Onions grow best in deep, well-drained, fertile soils. The soil should not be prone to waterlogging and have good nutrient retention. We recommend not using soils with stone contents greater than 5% for tillage and harvesting.

Growing onions is suited to flat or gently rolling whenua. This is to help with the access and operation of machinery. We recommend less than 3-7 degrees slope due to increasing erosion risk and machinery requirements.

Onions need a soil depth of at least 60 cm (highly suited) and 45-60 cm (suited) to grow well. Their shallow root system absorbs nutrients and water in the upper soil layers. We recommend that other crops be grown in rotation and suggest a deeper soil than the rooting depth of 25 cm.

For good onion growth and yields, various nutrients are required. This includes:

• Phosphorus - to stimulate root growth
• Potassium and sulphur - to contribute to the bulb yield and quality
• Nitrogen - carefully managed to achieve high yields
• Boron, iron, magnesium, and zinc - in smaller quantities to produce premium bulbs.

It's important to test your soils before planting your crop. Many companies offer this service. This will help you understand the current fertility of your block and nutrient requirements. Optimal soil pH is greater than 6.

Soil safe Aotearoa

In Aotearoa, onions are usually planted in winter/early spring between June and September. However, this depends on where in the country you are located, for example in Canterbury planting happens in early Sept. They need temperatures above 15.5°C for bulbs to form and temperatures within 21 - 27°C for ideal for good growing conditions.

Onions need 3 or fewer days of rainfall within 7 days at harvest (1-Jan to 30-Mar). Too much rain can lead to rot and too little rain can affect the growth of plant shoots and bulbs.

At harvesting, onions need at least 5 days to completely dry to prevent rot.

If you're thinking about growing onions on your whenua, check your region's rainfall and rain intensity. This is important while your onions are growing and before harvesting.

See NIWA for more information.

Onions are an annual crop, meaning you will get one crop over a 12 month period.

When planning to plant onions, you will need to consider your geographic location and the types of onions suited to this location. Different varieties of onions will grow better in the North and South Island due to the day lengths. For advice on what types of onions suit your whenua, talk to Onions NZ.

Onions NZ

Onions growing guide

There are three phases of onion growth:

1. vegetative phase, when the leaves form,
2. bulb formation, and
3. blooming, otherwise known as bolting.

You may need machinery to prepare your whenua for planting onion seeds.

Onion seeds germinate when the temperature and moisture conditions on your whenua are favourable. In Aotearoa, this is usually during June - August.

Onions will grow for 7 - 9 months before they're ready to be harvested (November - early April). When the necks of onions become soft and the tops fall over, harvesting can begin.

Harvesting onions can be done by hand or using machinery. This is dependent on how mature or vulnerable the bulbs are.

After harvesting the onions from the ground, they're left out to dry on top of whenua. This helps them develop a protective skin and minimise any rot forming. After drying out for around 5 days in the sun, they're collected and transported to a packhouse.

After harvesting your onions, the storage of your crop is very important. This ensures your crop can get to international and domestic markets in the best possible quality.

Packhouses will store your crop for at least 10 days. This helps to finish the curing process and maintain the quality of the crop. A cool store will hold your onions for longer periods to be sold later in the season.

Onions can be affected by fungal diseases and pests like aphids and thrips. You will need consider using pest management methods, such as:

• counting the number and species of pests weekly
• monitoring crops to assess plant health
• making the environment attractive to insects that can eat pests
• targeted use of fungicides and pesticides.

Learn more about pest management.

The main environmental risks of growing onions relate to poor management of fertiliser application.

Nitrate leaching

If you apply too much fertiliser, at the wrong time, it can pollute our groundwater and connecting waterways if it travels beyond the plant root zone. This is called nitrate leaching. Leaching is more likely to happen when there are long wet periods, especially in autumn and winter.

To manage the risk of nitrate leaching, you can:

• stay informed about weather patterns to avoid applying fertiliser during long wet periods
• do soil testing to help you understand the nutrient levels in your whenua. This will help you determine how much fertiliser to apply without over applying fertiliser.
• plant a deep-rooted crop immediately after harvesting your onions. This will absorb excess nutrients in the soil
• provide routes for runoff of rainwater to mitigate the impact on waterways.

Learn more about good environmental practices

Degraded soil structure and fertility

The more you use the soil for growing crops, the soil structure and fertility degrades over time. This impacts your whenua's ability to support growing crops.

To help your whenua support further crops of onions, you will need to consider:

• testing your soil to understand its fertility and soil structure.
• adding nutrients to help the soil recover.
• planting a deep-rooted crop after harvesting your onions to absorb excess nutrients.

Onions NZ

Onions New Zealand represents 85 growers and 18 exporters. Export members of this group pay a voluntary levy to fund collective research into market access.

Learn more about Onions NZ

Facts and figures about onions

Export market

New Zealand's onion export market was worth about $150 million in 2020, with Europe making up 40% of this market.

Scale

Onions can return a profit from a small or large-scale enterprise. Turning a profit from growing onions depends on several factors, like:

• your location - access to the market, or infrastructure, or to a packhouse
• your production practices - modern machinery and equipment or smaller scale efficiencies
• the market demand and access to the market
• your operational efficiencies - larger farms may benefit from economies of scale.

Equipment and infrastructure

There are various tools and equipment needed for growing and harvesting onions. These include:

• tractors and other field machinery, for example, harvesters
• ploughs
• harrows
• seeders
• cultivators, and
• irrigation systems.

It's estimated that you'll need to grow at least 5 hectares of onions to offset the costs of investing in machinery and equipment. Contractors could be used to provide some of these services if you are farming on a smaller scale.

After harvesting your crop, you'll need well-ventilated storage sheds to maintain the quality of your onions. You'll need to sort, grade, clean, and pack your onions into bags or crates, ready for the market. If you're located near a packhouse and can partner with them, they'll help you with this.

Jobs and people

Your people and labour requirements are seasonal, based on key milestones, like planting. You'll need a mixture of unskilled labour, as well as specialists. The specialists will help you with:

• managing the crop cycle,
• pest management techniques,
• harvesting and,
• post-harvest management.

The peak demand for labour and specialists by onion farmers is during planting and harvesting times.

Estimate of people needed for onion growing milestones

Onions NZ

Tupu.nz

Case study - Pukekohe Onion farm

Here is an example of an onion farm in Pukekohe, let's imagine it had 100 hectares of onions grown last year.

It yielded 4050 tonnes of onions, bringing in a revenue of $2,200,000.

It had $1,700,000 in expenses, and the farm made a profit of $540,000.

It took 6-8 months for the onions to be ready for harvest and then sold (time to commercial yield).

Operational costs

The estimated operational costs to grow onions are around $17,000 per hectare per year. This depends on factors, like:

• scale of the operation
• level of mechanisation
• specific farming practices
• regional and locational factors
• market conditions.

Labour costs can be significant, especially when you're first setting up your farm. Some other examples of costs that you'll need to consider are:

• seeds or sets
• fertilisers
• pesticides and herbicides
• agrochemicals for onion cultivation
• skilled and unskilled labour
• permits, licenses, or certifications
• compliance with regulations and food safety standards.

Costs

There are some costs you will need to consider, and these will change with the amount produced. Here are some examples:

Yield (and time to profit)

It typically takes several years to establish a sustainable and profitable operation.

Maximising the amount of good quality onions grown will increase the profits you earn. Factors that can contribute to higher onion yields include:

• crop management
• variety selection
• planting density
• nutrient management
• weed control
• harvesting at the right time.

Revenue

Returns from onion farming are influenced by a variety of factors, including:

• market conditions
• yield
• quality
• production costs
• pricing strategies
• events beyond your control, for example weather conditions or market fluctuations.

Things we can do to create better returns include:

• efficient practices to maximise yield and production.
• market demand and pricing
• quality and grading
• Cost management
• Storage and post-harvest handling
• Value-added opportunities

To help you make informed decisions and maximise returns, it's important for you to:

• stay informed about market trends through research.
• maintain good relationships with buyers.
• regularly assess your farm's production and financial performance through tracking costs.

Operating profit

To estimate your operating profit, you must look at the money generated from selling your onions, minus your production costs. Some factors may affect your revenue and influence your farm's operating profit. These include:

• farm size or the size of your onion crop area
• yield - the quantity of onions sold
• market conditions and fluctuations
• production costs and efficient farming practices
• pricing strategies
• weather conditions.

You will need to consider your production costs, which can include:

• labour
• seed costs
• fertilisers
• irrigation
• pest and disease management
• machinery maintenance
• storage
• packaging
• marketing costs.

These costs can be affected by having efficient farming practices and effective cost management.

Each farm will have factors specific to them and different market dynamics. Keeping accurate records of your production and financial records can help you see where improvements could be made and increase your operating profit.

Aotearoa exports onions to over 45 countries. The authorities can provide information on what's needed to export onions, including:

• procedures
• documentation
• fees or licences
• packaging standards
• biosecurity requirements.

To export onions, you need to follow legislative requirements, including:

• paying levies to Onions New Zealand and Horticulture New Zealand on the sale of your onions
• meeting export requirements, like documentation and packaging standards
• ensuring food is grown so it can be sold under the Food Act 2014
• meeting regulations around risks to freshwater.

Further information about exporting onions

You would pay $0.14 per $100 of sales to Horticulture New Zealand, which goes towards industry-wide maintenance and development activities.

You would pay $2.50 per ton sold to Onions New Zealand and the last levy year is 2025. If the amount or ending year changes, you will be notified. This money is for crop-specific activities, like research and development or domestic promotion.

Learn more about levies

You must comply with National Programme 1 requirements under the Food Act 2014. This includes:

• following safe food practices, like checking for pests and using clean water
• registering your business with either your local council or MPI
• getting your business verified.

Learn more about National Programme 1.

You will need a freshwater farm plan, either now or by 2025 if your whenua will have:

• 20 hectares or more of arable and/or pastoral use, or
• 5 hectares or more of horticultural use, or
• 20 hectares or more of combined uses.

These plans identify actions to manage and mitigate risks of on-farm activity to freshwater. They must be certified and audited, then recertified every 5 years.

Learn more about freshwater farm plans.

Some additional certifications and registrations may make your onions more appealing to buyers.

You can choose to get certified with NZGAP for a yearly fee. Some retailers and wholesalers only take crops from an NZGAP-certified supply channel.

If you are planning to export onions, you can register with Asure Quality to be listed as being onion smut-free. Onion smut is a destructive fungal disease.

Learn more about Asure Quality.