Take Home Messages
- Additional N supply and increased fungicide intensity were more important than cultivar and PGR application for achieving high yields in 2022.
- Delaying sowing and increasing the level of agronomic management significantly boosted barley grain yield in a good season like 2022.
Aim
To achieve and derive water limited potential yields 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) and Medium Rainfall Zone (MRZ) barley.
Background
While it is assumed the new frontier for water use efficiency (WUE) in barley is 25kg/ha/mm this has rarely been demonstrated. Outside of 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 of 3–8t/ha within similar genetics in cooler and milder production environments. These factors have been more important than nitrogen management, particularly where yield potential exceeds 5t/ha on fertile soils. There may be scope to close the yield gap in the short to medium term with improvements in disease management, head loss, brackling and lodging control in lower yielding environments, particularly in better seasons when moisture stress is less of a limiting factor for yield potential.Â
Paddock Details
Location: Nullawil
Crop year rainfall (Nov–Oct): 497mm
GSR (Apr–Oct): 384mm
Soil type: Sandy clay
Starting soil N: 77kg N/ha
Paddock history: 2021 Lentil
Trial Details
Crop type: Barley, refer to Table 4 for cultivars
Treatments: Refer to Table 1
Target plant density: 130 plants/m²
Seeding equipment: Knife points, press wheels, 30cm row spacing
Sowing date: TOS1 4 May 2022
TOS2 20 May 2022
Replicates: Four
Harvest date: 6 December 2022Â
Trial Inputs
Fertiliser: Refer to Table 1 for applied nitrogen rates
Herbicide: Trial managed as per best practice
Insecticide: Trial managed as per best practice
Fungicide: Refer to Table 2
Seed treatment: Refer to Table 2
Method
A replicated split-plot trial was established at Nullawil to evaluate different agronomic strategies and the associated yield gap. Assessments collected include NDVI, lodging scores, head loss assessment, and grain yield and quality. In this paper only grain yield has been considered.
Two sowing dates were evaluated: an early sowing date (Time of sowing (TOS) 1–4 May) and an on-time sowing date (TOS2–20 May). Eight levels of increasing management were applied to three barley cultivars for each sowing date.
Results & Interpretation
Grain yield varied from 3.6t/ha to 6.9t/ha as a result of management strategy (Table 5). Highest grain yield was achieved when disease was controlled, and higher N rates were used at both times of sowing.
Fungicide
At both times of sowing, the biggest yield response was seen by increasing fungicide intensity. Yield response to fungicide ranged from 0.5t/ha from a single application to up to 2t/ha when four fungicide units were applied. Crops were more responsive to fungicide at the earlier time of sowing and under high nitrogen management. Both these management strategies create a bigger crop canopy which favours disease development and requires a more intensive fungicide strategy to protect potential yield. Early season disease was mostly spot form of net blotch, but later season observations during grain fill indicated leaf rust infection was high and the probable cause of such significant yield responses to fungicide and brackling differences (data not shown).Â
Nitrogen
In general, a significant yield response was recorded when N rates were increased from 60kg N/ha to 160kg N/ha. Yield response to additional nitrogen ranged from 0.2t/ha (not significant) to more than 1t/ha where higher inputs of fungicide were combined. The yield responses to additional N were reduced where disease wasn’t controlled and increased where fungicide intensity was increased.
Canopy Management
At both times of sowing, there were no yield benefits to applying any level of canopy management interventions (PGR application or mechanical defoliation, simulated grazing). When associated with high nitrogen input and good disease management, there was no yield loss to simulated grazing at the early sowing date.
Cultivar
RGT Planet was the highest yielding cultivar at both times of sowing, yielding 5.34t/ha at TOS1 and 6.33t/ha at TOS2 (Figure 1). All cultivars yielded higher when sowing date was delayed, with an average increase of 0.75t/ha.
Commercial Practice and On Farm Profitability
Trial results from 2022 show what can be achieved in cooler seasons when yield potential is not constrained by soil moisture stress. In 2022, the decisions that resulted in the greatest gap between yield potential and realised yield were those taken on disease management. The importance of protecting the upper portion of the crop canopy to maintain light interception and protect yield was evident in 1t/ha yield losses that occurred with a sub-optimal single spray program and 2t/ha yield losses when no disease management was applied. An intensive fungicide strategy of three foliar applications, to protect key leaves and leaf sheaths of the canopy at GS31, GS39 and GS59, is typically the prerequisite for securing high yields in the southern high rainfall zones of Australia. This trial illustrated the same management strategies can be employed during better seasons in lower yielding environments. An intensive strategy was required to maximise yield, although a single application at GS39 to GS49 still gave significant protection of the upper canopy resulting in almost 1t/ha yield under high N management, which is still significant.
Building the right canopy for a high yielding barley crop starts with selecting the right sowing date. This needs to ensure the crop flowers during the optimum window when the risk of heat, frost and drought is low, and when the critical period for setting yield potential is best aligned with cool and sunny conditions. Choosing the correct level of nitrogen supply to match the rainfall decile builds a correct sized canopy for producing a high yielding crop in years with better spring rainfall deciles. The data suggests more N than district practice is needed to ensure yield potentials are met in seasons like 2022. While this was achieved with applied N, a more long-term approach would aim to maintain soil fertility and organic matter using pasture or legume phases, crop residues and limited tillage.
No significant yield response was seen from the use of PGRs in this trial, but they can also be an important factor for protecting yield potential in weaker strawed cultivars and through improving harvest logistics, where large acreages reduce the timeliness of harvest. The application of growth regulators, combined with good disease control and timely harvest, ensures pre-harvest yield losses are reduced, particularly in barley where head loss due to brackling can be problematic.
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).
