Biostimulants in UK Agriculture
Biostimulants are used to influence natural plant or soil processes in ways that can support crop development, nutrient use and tolerance to environmental stress.
They are increasingly being used alongside conventional agronomy in UK crops, but their value depends on choosing the right product for the crop, timing and situation.
Biostimulants are a broad group, with different products acting in different ways. Understanding their mode of action and the evidence behind them is therefore important when deciding where they fit within a crop programme.
What are biostimulants?
Biostimulants are products designed to influence plant or rhizosphere processes rather than simply supplying nutrients or directly controlling pests and diseases.
Depending on the product, they may be used to support nutrient-use efficiency, root development, crop establishment, tolerance to abiotic stress or other aspects of plant growth and development.
Biostimulants can be based on a wide range of materials, including seaweed extracts, peptides, amino acids, humic substances and beneficial microorganisms.
Because the category is so varied, biostimulants should not be treated as a single type of input. Their performance and appropriate use depend on the specific technology involved.
How do biostimulants work?
Different biostimulants act through different plant or soil processes.
Some influence root development or nutrient uptake, while others affect plant signalling, stress responses or interactions between roots and microorganisms in the rhizosphere.
The mode of action matters because it determines where a product is most likely to add value.
A product intended to support crop establishment, for example, may be positioned differently from one designed to support a crop through drought, waterlogging or another period of environmental stress.
Biostimulants and fertilisers: what is the difference?
Fertilisers supply nutrients required for crop growth.
Biostimulants, by contrast, are intended to influence plant or soil processes in ways that help the crop make better use of available resources or respond more effectively to particular conditions.
Some products contain both nutritional and biostimulant components, so the distinction is not always absolute.
Where nutrient supply is limiting, a biostimulant should not be seen as a replacement for an appropriate fertiliser programme.
Biostimulants for rooting and crop establishment
Root development has a major influence on a crop's ability to access water and nutrients.
Some biostimulants are designed to support early root growth, root architecture or activity within the rhizosphere.
This can be particularly relevant where establishment conditions are difficult or where the crop needs to develop a stronger root system before periods of higher demand.
The response will depend on crop, soil, weather and product, so claims around rooting should be supported by evidence for the specific biostimulant being used.
Biostimulants and nutrient-use efficiency
Some biostimulants are positioned around improving nutrient uptake or nutrient-use efficiency.
This may be achieved by influencing root development, nutrient transport, microbial activity or plant metabolism, depending on the technology.
The objective is to help the crop use available nutrients more effectively rather than simply adding more nutrient to the system.
They should therefore complement sound nutrient planning, soil analysis and crop monitoring rather than replace them.
Biostimulants for abiotic stress
Drought, heat, cold, waterlogging and salinity can all affect normal crop function.
Some biostimulants are designed to support the plant's natural response to these abiotic stresses.
Depending on the product, this may involve changes in root development, plant signalling, antioxidant activity, water use or other physiological processes.
Biostimulants cannot remove the underlying cause of stress, but they may help the crop tolerate or recover from difficult conditions where there is evidence to support their use.
Biostimulants and plant defence
Some biostimulants are designed to influence natural plant defence mechanisms.
These products may act as elicitors or primers, stimulating plant signalling pathways before or during periods of stress.
This can include responses such as reinforcement of cell walls, production of defensive compounds or activation of other physiological defence processes.
Where disease control is required, these products should be positioned alongside appropriate crop protection rather than treated as direct replacements for fungicides unless the product is specifically authorised for disease control.
Seed treatment biostimulants
Biostimulants can also be applied to seed before drilling.
Seed-applied products may contain microorganisms, peptides, amino acids or other compounds intended to support establishment, early root growth or crop resilience.
The early growth period can be particularly important where crops are being established into colder soils, later drilling windows or other challenging conditions.
As with foliar products, performance should be assessed on the basis of replicated evidence and the intended use of the individual product.
Types of agricultural biostimulant
Seaweed extracts
Seaweed-based biostimulants contain a range of naturally occurring compounds that can influence plant growth and stress responses.
Products vary considerably according to seaweed species, extraction process, formulation and concentration.
This means two products described as seaweed biostimulants may not necessarily have the same mode of action or performance.
Peptides and amino acids
Peptide- and amino-acid-based products can influence plant metabolism, signalling and stress responses.
Some are used to support plant defence mechanisms, while others are positioned around growth, recovery or nutrient-use efficiency.
The effect depends on the composition and technology within the individual product rather than the category alone.
Microbial biostimulants
Microbial biostimulants contain beneficial microorganisms such as bacteria or fungi.
Depending on the organism, they may interact with plant roots or the rhizosphere and influence nutrient availability, root development or crop growth.
Successful establishment of microbial products can be influenced by soil conditions, temperature, moisture and compatibility with other inputs.
Humic and fulvic substances
Humic and fulvic substances are derived from organic materials and are used in some products intended to influence soil, root and nutrient interactions.
Their effects depend on the source, formulation, rate and method of application.
Specialist elicitors and plant-response products
Other biostimulants use specific compounds such as peptides, chitosan or related technologies to trigger particular plant responses.
These products may be used to influence plant defence signalling, stress tolerance or other physiological processes.
The most useful way to assess them is by their demonstrated mode of action and crop response rather than by grouping them together under a broad biostimulant label.
Where do biostimulants fit in UK crop production?
Biostimulants are now used across a wide range of UK crops, including cereals, oilseed rape, potatoes, pulses, vegetables, fruit and vines.
Their role varies between crops and situations.
Potential uses include supporting establishment, improving rooting, helping crops through periods of abiotic stress, supporting nutrient-use efficiency and influencing natural plant defence mechanisms.
The strongest fit is usually where there is a clearly defined crop need and evidence that the chosen technology can address it.
How should biostimulants be assessed?
Biostimulants should be assessed with the same discipline as any other crop input.
The key questions are not simply whether a product is biological or natural, but what it does, where it has been tested and whether it delivers a consistent agronomic or commercial benefit.
Useful evidence can include replicated trials, crop measurements, yield or quality data and an understanding of the product's mode of action.
Seasonal variation is also important. A product designed to help with a particular stress may show a greater response in seasons when that stress is present than in seasons where conditions are favourable.
Using biostimulants as part of an agronomy programme
Biostimulants are most useful when they are integrated into the wider crop programme.
That means considering soil condition, crop nutrition, genetics, crop protection, weather and growth stage alongside the biological product.
A biostimulant should not be used to compensate for an underlying agronomic problem that can be corrected directly, such as severe nutrient deficiency, poor drainage or compaction.
Instead, the objective is to identify where a particular technology can complement the existing programme and improve crop performance or resilience.
Why independent evaluation matters
The biostimulant market includes a wide range of technologies and claims, and performance can vary considerably between products.
Agrii evaluates biological and biostimulant technologies through its research and trials programme before determining where they may have a practical role on farm.
This allows products to be assessed across crops, timings, growing conditions and existing agronomy programmes rather than relying solely on manufacturer claims.
The aim is to understand not only whether a product produces a response, but where that response is most likely to deliver value.
How agronomy advice supports biostimulant use
Choosing a biostimulant starts with identifying the problem or opportunity within the crop.
Your Agrii agronomist can help assess crop condition, soil, nutrition, seasonal risk and the evidence behind available technologies before deciding whether a biostimulant has a useful role.
This may include products aimed at establishment, rooting, nutrient-use efficiency, plant defence or tolerance to environmental stress.
The objective is to use biological technologies where the evidence supports them and where they add value to the wider agronomy programme.