AUSVEG collaborated with a diverse range of industry experts to deliver a tailor-made session to address the needs of the region, which were identified through the onion extension project, Accelerating the adoption of best management practices for the Australian onion industry.

Bruce Scott, plant nutrition and fertiliser specialist for Campbells Fertilisers, spoke to growers at the workshop and emphasised the critical role that soil health plays in achieving optimal crop yields.

Myalup soil is quite unique; the area’s soil is around 94 percent sand and 6 percent silt. Sandy soils are well-known for having low water and nutrient-holding capacity, and are often prone to erosion by wind. This is exacerbated by a lack of organic matter in the soil. This presents a number of challenges for growers in the region.

Some protective measures to combat soil erosion include minimum tillage, implementing cover crops, strip cropping, rotating crops, and establishing windbreaks.

The low nutrient-holding capacity of sandy soils means the incorporation of organic amendments is relatively short-term. The use of stubble retention can be a way to retain nutrients and organic matter in the soil. Additionally, humic acids and seaweed-based products can stimulate the roots of the onion crop, this aids in nutrient uptake and the ability of the plant to hold nutrients and moisture in the root zone for longer, improving nutrient use efficiency.

Bruce highlighted the importance of understanding your soil.

“It is essential to understand the chemical properties of your soil through a soil analysis,” he stated. “It is also important to understand the physical and biological properties, which can be done through visual assessment and biological soil analysis.”

Bruce passed around an example soil analysis that was conducted on a farm in the region in 2023. The soil analysis showed low levels of nitrogen, potassium, boron, magnesium and iron. These elements are macronutrients and micronutrients essential for onion and vegetable production.

It is crucial to supply these nutrients, and the timing of their application should be based around nutrient uptake patterns in onions across the crop’s growth stages.

In the initial stage of planting, compound fertilisers can be utilised to enable a longer lasting release of nutrients to the crop. Additionally, coated compounds are now available on the market, which are much less vulnerable to leaching. To get the best out of your nutrient inputs, fertigation is an ideal way to supply small, frequent doses to meet the requirements of the crop as it develops.

Nitrogen is essential for leafy growth and bulb development, and a lack of nitrogen will severely suppress growth. On the other hand, excessive nitrogen can produce plants that are more susceptible to frost and disease. Additionally, over-application of nitrogen is likely to cause issues in storage and export, as bulb softening and rot can occur.

Phosphorus is essential for root development, and is therefore required at the establishment stage of onion development.

Potassium aids in optimal plant to water relations, and crop energy reactions, influencing plant growth and metabolism. Applying potassium during the bulb development stage increases bulb size and quality.

Boron plays a crucial role in root development and in the structural development of the whole plant, in a similar way to calcium. Optimal boron levels promote nutrient uptake, water regulation, and overall plant health. However, it is important not to exceed the recommended level of application as boron can be toxic in onions, Bruce cautioned the workshop attendees.

Magnesium and iron are two of the elements that are most important in chlorophyll production, which aids in the photosynthesis process of the plant and ensures good leaf production and healthy crop development.

The workshop also heard from Ivor Gaylard, Chief Operating Officer and founding director of SWAN Systems, who addressed the importance of optimising water-use efficiency, and the use of irrigation technology to monitor soil-water relations.

“Good irrigation management has a significant impact on your bottom line,” Ivor stated. “Get the infrastructure right first, then schedule your irrigation applications to get the best results.”

Ivor explained how proper irrigation management is essential for maximising onion yields, as under-irrigation can hinder photosynthesis and lead to issues such as split or multiple bulbs. Conversely, over-irrigation can lead to disease issues and skin damage, ultimately reducing marketable yield.

Planning irrigation requires careful consideration of various factors, including soil properties, root depth, crop growth stages, weather patterns, water availability, and the timing of fertiliser applications.

Utilising tools such as soil moisture probes can help identify a number of factors, including what happens to soil water during the year, the rooting depth of the crop, the effect of rain events, and the effect uncontrolled weeds can have on stored soil moisture, as well as temporal variations present in stored soil moisture across a paddock. This knowledge allows growers to make informed decisions around irrigation scheduling, in order to match irrigation to crop water demand.

Stephanie Carstairs of Planfarm

Stephanie Carstairs, project manager of the National Vegetable and Onion Benchmarking Program (also known as Level Up Hort) and horticultural consultant for Planfarm, presented findings from the program’s recent benchmark report.

Stephanie provided a snapshot of where the Australian vegetable and onion industries are positioned, and highlighted some of the strengths and challenges facing the industry at present.

“The most profitable vegetable and onion growing businesses generate higher profits per hectare, despite higher input costs,” Stephanie noted.

The targets established in this benchmarking report are based on industry standards and are published as a guide to setting industry targets to achieve a profitable and globally-competitive vegetable industry. The report can be downloaded at leveluphort.com.au

Camilla Humphries, consultant with RM Consulting Group, discussed the Soil Wealth ICP project, which focusses on integrated crop protection strategies within the vegetable and melon industries.

Camilla shared several strategies for enhancing soil health, such as implementing cover crops, adequate crop rotations, and improving soil structure through compost use.

Camilla also highlighted the importance of integrated pest and disease management, asserting that these practices not only bolster crop health but also yield economic benefits.

The soil health and irrigation management event held for the Myalup onion growers was a great opportunity not only for growers to talk with industry bodies and experts but also for growers to talk with other growers. Building grower-to-grower relationships not only benefits the individuals but the entire region.

The onion extension project is also hosting workshops on soil nutrition and onion storage in the Lockyer Valley, and another on ryegrass resistance management and mechanisation in Tasmania, both before the end of 2024. Check the AUSVEG communication channels for more information.