Biostimulant product types and regulation

Biostimulant product regulation is still in its infancy. Biostimulants are often grouped as either ‘microbial’ or ‘non-microbial’ and further classified by product type.

Regulation of biostimulants

There are no specific requirements for biostimulants in domestic regulations in the UK – as at September 2026.

As a result, products may have been tested to various standards.

Even when tested, tests may not have been conducted under relevant UK crop conditions.

When considering a product, always:

Check the claims
Check the evidence
Check performance in a small area first

If the biostimulant also claims to provide pesticidal or fertilisation activity, these aspects are covered by regulation.

Fertiliser regulations

Unlike a fertiliser, the primary function of a biostimulant is not to supply nutrients.

Some biostimulant products contain added nutrients, which means it acts as a fertiliser, in addition to any biostimulant claims.

The EU fertilising products regulation 2019/1009 defines plant biostimulants as those that:

"Stimulate plant nutrition processes independently of the product’s nutrient content with the sole aim of improving one or more of the following characteristics of the plant or the plant rhizosphere: nutrient-use efficiency, tolerance to abiotic stress, quality traits and availability of confined nutrients in soil or rhizosphere."

In Northern Ireland, products can be CE marked, but this isn’t mandatory.

Pesticide regulations

Biostimulants intended to influence the life processes of plants, such as substances influencing their growth – other than as a nutrient or a plant biostimulant – fall under the EU plant protection products regulation 1107/2009.

Any product marketed as a pesticide in the UK must have a Ministerially Approved Pesticide Product (MAPP) number.

Common biostimulant product types in the UK

Plant biostimulants can be split into two broad categories:

Microbial or biological, which are based on living organisms, such as fungi or bacteria
Non-microbial, which are based on non-living materials

The following tables provide an overview of the main product types, based on what they contain.

They do not indicate efficacy.

Microbial

Product type	Description
Arbuscular mycorrhizal fungi	Common type of endomycorrhizal fungus that forms a symbiotic association with plant roots. An example is Rhizophagus irregularis.
Non-pathogenic fungi	A wide range of fungal species that have no direct pathogenic effect on plants, such as Trichoderma species.
Microalgae	Microscopic single cells found in both freshwater and marine systems.
Plant growth promoting bacteria	Bacteria that influence plant growth, which can be associated with plant roots or with above-ground parts of plants. This group includes nitrogen-fixing bacteria.
Cyanobacteria	Photosynthetic bacteria, sometimes described as blue-green algae, that can produce biologically active molecules with biostimulant activity claims.

Non-microbial

Product type	Description
Amino acids	The building blocks of proteins. Products may contain one or mixtures of amino acids.
Seaweed extracts	Extracts made from marine seaweeds or macroalgae. They contain a complex mixture of compounds, which can vary with the seaweed species and how the extract is produced.
Humic and fulvic acids	Complex organic substances derived from the decomposition of plant and microbial material.
Protein hydrolysates	Mixtures of peptides and amino acids made by breaking down proteins, commonly from plant or animal sources. Their composition depends on the starting material and the hydrolysis process used.
Synthetic or chemical biostimulants	Manufactured chemical compounds with claims of plant biostimulant activity. For example, non-essential chemical elements, such as silicon.

Important considerations

Products can have very different compositions, formulations, modes of action and levels of evidence for efficacy, even within the same group
Products are marketed under various terms, such as biofertilisers, microbial inoculants and soil biology products
Products may be formulated for use on soil, seed, the plant’s rhizosphere or foliage
Product mixtures may combine different product types
Some product are derived from mammalian tissue by-products, including pork and beef material – check that your trade customers or buyers are happy for you to use such materials
If using a biostimulant containing microorganisms, consider the environment in which they will be used
Carefully follow product labels for time and rate of application
If necessary, consult a professional agronomist

Further information

Go back to the biologicals homepage

Topics:

Nutrition

Sectors:

Cereals & Oilseeds