Practice Guide: Biological Seed Treatments
PART OF A SERIES OF PRACTICE GUIDES TO USE AS PART OF YOUR REGENERATIVE CROPPING TOOLSET | LAST UPDATED: SEPTEMBER 2024
Overview
Applying biological seed treatments is a common first step for farmers interested in improving soil health and farm resilience, often part of a larger strategy to enhance soil biology, increase nutrient cycling and reduce or eliminate insecticides and fungicides.
Farmers use biological seed treatments to give their plants the best possible start. Biological seed treatments can include microbes, biostimulants and sometimes nutrients. They are applied to bare seed, and are intended to enhance root development and the microbial relationship between the growing plant and the soil.
This guide is an introduction to biological seed treatments. It covers the benefits, ingredients, application methods, complementary practices, monitoring outcomes and real-life examples.
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 biological seed treatments?
Biological seed treatments are liquids or powders that can contain a combination of microbes, biostimulants and sometimes nutrients or trace minerals. These treatments are applied to the seed prior to sowing and can be mixed or brewed on farm or purchased from credible suppliers. Recipes can be as simple as using compost extracts or vermicast (worm castings), or more complex with a ‘stacked’ approach of using multiple ingredients such as kelp, fulvic acid, humic substances, trace minerals, protein hydrolysates, etc.
Farmers using biological seed treatments
This guide includes examples from two Australian farmers throughout, showing their approach to biological seed treatments in different farming systems.
Will McInnes and his parents farm 1,200 ha at Jacana, 20 km east of Goondwindi, Queensland. They run cattle and grow wheat, barley and sorghum on what Will calls ‘melon hole country’. Will studied engineering at university and returned to the family farm in 2014. He took on management in 2016.
After a significant frost event, Will began looking at how he can improve the farm’s soil health to build more resilience into his system. He has been trialling and implementing various practices to improve his soil biology, including applying biological seed treatments, sowing multispecies cover crops, eliminating insecticides, using minimal fungicides and buffering herbicides with fulvic acid. He applies guano instead of mono-ammonium phosphate (MAP), uses low rates of nitrogen fertiliser and tissue tests his plants to understand nutrient requirements.
Location: Bigambul Country, 20 km east of Goondiwindi, QLD
Regional Climate: Hot dry summer, cold winter/sub-tropical sub-humid
Average Annual Rainfall: 624 mm
Property Size: 1214 ha
Elevation: 230 m
Social Structure: Family farm
Enterprise Type: Mixed cropping and cattle
Soils: Soils either Vertosols or Sodosols, commonly referred to as ‘Melon hole, gilgai country’
Carol and Brian Fitzpatrick farm 2,700 ha in Waitchie, Victoria, west of Swan Hill. They grow dryland wheat, barley, peas, lentils and occasionally oaten hay for export.
Brian comes from a farming background, working on the family farm in southern NSW up until 2007, when he bought land at Waitchie with Carol. Carol has a background as a surveyor and engineer, but left her work with the local council in 2021 to become more involved in the farm. They’ve been pursuing a ‘biological’ approach to cropping by using biological seed treatments, brewing their own biofertilisers, using fulvics, humics and molasses with herbicide and nitrogen applications, and eliminating insecticides and fungicides.
The impetus to experiment with practices to support their soil biology comes from Carol, who has always been interested in organic gardening and tends to a productive quarter-acre vegetable garden that feeds their family.
Location: Wergaia and Wemba Wemba Country
Waitchie, VIC
Regional Climate: Hot dry summer, cold winter/mediterranean
Average Annual Rainfall: 300 mm
Property Size: 2,700 ha
Elevation: 58 m
Social Structure: Family farm
Enterprise Type: Dryland cropping
Soils: Calcarosol soils, often called mallee sand, mallee loam or calcareous earths
What are the benefits?
A low cost, low risk tool to get started building soil health
Boost early growth: Biological seed treatments can encourage early root development, which allows the plant to better access soil moisture and nutrients and to develop a relationship with the soil microbiome. Many farmers who use biological seed treatments observe vigorous germination, strong root development with a fuzzy rhizosheath (see Indicators of success) and resilient seedlings.
Increase plant health: Biostimulants11Biostimulants are any substance or microorganism applied to plants with the aim to enhance nutrition efficiency, abiotic stress tolerance and/or crop quality traits, regardless of its nutrients content- https://www.sciencedirect.com/science/article/pii/S0304423815301850 and micronutrients that are applied to the seed can support the plant in its early weeks of growth.2Jay Ram Lamichhane, David Camilo Corrales and Elias Soltani, “Biological seed treatments promote crop establishment and yield: a global meta-analysis”, Agronomy for Sustainable Development 42 (2022), https://doi.org/10.1007/s13593-022-00761-z. Microbes in and on the seed are important for acquiring nutrients from the soil and producing secondary metabolites that build tolerance to pests, diseases and environmental stresses. Microbes applied to a seed with biological seed treatments, along with the microbes already associated with the seed’s microbiome, can populate the emerging root and continue to grow with the plant for its entire life cycle, forming beneficial plant soil relationships. By supporting a diverse and balanced microbial community in the soil and on the plant, farmers can keep pathogens in check.3 Kanchan Vishwakarma et al., “Revisiting Plant-Microbe Interactions and Microbial Consortia Application for Enhancing Sustainable Agriculture: A Review”, Front Microbiol 11 (2020), https://doi.org/10.3389/fmicb.2020.560406. Conversely, fungicides and insecticides that are applied to the seed through commercial seed pickles can impact these microbial community dynamics.
High bang for buck: What makes biological seed treatments appealing for many farmers is that only a small amount of biological input is required, with targeted application where it is most impactful – on the seed itself. This means good ‘bang for your buck’.
Diagram 1. The role of seed microbiome through the life cycle of a plant. Source: Soils for Life
For Will McInnes, using bare, unpickled seed and introducing biological seed treatments was one of the first things he changed across the farm when he took on management in 2016. Will had been reading up on the importance of soil biology in growing resilient crops and using unpickled seed, learning from the likes of Graeme Sait, Gabe Brown and Grant Sims. Will found it counterintuitive to be treating his seed with fungicide when he was trying to encourage soil biology:
‘If you want mycorrhizal fungi to function in your soil and help your plant out, you can’t put the fungicide on [the seed] like that.’
Will admits to being nervous the first time he sowed bare seed with biological treatment because ‘everyone tells you there’s so many bad things in the soil’, such as pathogenic fungi and insects. Despite the sleepless nights, Will’s first unpickled crop that he coated with a biological seed treatment germinated without a problem. It was convincing enough for him to decide not to use commercial pickle again. He is happy with his plants’ early germination and vigour and understands now that ‘the seed’s quite capable of getting out of the ground and starting a strong life’.
Brian and Carol have never used commercial pickles on their seed even though most of the farmers around them have always done so. Brian felt that because they weren’t putting anything on the seed, it was worth trying a biological seed treatment to see what would happen, as they are always striving for improvement in the quality of the plants they grow. They now treat their seeds every year and they’re happy with the strike rate, vigour and root development of their plants.
How to use biological seed treatments
Changing practices can be daunting. Taking small steps over time rather than going ‘all in’ can help to manage risk and allow your farming system time to adjust. Biological seed treatments are considered to be low risk and low cost, but you can also consider running a few test strips of bare and biologically-treated seed first to find out what works in your context.
Use bare seed
It’s important to start with ‘bare’, good quality seed that hasn’t been coated with a commercial ‘pickle’, fungicide or insecticide. Brian says, ‘If nothing else, drop your commercial seed dressing because it does more harm than good…Put on some worm juice if you like, but bare seed alone is better than the commercial pickle.’
External sourcing: Sourcing bare seed can sometimes be a challenge. It can be helpful to start the conversation with your seed suppliers and get your order in early. You could also draw on your community network to source bare seed from local farmers.
Saving seed: In addition to bare seed, it can be beneficial to save your own seed for sowing. Part of the seed microbiome is inherited from the soil, which means that plants grown from seed you’ve saved will be better positioned to develop microbial relationships suited to your soil type, growing conditions and farming practices.
At Jacana, Will is able to sow untreated seed that he purchases locally, apart from sorghum. For the most part, he chooses to save his own seed based on the premise that the ‘seed is already accustomed to the land it’s been grown in’. Carol and Brian also save their own seed and have recently invested in grading equipment to select for the largest seeds to sow, which can have a greater potential for plant vigour.
Images 6 & 7. Seedling at the Fitzpatrick’s (left, source: Carol Fitzpatrick) and a more established plant at Will’s (right, source: Sarah Fea) that were both treated with biological seed treatment.
Choose your ingredients
Where to begin: There are many different ingredients to choose from when considering biological seed treatments. It can be confusing to know where to begin! As a general rule, soil and plant health educator Joel Williams suggests seed treatments should include:
- One or more ingredients that inoculate (contain microbes); and
- One or more biostimulants or ingredients that provide fuel for the microbes
Many farmers start by using widely available ingredients like vermicast liquid or compost extracts as seed treatments to see how their crops respond. Vermicast and compost extracts are examples of ingredients that act as both inoculants and biostimulants. Carol recommends starting with just a compost extract which, if you make your own, is very low in cost. Ingredients that contain micronutrients, such as trace mineral products purchased from credible suppliers, can also be considered in your biological seed treatment mix. However, micronutrients are arguably not a priority because there are other sometimes more suitable opportunities to provide micronutrients to the plants (such as through foliar applications).
Inoculant
- Compost extract
- Vermicast extract
- Mycorrhizal fungi and Trichoderma products
- Anaerobic microbes
- Commercial legume inoculants
Biostimulant
- Compost extract
- Vermicast liquid
- Seaweed (such as kelp and algae)
- Humic and fulvic substances
- Molasses
- Amino acids
- Protein hydrolysates
Nutrients
- Trace mineral products (avoid using copper on the seed)
Find out more: Check out our article on Working with Bio-amendments to learn about the different ingredients you can use and how four of our case study farmers are working with them as foliar applications, seed dressings and composts, and how they integrate them into larger integrated management decisions.
Brian and Carol use vermicast liquid, a small amount of kelp as an added biostimulant, a mycorrhizal fungi and Trichoderma product (such as Nutri-Life Platform or SureCROP VAM) and often some compost tea or extract in their biological seed treatments. Carol explains that they like to use a mycorrhizal fungi product in their seed treatments because they have hot dry summers and are unable to grow plants year round to constantly host and feed mycorrhizal fungi in their soils. They no longer focus on products containing nutrients because their liquid inject-applied biofertilisers provide the minerals they understand their plants need. They decided to use these products based on recommendations from other farmers and from podcasts.
Will treats his seed with products that act ‘as a nutritional package to help the seed start from a young age and get it what it needs’. His products include trace minerals, humics, fulvic substances, seaweeds, kelps, mycorrhizal fungi and Trichoderma powders, anaerobic microbes and vermicast. He explains that his goal is to get a really wide variety of trace minerals and microbes on the seed in combination with something to chelate to (fulvics and humics) and a fuel source (molasses). The fuel source is important so that the biology can sustain itself while the seed gets going, ‘and then the microbes can establish a relationship with the root zone straight away’. Similarly to Carol and Brian, Will is interested in inoculating his seed with mycorrhizal fungi, which he’s concerned that his soil is lacking. He’s interested in the potential benefits of mycorrhizal fungi to unlock tied up nutrients, particularly phosphorus.
Table 1. Carol and Brian’s seed treatment as of 2024.
Table 2. Will’s seed treatment as of 2024.
Sourcing: Depending on your location, most ingredients can be sourced online or via your local rural supplies store, but it’s useful to ask around to see what’s affordable and locally accessible and what others in your area are using. Consider brewing your own microbes on farm where possible to make the most out of your farm’s indigenous microbial population. These microbes will likely be best suited to your farm and local conditions.
Don’t forget the legumes! If you’re planting legume seed, it’s important you inoculate with rhizobia. Rhizobia are bacteria that optimise legume nodulaton and nitrogen fixation. Different legume plants require different strains of rhizobia and most rural supply stores and seed companies will sell legume inoculant products. Inoculating legume seed is a no-brainer for Brian and Carol, who wished they had started inoculating their legume seed a long time ago. They apply a rhizobia product in addition to their biological seed treatment.
Apply the treatment
Applying biological seed treatments is a fairly straightforward process. You’ll need a tank to hold and mix the ingredients, and ideally a hose and a small pump. You may want to agitate your mix prior to application to stir any sediment that has settled. Most broadacre farmers apply their seed treatments as they’re moving the seed via auger from storage into the truck or seeder the same day that they’re planning to sow (or a day or two earlier). Depending on the ingredients, 5–10 L of seed treatment per tonne of seed is generally considered a good starting point to ensure the seed is well coated but easy to handle with your equipment.
Images 8 & 9. Will Mcinnes’ biological seed treatment set up. Source: Sarah Fea
Carol and Brian apply approximately 20 L of liquid per tonne of seed. They started out using a 44-gallon drum to combine the ingredients, but are now using an old milk vat which holds about 700 L. They use a 2-inch pump, which acts as an agitator, and plug a garden hose into the tank to then spray onto the seed as it’s going up the auger into the truck or grouper. They generally wait an hour until the seed is relatively dry before moving it from the truck into the air seeder. They have found that the quantity and ingredients they use are not too sticky and do not seem to cause problems with equipment.
Will’s approach is similar. He combines the products together in a 20-litre container using an electric paint mixer. He prefers to have the liquid mix set up slightly raised to make the flow of liquid easier. He uses a small water pump to apply the treatment at about 6–8 L per minute, which equates to 10 L per tonne of seed. Will suggests that aiming for approximate quantities rather than exact rates is sufficient when it comes to biological ingredients. He runs a hose from the pump to the base of the auger so the treatment is picked up and applied to the seed as it’s getting fed into the truck to take out to the air seeder. Will is happy to apply his seed treatment a couple days in advance to suit his schedule and equipment.
While the rate at which Will applies his biological seed treatment is not high, he avoids storing wet seed in field bins with cone bottoms because the seed can get stuck. Truck beds or chaser bins have enough airflow for the seed to dry, and he’s had no issues once the seed is in the air seeder.
Tips and Tricks
- Avoid using too much liquid. This will ensure that the seed is easy to handle. Stick to 5–10 L/t of seed as a starting point, or follow the product guidelines if applicable.
- Some ingredients and products are stickier than others. Trial a small amount of seed at a low application rate before applying to large quantities of seed.
- Allowing the seed to dry out for an hour or so before sowing can prevent issues with your seeding equipment. This can be done in the grouper before sowing to prevent sticking or blockages.
- Avoid using field bins with cone bottoms while the seed is wet, as the seed may need more airflow to dry out.
- It can be helpful to have your equipment set up in advance and your ingredients mixed and ready to go to make for a less stressful sowing period.
- Take into consideration that some products may be labour intensive to use (e.g. require a period of fermentation for the microbes to establish). Check the application instructions and plan ahead.
- The quality of some biological products can vary and may have a short shelf life. Be mindful of storing products correctly (e.g. out of direct sunlight and heat).
- Consider brewing your own biological products to save on costs and to ensure that what you’re using is biologically alive, ideally with microbes that are indigenous to your landscape.
Sow appropriately
Biological seed treatments can be more effective if sowing is carried out at an appropriate time (i.e. when temperature and moisture availability is suitable) and the seed bed is well prepared. Using a single disc planter in his no-till system, Will always incorporates fulvic acid or biological stimulants with knock-down herbicide to reduce the impact of the herbicide on soil biology prior to sowing. The Fitzpatricks employ a liquid inject system at sowing, applying a phosphorus biofertiliser (20 L/ha) combined with compost extract and fish hydrolysate (5 L/ha). They make the biofertiliser on farm, following a recipe from agroecologist David Hardwick.
Finances
Biological seed treatments are generally affordable because they only require a small amount of input on a targeted area. However, it’s worth considering the cost of labour required to treat your own seed, and to be mindful of expensive products on the market. Carol’s advice is to steer clear of these products, ‘You wanna get in with baby steps. No point jumping to something that is super expensive, you’ll get disheartened.’ See Tables 1 and 2 under Choose your ingredients for the prices of some ingredients.
The Fitzpatricks blend their own seed treatments to save on costs. Carol says that just starting with homemade compost extract or vermicast is cheap and effective. Not including the compost they make on farm, they now spend about $218 per tonne of seed on various ingredients for their seed treatments, which equates to an average of approximately $8.65/ha (see Table 1). Will’s costs for his biological seed treatments are about $140/tonne of seed or $6.30/ha (see Table 2).
While they are happy with their profit margins, the Fitzpatricks acknowledge that some of the cropping practices they’ve adopted to support their soil biology, such as mixing up seed treatments or brewing biofertilisers, have been labour intensive. But over time they’ve been able to simplify and streamline their processes to a point where they consider the in-field results are worth the effort.
Indicators of success
When you’re adopting a new practice, it’s important to monitor for signs that the practice is worth the time, energy and expense, and to make sure there are no adverse impacts. Regularly observing and taking photos of your crop can be really helpful in the long run. In Will’s experience, ‘If you don’t take photos, you don’t remember’.
Indicators: With biological seed treatments, you want to see that (i) your seeds are germinating in a timely manner and (ii) your seedlings are developing strong roots with a good rhizosheath. The rhizosheath describes the soil that physically adheres to the root system of the plant, creating a fuzzy, hairy appearance. It’s a sign of microbial activity in the rhizosphere (root zone) where soil particles are bound to the roots by biotic glues that are secreted by microorganisms.
Integration into broader monitoring: Monitoring the effectiveness of your seed treatments can be integrated into a larger holistic approach to farm monitoring.
Image 10. Will looks for worms in his soil to know if his management decisions are working. Source: Sarah Fea
Earthworms are Will’s number one indicator that he’s moving things in the right direction. Since taking on management, introducing biological seed treatments and multispecies cover crops and reducing fungicides and salt-based inputs, he has been surprised at the increased number of worms he can find when the conditions are right.
Both Will and the Fitzpatricks use plant tests (sap, tissue or brix) as indicators for how their crops are faring. Will tissue tests at early tillering to check for nutritional imbalances that could be addressed. If there are signs of fungal or disease pressure later in the season, he’ll do another tissue test. Carol and Brian used to do tissue tests sporadically but now sap test every month during the growing season until flowering to identify nutrient imbalances that need to be addressed. They also aim to do a weekly brix test to gauge how well the plant is photosynthesising, and occasionally use their plant sap pH and nitrate meters.
Complementary Practices
Practices like biological seed treatments are more effective if integrated within a larger soil health program of other complementary practices.
Will has been experimenting with multispecies cover crops in his rotations to boost soil biology and nutrient cycling and has been working to address his compaction issues through minimal disturbance and gypsum applications.
In addition to biofertilisers, Carol and Brian apply foliar urea with humics, fulvics and molasses to ‘make the nitrogen a bit more stable’. They also include 1 L of worm juice and 1 L of molasses per hectare when applying herbicides to, as they say, ‘buffer the impact of the herbicide on the soil biology’. Most years they also try to spray out compost extract or compost tea. Carol makes compost on farm and they have also started buying worm castings from Nutrisoil to make extracts.
Insecticides and fungicides have mostly been eliminated at both Will’s and the Fitzpatricks’ because they understand the negative impact these can have on their soil health and biology. However, both Will and the Fitzpatricks will consider using them if totally necessary, though not as a preventive measure. As Carol explains, ‘We’re giving [the plants] what they need but we’re not quite there.’
Image 11. Carol and Brian’s liquid mixing set up that they use for biological seed treatments and biofertilisers. Source: Carol Fitzpatrick
Find out more: Check out our cropping case studies and other practice guides to see what other practices farmers are implementing to build soil health and farm resilience.
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.
Next guides coming soon!
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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
Informative and inspiring people
- Grant Sims, Victorian farmer from Down Under Covers
- Gabe Brown, US farmer
- Nicole Masters, agroecologist and coach from Integrity Soils
- Garry Zimmer, US farmer
- Graeme Sait, QLD educator and co-founder of Nutri-Tech Solutions (specifically the ‘Nutrition Farming’ course)
- David Hardwick, agroecologist and educator from Soil Land Food
- Luke Harrington, soil coach
Useful resources
- The Regenerative Agriculture podcast by John Kempf
Helpful organisations and businesses
- Local and regional farmer organisations such as Vic No Till and Macintyre Ag Alliance
- Nutrisoil
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.
Soils for Life Podcast
Check out our podcast interview with Joel Williams on small steps for big change in cropping.
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