.
Commercial Practice and On Farm Profitability
Trial results from 2023 paint a slightly different picture to the results achieved in 2022 (see 2022 BCG Season Research Results). The high nitrogen balance at the start of the season was an important factor. With 241kg N/ha (0–100cm) at the beginning of the season, the addition of nitrogen during the season resulted in yield and grain quality losses in RGT Planet, which in turn reduced profitability at the end of the season for this variety. Despite high disease pressure, particularly NFNB, fungicide strategy was less important in 2023 than 2022. A single fungicide application at the beginning of stem elongation in 2023 was enough to reduce disease levels to a point where they didn’t affect grain yield. Choice of variety was imperative for closing the yield gap in 2023, with RGT Planet sown on 1 May yielding 4.24t/ha and Cyclops sown on the same date yielding 6.05t/ha.
Results from this season continue to support the fundamental principles learnt in 2022: that building the right canopy for a high yielding barley crop starts with selecting the right sowing date. This helps ensure the crop flowers in the optimum window – when the risk of frost, heat and drought is low – and when the critical period is best aligned with cool and sunny conditions. Opting for the correct level of nitrogen supply also helps build a canopy that can produce a high yielding crop, alongside choosing the correct fungicide strategy to maintain green leaf area to maximise light interception. The 2023 trials showed the optimum nitrogen supply for grain yield was achieved through high soil fertility from the brown manured pulse crop in the previous year. This optimum nitrogen supply of about 240kg N/ha was the same as in 2022, however the starting balance in 2022 was lower, and in-season applications were needed to achieve this supply figure.
Fungicide applications could have been successfully reduced in 2023, with no further yield increases above a single application in most scenarios. Accurate timing was still crucial as the beginning of stem elongation marks a critical growth period for barley fungicide management. At this growth stage the important yield contributing ‘money leaves’ have started to emerge (F-2, F-3) in barley. The timing of this application also coincided with an improved season outlook compared to Autumn seeding time. Additional applications can be made if the season dictates, as was the case in 2022. Inversely, if the season turned dry, further applications may be re-evaluated.
In 2023, positive yield responses to the use of PGRs were observed. The need for PGRs was likely due to the high nitrogen supply of 310kg N/ha and the resulting bulky canopies that experienced lodging and brackling. Split application of PGRs, at GS31 and GS33-GS37, reduced lodging and brackling so it did not limit grain yield. Reducing nitrogen supply and increasing fungicide applications also decreased crop lodging and brackling. Note that yield responses to PGRs can be inconsistent, and their use should be considered carefully as, in some circumstances and environments, crop damage can occur.
References
Price T., Poole N., Bennett B., and Porker K., 2023, 2022 BCG Season Research Results, ‘Barley Management Options to Close the Yield Gap and Reduce Pre-Harvest Losses’ pp 57–62
Acknowledgements
This research was funded by the GRDC as part of the National Grower Network project ‘Barley management options to close the yield gap and reduce pre-harvest losses’ (FAR2204-002SAX).
