Practice Guide: Foliar Applications

PART OF A SERIES OF PRACTICE GUIDES TO USE IN YOUR REGENERATIVE CROPPING TOOLSET | LAST UPDATED: FEBRUARY 2025

Overview

Foliar applications involve spraying dissolved nutrients and/or beneficial ingredients such as biostimulants¹ and microbial inoculants onto crop foliage during the growing season.

Using foliar applications to supply targeted nutrients and biostimulants to plants has become a common tool among farmers focusing on soil health. Foliar applications in cropping systems can be a useful method of supplying small quantities of targeted nutrients, correcting deficiencies and supporting crops under challenging soil conditions. Foliars excel when crops require quick adjustments to micronutrients or minor nutrient boosts during critical growth stages. Foliar applications can also support crop growth and resilience to pests, pathogens and weather.

This guide is designed to help you decide if foliar applications could be a useful part of your crop nutrition and approach to inputs and to help you get started. Throughout the guide, we share the experience and tips from two farming families from cropping regions in New South Wales and South Australia who use foliar applications. The guide covers some common foliar ingredients, application rates, tank mixing and tips for achieving good leaf coverage.

Multispecies cropping involves the use of multiple crop species from diverse plant families at the same time. The practice is often used to bring diversity into farming systems, transition ‘problem’ paddocks and build farm resilience.

This guide is an introduction to multispecies cropping. It covers the benefits of this practice, decisions on what seeds to use, application methods, complementary practices and what to look for to know if your multispecies crops are working. Like all practices, it must be considered in the unique context of each farm. For this reason, the guide shares three different examples of how farmers have integrated multispecies into their diverse operations in Victoria, Queensland and Western Australia.

Before trying a new practice, it is important to consider your unique context and goals. What are you trying to achieve? Soil and landscape ecosystems are complex, and no two farming systems are the same – what worked for one farmer may not work for you. So consider starting small, monitoring the results and allowing some room for trial and error. There is no silver bullet when it comes to addressing soil health, so think about which strategies or combinations of other practices may be suitable to support what you’re doing, and check out our other guides here: (Add link to main PG portal)

Before trying a new practice, it is important to consider your unique context and goals. What are you trying to achieve? Soil and landscape ecosystems are complex, and no two farming systems are the same – what worked for one farmer may not work for you. So consider starting small, monitoring the results and allowing some room for trial and error. There is no silver bullet when it comes to addressing soil health, so think about which strategies or combinations of other practices may be suitable to support what you’re doing.

Important: This Guide is designed to provide general information only. It is not tailored to the context of any individual farm, person or business, and does not constitute advice. Before using the information, you should carefully evaluate its accuracy, currency, completeness and relevance for your purposes, and consider seeking advice from appropriate professionals who have taken into account your individual circumstances and objectives. As a nonprofit dedicated to supporting farmers, we work hard to ensure our information is useful and accurate. However, Soils for Life accepts no liability arising from any use or release of information in, or referred to in or linked to this guide, or any error, inaccuracy or omission.

Other guides to check out

What are foliar applications?

Foliar applications, or ‘foliars’, involve applying ingredients dissolved in a solution directly to plant leaves using spray equipment. Soluble fertilisers are often the focus of foliar applications, but spray passes can also include other plant growth-promoting ingredients, such as biostimulants like seaweed extracts and beneficial microbe inoculants.

Leaf uptake: Foliar-applied nutrients are known to be taken up through several entry points in plant tissue, including the cuticle, stomata, trichomes and veins² (see Diagram 1). Foliar absorption of nutrients has been studied for over a century, but there is still a lot that is not well understood about exactly how it works.³ The uptake of nutrients into the leaf for movement around the plant is likely to vary depending on the crop species, growth stage and the specific nutrient form and spray mix. Keep your eyes and ears open for new research and insights.

Diagram 1. A cross section of a leaf, showing some of the known points of absorption for nutrients via foliar application. Source: Soils for Life.

Foliars provide complementary, targeted plant support: Rather than supplying the bulk of a crop’s nutrition, foliar-applied fertilisers can be used to provide small, targeted quantities of micronutrients to correct deficiencies and prime plant function and/or well-timed top-ups of other nutrients to meet periods of crop growth. Foliars can be used to hone and maintain optimum plant health throughout the growing season or during periods of stress. One common reason for using foliars is to support the transition to a lower-input farming system with reduced/optimised use of synthetic granular fertiliser. Transitioning towards timely nutrition applications in sync with crop requirements can also help minimise nutrient losses.

Foliars mostly supplement, rather than replace, crop nutrients accessed from plant roots and soil. It is unlikely that the total nutrient needs of a crop can be met through foliars alone; soil nutrient cycling is still essential. Healthy plants help build healthy soil and vice versa, and so foliars can complement soil fertility and play a part in building resilience in the whole plant-soil health system. Like any tool, foliars have their practical limitations and nutrient losses to the soil and air are still possible. Keep in mind that there is still much to learn about foliar uptake, nutrient interactions on the plant leaf surface and nutrient movement within the plant.

Farmers who are using foliars

This guide includes examples from two Australian family run farms throughout, showing their approach to foliars in their farming systems in South Australia and New South Wales.

Jordan and Karen Hoskinson run Dirragarra Ag in Kikoria, New South Wales, where they grow mixed crops, run merino sheep and produce pasture-raised eggs through their latest venture, ‘Paddock Peckers’.

Like many others, it was a drought that had Jordan sitting on his verandah, ‘watching the dust blow around’ his multi-generation property, that sparked an ‘aha’ moment. Jordan took a Holistic Management course and his approach to farming started to shift gears. He credits Karen for laying the foundations for what has become their purpose- and profitability-driven approach to farming and soil health.

The Hoskinsons are relatively early on in their journey of optimising their cropping inputs. Jordan says fertilising is ‘a bit like greasing a bearing. You give it a heap, you’re gonna cause problems.’ Instead, they apply ‘just a little bit here and there as it needs it’. Three years into utilising foliars, the Hoskinsons are a great example of how to get started and use monitoring tools to track changes and make input decisions.

Location: Wiradjuri Country, Kikoira, New South Wales

Regional Climate: Hot dry summer, cold winter/temperate sub-humid

Average Annual Rainfall: 450 mm

Property Size: 800 ha (around 240 ha cropping)

Elevation: 240 m

Social Structure: Family farm

Enterprise Type: Broadacre cropping, merino sheep and pasture-raised poultry

Foliar applications: Micronutrients, some macronutrients and biostimulants.

Soils: Predominantly calcarosols and kandosols. Varies from heavy clays, loams and self-mulching clays, as well as some red granite country.

Tom and Cassi Robinson run Robinson Farms near Hoyleton, South Australia. Tom is a sixth generation farmer, and his parents, Ashley and Kaylene, were some of the first farmers in South Australia to adopt zero-till in the 1990s. Building on this, Tom and Cassi have continued to hone the zero-till system with full stubble retention using disc planting and a strip header. They also moved the farm out of continuous cropping and introduced livestock to complement their cropping system and build soil health.

They grow a large variety of crops depending on the seasonal forecasts, often including wheat, lentils, barley, canola, field peas and faba beans. Around a decade ago, they started to see the cracks in their high input, high cost cropping system. The Robinsons have a strong focus on supporting optimum plant function for growth and resilience. Foliar applications and extensive soil and plant monitoring are key to their approach.

**Location: Kaurna and Ngadjuri Country, Hoyleton, South Australia**

Regional Climate: Warm summer, cold winter/mediterranean

Average Annual Rainfall: 325-425 mm

Property Size: 1,214 ha

Elevation: 190 m

Social Structure: Family farm

Enterprise Type: Mixed broadacre cropping (growing a variety of crops including wheat, lentils, barley, canola and others). Cattle and mixed species winter or summer annuals for grazing or hay, as well as a Highland cattle stud

Foliar applications: Micronutrients, some macronutrients and biostimulants.

Soils: Mostly calcarosols and chromosols. Red brown earth loam and loam clays, with some heavier clay up under the hills.

What are the benefits?

A targeted method for applying timely crop nutrition and other beneficial inputs that support optimised plant and soil health and resilience.

Reduce soil-applied nutrients: Reducing nutrient excess (and costs) is important in driving transitions towards effective and sustainable crop nutrition programs. Foliar applications have the potential to be a part of meeting but not exceeding crop nutrition needs, given that applying excess soil-applied fertiliser can impact soil health long term.⁴ Well-designed, targeted applications have the potential to boost product quality, maintain growth and can be a way to support plant health when soil constraints or adverse growing conditions arise.

Address micronutrient deficiencies and provide macronutrient ‘top ups’: Foliars can be beneficial for crop metabolism, quality and yield.⁵ Foliars are particularly effective for rapidly addressing micronutrient deficiencies, often providing more reliable supply than granular fertilisers.⁶ Effectively applying foliar sprays with micronutrients like boron, copper, iron, manganese, molybdenum and zinc can quickly help alleviate deficiency symptoms, often more efficiently than soil applications. If nutrient deficiencies are too severe or left too long, this can also affect the ability of plants to take up foliar-applied nutrients.⁷

For macronutrients, foliars are more about having the flexibility to provide a ‘tactical top up’;⁸ soil remains the most effective way to provide the bulk of the plants macronutrient needs.⁹ There are limits to the amount of macronutrients that can be applied through foliar methods due to the risk of leaf burn and the number of passes with the boom spray that are practical in one crop cycle.¹⁰

Plant health support in stressed growing conditions: When soil or environmental factors suppress nutrient availability in the soil (e.g. in low moisture, high salinity or pH constraints), foliar treatments can bypass the soil and provide an immediate nutrient supply to the crop for growth and grain fill.¹¹ Under drought and salinity stress, foliar-applied nutrients have been shown to increase yield by 15–19% and crop quality traits by 9–29%.¹² Keep in mind that if plants experience long-term adverse growing conditions, even foliars won’t be able to help because the stress will eventually begin to shut down most nutrient uptake pathways, including the leaves.

Improve product quality: Often called biofortification, foliar applications of micronutrients can boost nutrient density in grain, although the effectiveness of nutrient uptake likely depends on the plant having adequate nutrition from the soil.¹³ Foliar nitrogen, in particular, is gaining momentum as a efficient way to support grain protein while supporting crop growth.¹⁴

Opportunity to apply other beneficial products: In addition to spraying dissolved crop nutrition, foliar applications provide an opportunity to apply other products, such as biostimulants, to the crop. Examples of biostimulants include kelp/seaweed extracts, worm compost products, fulvic and humic acids, protein hydrolysates and microbial inoculations.¹⁵ Biostimulants have been found to increase crop yield and quality and to further support plants in stressful conditions such as drought.¹⁶ The crop growth-promoting effects of biostimulants are thought to be from changes in plant growth regulators and hormones, supporting nutrient uptake and the improved ability to ward off plant pathogens on the leaf surface.¹⁷

The Hoskinsons are farming to build soil health and product quality, with profitability front of mind. Using foliars to overcome soil limitations and to back off on some of the soil-applied fertilisers gives them more control and ability to adapt within the season.

‘There’s just some things on those soil tests that are not economical to adjust in the soil. But we can foliar feed the plants as they need those nutrients.’ Jordan Hoskinson

Jordan and Karen’s region experienced dry conditions in 2023, and there wasn’t enough rainfall to see the grain through to harvest. They ended up grazing the crop instead. In seasons such as these, their measured approach to soil- and foliar-applied fertiliser wins out, limiting expenses. Jordan feels it is more cost-effective to ‘not overload it all at the start with all your fertiliser’. So while he lost the grain, he ‘got a bit of grazing without too much cost’. With the recent rise in fertiliser costs, he sees planting with high urea rates as ‘throwing $100 bills in the paddock’.

By increasing their monitoring through the season with soil and plant testing, the Hoskinsons have gained insight into crop health. Jordan recently had a wheat paddock that he assumed was yellowed due to nitrogen deficiency. Testing showed it lacked boron, copper and magnesium. They quickly addressed the deficiencies with a successful foliar spray.

The Robinsons have been fine-tuning their fertilising programs for some time now, with foliars playing a central role. They focus on meeting the crop’s needs throughout the season, and now use only about 20–30% of their past granular fertiliser rates, which comes with some big cost savings. They use micronutrient foliar applications to support plant function to get the most out of their limited daylight hours in a winter growing season. The Robinsons compare subpar plant health to having ‘dirty solar panels’ and see it as a missed opportunity to fuel the relationship between plant and soil health. Soil moisture in their region is regularly limiting to nutrient uptake, so they use foliars to ‘shortcut the system’ and help plants when soil nutrient availability and mineralisation are affected. Foliar applications are part of the ’jigsaw puzzle’ of their crop nutrition that helps ‘make it all work’.

‘…healthy soils, healthy plants and then healthy animals and …healthy grains.’ Tom Robinson

How to apply foliars

Applying foliar crop nutrition and biostimulants is similar to how you might go about other crop sprays, with a few additional considerations. Getting an effective crop response from foliars depends on:

Starting with crop monitoring
Ingredients and rates
Mixing the ingredients
Equipment and applications

It is not uncommon for farmers to report varied results with foliars, and it may take some experimentation and perseverance to optimise mixes, application methods and uptake. You know your farm and your equipment best, so keep your own context front of mind. Consider experimenting on a small scale and assessing the results first.

Image 3. Spray equipment that is used for foliar applications at Robinsons Farm. Source: Tom Robinson.

Start with crop monitoring

Pairing visual observations with soil and plant testing is key to understanding the nutrient needs throughout and between seasons and making fertiliser decisions, including decisions about foliars. Nutrients can become immobilised or ‘stuck’ in soil, and plant testing gives you a better picture of what the crop can access.¹⁸ Jordan sees soil and plant monitoring as going ‘hand in hand. You can’t do one and not the other.’

Visual symptoms: Nutrient deficiencies or excesses in crops can look like leaf discolouration, reduced height, tillering and overall growth suppression.¹⁹ Look for patterns in nutrient symptoms over an area and not on individual plants. Not all crop nutrition deficiencies have obvious visual cues and yield may already be lost by the time it can be seen in the crop, so monitoring via soil and plant testing is also helpful.²⁰

Soil testing: Soil lab testing can give you useful information about the total and available nutrients in your soil, as well as other soil properties like organic matter %, pH and cation exchange capacity (CEC).²¹ Pairing soil lab testing with in-paddock soil health monitoring gives a holistic picture of your soil’s structural and biological health as well as the available nutrients. Check out our soil health assessment guide for instructions on how to conduct easy in-field monitoring yourself.

Plant testing: You can get plant testing done by a lab from plant sap or dried plant tissue that you provide. Plant testing is especially important for identifying micronutrient deficiencies.²² Dried plant samples show the total nutrients stored in the plant tissues and sap testing can provide a real-time snapshot of nutrient uptake at the time of sampling.²³

Both Jordan and Tom have used sap testing to understand nutrient availability to the crop within a growing season, identify deficiencies and inform decisions about foliar applications. Sap testing has been more commonly used in horticulture, but there is a growing group of broadacre croppers using sap testing as an in-season monitoring tool.²⁴

Tips and tricks

Keep in mind that there are no current universal reference ranges or standardised lab methods for sap analysis for all crops.²⁵
Talk to the lab you are using about their reference range for specific crop/varieties. Care should be taken to follow similar sampling methods over time to get reliable results from plant and soil tests.
Sap sampling results are particularly sensitive to environmental changes, so ensure you’re sampling at the same time of day as well as from the same variety, growth stage, plant part and paddock history.

Find out more: For dried plant tissue analysis, samples sent to the lab should contain at least 20 to 30 leaves for large-leaved crops and 40 to 50 leaves for small-leaved crops. Sap samples (petiole or leaf stem samples) should contain between 100 and 150 petioles. Find out more about taking reliable plant samples in FertCare’s Plant Sampling for Agriculture – A Guide.

‘Do some testing, work out what’s going on, and then…have a strategic plan around what you’re going to put out. There’s no point putting out zinc or copper if you don’t need it.’ Tom Robinson

A lot of monitoring goes on at Robinsons Farm. Tom and Cassi collect plant samples for testing at critical growth stages to give an indication of ‘how the plant is responding to the season and the soil in that paddock’. In wheat crops, this usually happens at tillering, stem elongation and flag leaf. In legume crops, they will often test at pre-flowering, flowering and pod fill. The Robinsons aim for a quick turnaround between taking samples, getting the results and spraying out a foliar. They have found sap testing to be a handy tool to unpack the available nutrients in the plant at any given time. They test new and old leaves to see how nutrients are moving around the plant as the crop grows and also do soil and deep nitrogen testing to get a full picture of nutrient availability throughout the seasons.

Tom and Cassi have also started using sap testing as a way to measure the effectiveness of new blends and products by doing sap tests two to three weeks post application. One of Tom’s main pieces of advice for other farmers is the common catchphrase, ‘Test, don’t guess’.

Ingredients and rates

Ingredients: The ingredients in a foliar spray will depend on the outcomes you’re trying to achieve, which should be informed by monitoring of plants and soils (see above). Consider the nutrient you are targeting and what form of that nutrient is available, as well as its ability to be taken up by the leaf. Urea, for example, is thought to be an effective form of inorganic nitrogen for leaf absorption.²⁶

Appendix 1 lists some of the common macro- and micronutrients, their roles in soil and plant health, forms they can come in and other considerations for their use. See our article on Working with Bioamendments for similar information on biostimulants and microbial inoculants.

Appendices: Some foliar nutrient products and considerations

Be aware of insoluble impurities, coatings and granulation agents in some fertiliser products, even if the main ingredient is soluble.²⁷ Impurities can block nozzles and filters or cause crop damage. Biuret is an impurity commonly found in urea. Any urea product dissolved for use in a foliar mix should have a low biuret content of around 0.4% or less to avoid crop damage.²⁸ Read the label and consider talking to your supplier about what impurities might be present in products.

Compatibility: Antagonisms can occur between products in a tank mix, causing the original ingredients or by-products to ‘drop out’ or ‘salt out’ of the solution (precipitate). This can cause blockages and issues with hoses, nozzles, and equipment. As a general rule of thumb, ‘salting out’ is more likely to occur in low volume sprays and cold water. Note that sulfates do not have much compatibility with other fertilisers in solution.

Find out more: There’s useful information about some product incompatibility in this Incitec AgriTopic and this SoilWealth fact sheet.

Rates: Foliar mixes are highly specific to a crop at a certain point in time and ‘recipes’ and rates aren’t often possible or useful. As a general rule of thumb, in cropping:²⁹

Micronutrients are applied as 1% solutions (1 kg/100 L) in low-volume sprays (<100 L/ha)
Macronutrients are generally applied at higher concentrations, often in the range of 5–10% of water volume in field crops (5–10 kg/100 L).
Spray volumes of 100 L/ha or lower are often used for applications in grain crops, but use your equipment as you see fit to achieve good coverage.

It’s important to be very careful to avoid foliar burns caused by nutrient solutions at too high of a concentration.³⁰ Most practitioners recommend test spraying on a small section of crop and observing for several days before a broadacre application to check for any phytotoxicity (leaf burn) if you are unsure.

For biological inputs that can be applied as foliars, these are some ‘rule of thumb’ rates for, as recommended by plant and soil health expert, Joel Williams:³¹

Molasses/sugars: 5 L/ha
Humic acids: 3–5 L/ha (double check product label rates)
Fulvic acids: 1–2 L/ha (double check product label rates)
Amino acids: label rates
Protein hydrolysates: 2–5 L/ha
Seaweed/kelp extract: 2–5L/ha
Plant extracts: 10+ L/ha
Compost extracts: 10+ L/ha

The Robinsons typically apply between two to four applications of dissolved urea (at a rate of 8–10 kg N/ha each) per season. Each pass includes fulvic acid, molasses, biostimulants such as seaweed or compost extract and a tailored mix of micronutrients, depending on the sap test results.

The Hoskinsons have developed a foliar program that tends to include nitrogen buffered with humic acid, calcium, biostimulants and micronutrients like boron and copper. They usually apply a foliar around three times each growing season, ideally at late tillering, early elongation and flag leaf. They also plant with reduced soil-applied fertiliser up front and then follow up with one or two applications of urea during the season.

Tips and Tricks

For farmers new to tweaking their usual fertilising routine, Tom sometimes suggests using about 20% of your standard fertiliser budget and redirecting this investment into diversifying your nutrition program a bit, such as including foliar micronutrients and biostimulants.
Start small with a new practice and see how it might work for you rather than going ‘all in’. By measuring your success, you can keep adjusting and experimenting each season.

Spray additives: Spray additives can help droplets stick to leaves (see Table 3 for some types and examples to consider). The longer the droplets stick and spread on the leaf surface, the more time there is for uptake and the better your chances are of a successful foliar application.³² Keep in mind that different crops have different leaf surfaces and ‘wettability’.³³ A foliar phosphorus application has been recorded bouncing off wheat leaves in the absence of an adjuvant.³⁴ Depending on leaf waxiness and the roughness of the leaf surface, some crops are harder to wet than others, so a surfactant adjuvant can help spray droplets stick to leaves. Additives are also important to consider if you’re applying mixes with living microbes that are sensitive to droplets drying out too quickly.³⁵ If you are using pre-mixed foliar products, check to see what adjuvants are already included.

Some types of spray additives have been found to have potential eco-toxicity effects, particularly petrol-based additives that aren’t biodegradable.³⁶ You may want to keep this in mind when selecting which products to use.

Table 3. Examples of the types of adjuvants that might be considered and why they are added to spray mixes. ³⁷

Environmental impacts of products: While ingredients in foliar applications are often applied in targeted, small quantities, many products are still synthetically sourced or mined. Products are also often shipped long distances before they find their way to a tank mix and a paddock. You may like to ask your supplier how they source their products and if there are options available that are more local or naturally sourced.

Mixing the ingredients

Test your water: The first step in setting up a foliar application for success is to use a high quality water source for mixing. Consider testing your water to ensure it is suitable for use in foliar sprays. You can test for conductivity (max 50 mS/cm or 500 uS/cm), pH max 6 pH), hardness (max 250 ppm CaCO3 equivalent) and suspended solids.⁴⁰ NSW DPI has produced a handy factsheet on water testing (see here).

Jar test: Both Jordan and Tom suggest jar testing as the first step in checking the compatibility of a tank mix before applying it in the paddock to avoid wasting time and product.⁴¹ Leave jar tests to sit for at least 30 minutes. Compatible mixes should have a consistent, stable appearance without any layers or sediments having formed.

Chelation: Some farmers choose to add ingredients to their foliar mixes that can ‘chelate’ nutrients, which can lead to improved compatibility in tank mixes, and potentially reduce the risk of leaf burn and improve nutrient uptake.⁴² Chelation occurs when nutrients are bound with another compound, making them more stable and less reactive. Fulvic acid and citric acid are common products added to chelate nutrients in foliar sprays. Synthetic chelates such as EDTA are often used but how well they biodegrade is relatively unknown.⁴³ Another emerging option is amino acid chelates such as glycine, which is thought to be particularly effective as its small size means it can be taken up into the leaf more effectively.⁴⁴

The Hoskinsons use pre-mixed products. Although it costs a little more than buying individual ingredients and mixing these themselves, the savings in time and confidence in compatibility is are worth it for them at this stage.

The Robinsons tend to buy raw sulfate forms of the micronutrients they want to apply as foliars. They often chelate these themselves on-farm with citric and fulvic acid.

Mixing order: Following a well-planned tank mixing order can help prevent unnecessary reactions between products that risk wasted product and time. Always read the product labels, take note of product pH and follow any specific instructions first. The following mixing order is recommended by NutriTech Solutions’ Nutrition Farming Course.⁴³ The Robinsons tend to use an order such as this as a general rule of thumb; however, they always use jar tests to check compatibility and make adjustments depending on the products being used:

Clean water
Pesticides
Biostimulants
Nutrients (generally added in order from least to most soluble)
Adjuvants (i.e. surfactants)
Biology (needs relatively diluted solutions; if higher concentrations of nutrients are used, then biology might not be able to be applied)

It’s ideal to use a pH and electrical conductivity (EC) meter to test the solution once mixing is complete. Ideally, a foliar application should be slightly acidic for leaf penetration. Aim to have the solution pH between 5.0 and 6.5 and 1.5–3 mS/cm EC.⁴⁵

The Robinsons mix most of their foliar products from scratch and have been fine-tuning the process and equipment for a while now. Given the extent of their foliar program, they use shuttles to mix individual products into solutions (or combinations they know are highly compatible), adding fulvic or citric acid chelating agents first, followed by micronutrients. They then combine these pre-mixed solutions and other ingredients in the spray tank, generally by mixing micronutrients, followed by urea and then biostimulants like fish hydrolysates and molasses. They tend to add anything with live microbes last.

The Hoskinsons tend to dissolve a humic and urea blend first, followed by a liquid calcium product and then micronutrients. Jordan adds fish hydrolysate at the end, after noticing that it made the mix foam up if added too early.

Image 4. Due to the scale of foliar operations at Robinson Farms, micronutrients are often mixed in individual shuttles and then drawn from each to combine in the spray tank. Source: Tom Robinson.

Equipment and application

Like anything mixed together in a tank and applied with a boom spray, there is a bit to consider. Solubility and knowing how your equipment is set up and calibrated for good coverage is key.

Applying foliars requires similar equipment to other sprays and similar considerations for application, with a few additional considerations relating to:

Avoiding chemical residues
Nozzles and droplet size
Timing of applications
Spray additives

The Robinsons use a standard broadacre boom spray to apply foliars and have just the one machine to do all of the farm’s spraying jobs. They are careful to filter down foliar mixes because their boom spray doesn’t handle anything ‘chunky’. They’ve converted 1000 L shuttles to circulate water for mixing products by sucking solution out from a hose at the bottom of the shuttle and then pumping back in closer to the top with a standard firefighting pump. Tom has also started using a 2-inch spa pump to warm a half to three-quarter full shuttle of water overnight to make it easier to use products like urea, which struggle to dissolve in cold temperatures.

The Hoskinsons use a jet stream boom spray that Jordan modified himself to apply foliars with good coverage. They are a great example that you don’t need million-dollar equipment to give foliars a go.

Avoiding chemical residues: Especially if you’re using a variety of products or the same tank for chemical and foliar fertiliser applications, it is important to wash equipment between uses. Residues might affect the effectiveness of the following tank mix.

Nozzles and droplet size: Nozzles play a crucial role in the effectiveness of a foliar application and need to be cleaned, calibrated regularly and replaced when necessary. The cost of nozzles can be relatively small compared to the value and potential benefits to the crop from the products passing through them.

Consider the crop type and the droplet size needed. Droplets from foliar nutrient applications are generally a bit coarser than those used for insecticides and fungicides. Ideally, the droplets should circulate in the crop canopy and get coverage on the underside of the leaf for optimal absorption. Broad-leaf crops with horizontal leaves are a different target from cereals, and finer droplets can often be moved effectively around the crop with air turbulence. For tall, thin targets, larger spray droplets penetrate better into the canopy than a fine mist. For nutrient foliars, larger droplets are often used to get good leaf coverage and to slow down evaporation of the droplet so that there’s enough time for adsorption into the leaf.

Find out more: See the GRDC Back Pocket Guide for more information on nozzle selection.

Image 5 and 6. For mixing, the Robinsons keep water agitated by circulating it from the top to the bottom of shuttles with a standard firefighting pump. They have also converted spa-pool pumps for heating water to improve the solubility of some ingredients, such as urea. Source: Tom Robinson.

Timing of applications: Broadly, the timing of foliar applications will coincide with certain growth stages or when deficiencies crop up.

Foliars are believed to be most effective in the early morning (ideally) or late afternoon when humidity is highest and temperatures are lower.⁴⁶ You should also check Delta T⁴⁷ and the weather for upcoming rain before heading out with the boom spray to minimise spray drift and wash. Both Tom and Jordan say that they ideally apply foliars when the temperature is below 24°C.

For the Robinsons, timing foliars with ‘critical points of influence’ is key. In a grain crop, this is often at tillering, stem elongation and pre-flag leaf development. This is combined with reduced rates of soil-applied fertiliser at planting (generally some nitrogen, phosphorus and sulphur, as their soils have naturally high potassium), followed up with one or two small foliar applications of nitrogen during the growing season. Tom aims to give the crop a boost during growth and development stages for optimum plant function, root growth and photosynthesis.

Finances

There are lots of variables when it comes to the costs of foliar applications and how they fit into an overall crop nutrition program.

Below are some price examples of individual products and rates used by the Robinsons and Hoskinsons to give you an idea of the approximate costs.

Note that this isn’t a tank mix example, and is showing individual product costs as of 2024 only. The rates used are just examples from the Robinsons’ and Hoskinsons’ past applications and their farms’ contexts.

Table 4. An indication of some per hectare costs from Tom and Jordan that you might expect of foliar products and application costs.

The Robinsons do an average of three to four passes with the boom spray per crop per season. Considering the efficiencies of combining their insecticide and fungicide sprays (when required) with some of their foliar mixes, it is not many more passes than they have done in the past, so additional fuel and equipment costs are negligible.

Indicators of success

Many farmers say that soil and plant health monitoring is the backbone of input decisions on-farm, especially when it comes to applying foliars. Don’t forget to keep an eye on changes in soil structure and microbial life too, both are vital drivers of soil fertility.

The Hoskinsons pay close attention to the presence of rhizosheaths on crop roots along with the results from plant and tissue tests, as they feel these provide important in-crop indicators. Since adopting a soil health driven approach, the Hoskinsons have noticed improvements in their soil lab test results, with less acidity across the farm.

The Robinsons have noticed some ‘really tremendous’ grain test weights since honing in on nutrition and crop quality with foliars.

Track soil and plant health over time: The key to tracking your success when trying out foliar applications is to keep a consistent record of plant and soil testing, so you can spot patterns and changes in the whole soil and plant system.

In one paddock, Tom realised that he had been potentially propping up an underlying soil zinc deficiency with foliars after noticing a consistent lack of zinc in plant tissue results over several seasons. This coming season, he plans to add some zinc to the soil-applied fertiliser to tackle the issue but will still rely on foliar applications to boost zinc levels if necessary.

Test strips: Jordan recommends that others use a strip test on their paddock to visually track the success of foliars. He suggests excluding a 20–30 m wide section of a paddock from the foliar applications. Establishing test strips can help you see how your approach to nutrition is impacting plant growth. By leaving a strip in the paddock unsprayed with foliar applications over the growing season, you might be able to detect subtle differences in the crop.

Quality and profitability: Some farmers are starting to use foliars to improve grain quality and to open up opportunities in potential markets. Despite being early on in the journey of tweaking their crop nutrition program, Jordan and Karen say they have seen ‘huge changes’. Their focus on plant and soil health has resulted in ‘some of the nicest grain I’ve seen’ with improved protein, storage and reduced screenings. The improvements in quality and more control over input costs are ‘indicators of success’ that motivate them to keep going down this path. Jordan and Karen are also exploring alternative markets for their grain, aiming to gain more control over pricing and hopefully increase their profit margins even further.

Image 8. Visual assessment of foliars at the Hoskinsons farm, Dirragarra Ag. You can see the left side of the paddock where a foliar was sprayed has subtle visual differences with the right side of the paddock. Source: Jordan Hoskinson.

Complementary practices

Foliar applications are just one small part of supplying crops with the nutrients and environment they need for healthy, resilient plant growth and for building soil and landscape health. The Robinsons and Hoskinsons have both implemented a number of other practices that support long term soil health.

One of the most important practices to pair with foliar applications is keeping a close eye on soil fertility. Tom says there is ‘no one recipe, but we go in with a bit of everything’. Keeping track of soil health can mean knowing when to address crop nutrition ‘down the slot’.
A soil fertility approach driven by microbes and targeted crop nutrition is best complemented by practices that minimise soil disturbance. The Robinsons have a long history of zero-till management, which helps them retain soil structure and moisture in their dry climate. Soil moisture helps keep soil biology and ‘living, active mineralisation’ going for as long as possible. Building on zero-till and preserving the progress they’ve made with their soil health, Tom and Cassi have used full stubble retention, a stripper header and a disc planting system for over a decade.
Both the Hoskinsons and Robinsons integrate livestock into their cropping systems whenever possible to gain an in-house supply of manure and to support biological nutrient cycling. Jordan and Karen have also started a new business, ‘Paddock Peckers’, that produces pastured eggs by moving laying hens around the paddocks in mobile tractors. They’ve noticed the difference in soil life and fertility in areas once the chickens have moved through. It’s a process to figure out a system that will work across the farm, but they aim to have an integrated system of sheep, chickens and cropping, where each enterprise supports growth and fertility in the others.

Further learning

Explore our series of practice guides

Biological Seed Treament
A step-by-step guide for growers interested in exploring this low cost, low risk practice to build soil health and promote healthy crops, with examples from two growers already doing it.

Multispecies Cropping
A step-by-step guide for growers interested in building soil health, improving nutrient cycling and boosting productivity, with examples from three growers already doing it.

Foliar Applications
This guide is designed to help you decide if foliar applications could be a useful part of your crop nutrition and approach to inputs and to help you get started.

Biological Fertilisers
This practice guide introduces some of the benefits of biological inputs and fertilisers and offers practical insights into how they can be used in broadacre farming.

Next guides coming soon!
Follow us on socials, or sign up to our newsletter to hear about our next releases!

Multispecies Cropping
Check out our ‘how to’ video series on Multispecies Cropping. Farmer Grant Sims shares why he started and how de does it.

Resources and tips recommended by the farmers in this guide

Building soil health and farm resilience is an ongoing journey of learning, observing and adapting practices to what works best in your specific context and goals.

Tom jokingly calls learning about plant nutrition the ‘rabbit hole’, and both he and Jordan recognise that the adjustments they’re making with foliar applications are just part of building a knowledge base around plant health and soil fertility. Each season brings new insights about their soil and cropping systems. They both emphasise the importance of seeking trusted advice when you’re getting started to help guide you along the way.

Here are some resources and tips for further learning recommended by the farmers in this guide:

Joel Williams, plant and soil health educator, Integrity Soils
Mark Tupman from Productive Ecology
Lower Blackwood Land Conservation District Committee resources
Graeme Sait’s Nutrition Farming Podcast
John Kempf’s Regenerative Agriculture Podcast

References used in this guide

Other resources from Soils for Life

Join a discussion group
Learn from other like minded farmers in one of our Cropping Discussion groups or follow our guide to start your own.

Listen to the Soils for Life Podcast and webinars
Check out our cropping episodes and this interview with Joel Williams on small steps for big change in cropping, as well as this webinar with Mark Tupman and Tom Robinson on getting started with foliars.

What did you think of this guide?

Thank you for reading the practice guide! We would love to know whether you found the guide useful. Please take a minute tell us more.

This project is jointly funded through the Australian Government’s Future Drought Fund and Soils for Life.

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If you have any questions, get in touch at [email protected].

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Practice Guide: Foliar Applications

Practice Guide: Foliar Applications

PART OF A SERIES OF PRACTICE GUIDES TO USE IN YOUR REGENERATIVE CROPPING TOOLSET | LAST UPDATED: FEBRUARY 2025

Overview

Other guides to check out

What are foliar applications?

Diagram 1. A cross section of a leaf, showing some of the known points of absorption for nutrients via foliar application. Source: Soils for Life.

Location: Wiradjuri Country, Kikoira, New South Wales

Regional Climate: Hot dry summer, cold winter/temperate sub-humid

Average Annual Rainfall: 450 mm

Property Size: 800 ha (around 240 ha cropping)

Elevation: 240 m

Social Structure: Family farm

Enterprise Type: Broadacre cropping, merino sheep and pasture-raised poultry

Foliar applications: Micronutrients, some macronutrients and biostimulants.

Soils: Predominantly calcarosols and kandosols. Varies from heavy clays, loams and self-mulching clays, as well as some red granite country.

Location: Kaurna and Ngadjuri Country, Hoyleton, South Australia

Regional Climate: Warm summer, cold winter/mediterranean

Average Annual Rainfall: 325-425 mm

Property Size: 1,214 ha

Elevation: 190 m

Social Structure: Family farm

Enterprise Type: Mixed broadacre cropping (growing a variety of crops including wheat, lentils, barley, canola and others). Cattle and mixed species winter or summer annuals for grazing or hay, as well as a Highland cattle stud

Foliar applications: Micronutrients, some macronutrients and biostimulants.

Soils: Mostly calcarosols and chromosols. Red brown earth loam and loam clays, with some heavier clay up under the hills.

What are the benefits?

A targeted method for applying timely crop nutrition and other beneficial inputs that support optimised plant and soil health and resilience.

How to apply foliars

Image 3. Spray equipment that is used for foliar applications at Robinsons Farm. Source: Tom Robinson.

Start with crop monitoring

Ingredients and rates

Mixing the ingredients

Image 4. Due to the scale of foliar operations at Robinson Farms, micronutrients are often mixed in individual shuttles and then drawn from each to combine in the spray tank. Source: Tom Robinson.

Equipment and application

Image 5 and 6. For mixing, the Robinsons keep water agitated by circulating it from the top to the bottom of shuttles with a standard firefighting pump. They have also converted spa-pool pumps for heating water to improve the solubility of some ingredients, such as urea. Source: Tom Robinson.

Finances

Table 4. An indication of some per hectare costs from Tom and Jordan that you might expect of foliar products and application costs.

Indicators of success

Image 8. Visual assessment of foliars at the Hoskinsons farm, Dirragarra Ag. You can see the left side of the paddock where a foliar was sprayed has subtle visual differences with the right side of the paddock. Source: Jordan Hoskinson.

Complementary practices

Further learning

Explore our series of practice guides

Biological Seed Treament A step-by-step guide for growers interested in exploring this low cost, low risk practice to build soil health and promote healthy crops, with examples from two growers already doing it.

Multispecies Cropping A step-by-step guide for growers interested in building soil health, improving nutrient cycling and boosting productivity, with examples from three growers already doing it.

Foliar Applications This guide is designed to help you decide if foliar applications could be a useful part of your crop nutrition and approach to inputs and to help you get started.

Biological Fertilisers This practice guide introduces some of the benefits of biological inputs and fertilisers and offers practical insights into how they can be used in broadacre farming.

Next guides coming soon! Follow us on socials, or sign up to our newsletter to hear about our next releases!

Multispecies Cropping Check out our ‘how to’ video series on Multispecies Cropping. Farmer Grant Sims shares why he started and how de does it.

Resources and tips recommended by the farmers in this guide

Other resources from Soils for Life

What did you think of this guide?

This project is jointly funded through the Australian Government’s Future Drought Fund and Soils for Life.

For more information

Follow us for the latest

Previous PostPractice Guide: Biological Inputs and Fertilisers

Next PostPractice Guide: Multispecies Cropping

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**Location: Kaurna and Ngadjuri Country, Hoyleton, South Australia**

Biological Seed Treament
A step-by-step guide for growers interested in exploring this low cost, low risk practice to build soil health and promote healthy crops, with examples from two growers already doing it.

Multispecies Cropping
A step-by-step guide for growers interested in building soil health, improving nutrient cycling and boosting productivity, with examples from three growers already doing it.

Foliar Applications
This guide is designed to help you decide if foliar applications could be a useful part of your crop nutrition and approach to inputs and to help you get started.

Biological Fertilisers
This practice guide introduces some of the benefits of biological inputs and fertilisers and offers practical insights into how they can be used in broadacre farming.

Next guides coming soon!
Follow us on socials, or sign up to our newsletter to hear about our next releases!

Multispecies Cropping
Check out our ‘how to’ video series on Multispecies Cropping. Farmer Grant Sims shares why he started and how de does it.

Want our seasonal
e-newsletter? Sign up here!