The Issue

Applied to soils or crops, biostimulants enhance biological processes that help plants use nutrients more efficiently, grow stronger, healthier plants and better withstand stress such as drought, salinity, or disease.

Currently there is no regulation of biostimulant product use in Australia. Historically some products have been promoted to growers with very limited scientific evidence. Grower experiences have been very mixed, with a high level of skepticism amongst, farmers, agronomists and rural merchants.

However, the evidence base for the use of some biostimulant products in agriculture continues to build. 

Plant biostimulants can be placed into five compositional categories: 

A. Microbial based biostimulants

1. Live microbial products

2. Complex products based on non-living microorganisms and their metabolites

B. Algal or plant extract biostimulants

1. Aquatic plant extracts

2. Microalgal and macroalgal extracts

3. Higher plant extracts

C. Complex carbon-based biostimulants

1. Humic substances. These can be mined natural deposits or synthesised from composts or organic agricultural by-products. They are primarily composed of three fractions (humic acids, fulvic acids, and humin). Sources of humic substances are commercially harvested from terrestrial deposits which include, but are not limited to, Leonardite, oxidized lignite, oxidized sub-bituminous coals, humalite, carbonaceous shales (including humic shale), peat, and sapropel.

2. Other complex carbon-based residuals and extracts (e.g., vermicompost/worm castings, compost waste materials, biochar etc.), or liquid extracts derived from these materials (e.g., compost tea, etc.).

D. Protein hydrolysate biostimulants (containing peptides and free amino acids) - derived from plant, animal, or microbial protein feedstock

1. Manufactured by chemical hydrolysis. 

2. Manufactured by enzymatic hydrolysis.

E. Defined molecules purified from minerals, plants, animals, microbes, or obtained by synthesis. 

These may include: 

1. Organic molecules that are not defined as humic substances (e.g., amino acids, polyamines, polyphenols, betaines, oligosaccharides, alginates, carboxylic acids, fatty acids, chitin, chitosan, etc.)

2. Minerals that may not be recognized as plant nutrients (e.g., silicon, selenium, etc.).

In an effort toward improving transparency and consistency in biostimulant labelling, Fertilizer Australia has developed a voluntary Code of Practice (CoP) for the labelling of biostimulants. The first version of the code focuses on microbial based products and humic substances. The intention is to add other biostimulant categories in subsequent versions of the code. 

This industry-led initiative is designed to support growers, agronomists, and rural advisors by promoting clear, accurate, and consistent product information in a market that’s growing rapidly, but often lacks clarity. Until now, there’s been little standardisation in how these products are described in Australia, which create opportunities for confusion in the minds of users.

Fertilizer Australia’s new CoP aims to change that, making it easier for growers to understand what biostimulants contain, and how to use them effectively.