Referring to Professor Dujardin review*, the word biostimulant “was apparently coined by horticulture specialists for describing substances promoting plant growth with-out being nutrients, soil improvers, or pesticides”.

According to Professor du Jardin, the first definition of biostimulants seems to be due to Zhangand Schmidt in 1997 who defined them as “materials that, in minute quantities, promote plant growth”. Since the beginning it appears that biostimulants “are described as substances promoting plant growth without being nutrients, soil improvers, or pesticides” and defined “by what they do more than by what they are”.

Professor du Jardin notes that in scientific literature, the word “biostimulant” was defined for the first time by Kauffman et al. (2007) in a peer-reviewed paper: “biostimulants are materials, other than fertilisers, that promote plant growth when applied in low quantities” completed by the fact that “Biostimulants are available in a variety of formulations and with varying ingredients”.

First focus was on chemical products, and it appeared that the biostimulants action could also be in response to bacteria and fungi, and therefore needed to be added to the definition. 

In order to create a harmonized definition, Professor du Jardin underlines some mains characteristics:

  • The nature of biostimulants is diverse 
  • The Physiological functions of biostimulants are diverse  
  • The Agricultural functions of biostimulants are to “enhance nutrition efficiency, abiotic stress tolerance and/or crop quality traits” 

Professor du Jardin concluded that “any definition of biostimulants should focus on the agricultural functions of biostimulants, not on the nature of their constituents nor on their modes of actions” before   proposing as definition : « A plant biostimulant is 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 » which really close to the final regulatory definition in Europe. (EU REGULATION 1009/2019)

*Patrick Dujardin, Plant biostimulants: Definition, concept, main categories and regulation – 2015 in Biostimulants in Horticulture – Scientia Horticulturae Volume 196, 30 November 2015, Pages 3-14 


EU 2019/1009

In 2009, work started in Europe to lay down rules on making available on the market all kinds of fertilizing products, including biostimulants.

Finally, after ten (10) years of consultation, writing, discussion and time for validation and signature process, the Regulation (EU) 2019/1009* on fertilising products was published on the Official Journal of the European Union the 25 of June 2019. This text will be fully applicable on the 16 of July 2022.

Europe decided to define biostimulants by a functional approach with four kind of functions/claims. The harmonized definition of a biostimulant is “a product stimulating 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:

  • (a) nutrient use efficiency
  • (b) tolerance to abiotic stress
  • (c) quality traits
  • (d) availability of confined nutrients in soil or rhizosphere”

This definition is associated with a clarification that biostimulants are fertilizing products and are not plant protection products.

The text also defines which component material can be used (and only these) to produce biostimulants like “Plants, plant parts or plant extracts” or “Micro-organisms”. These categories of materials are called “Component Material Categories” (CMC). Eleven (11) CMC are defined in the Regulation. For Micro-organisms (CMC 7), only four (4) are listed in the Regulation: Azotobacter spp., Mycorrhizal fungi, Rhizobium spp. and Azospirillum spp.

In order to ensure the compliance with all the Regulation requests, standards are in process of  being developed prior the full application of the Regulation in July 2022. (STANDARDIZATION: CEN/TC 455)

*Regulation (EU) 2019/1009 of the European Parliament and of the Council of 5 June 2019 laying down rules on the making available on the market of EU fertilising products and amending Regulations (EC) No 1069/2009 and (EC) No 1107/2009 and repealing Regulation (EC) No 2003/2003


Until recently, there has been no specific regulation for biostimulants in the US, but some great progress has been made.

On December 20, 2018, the Agriculture Improvement Act of 2018, received President Donald Trump’s signature and became law.

During 2019, the Secretary shall submit a report on plant biostimulants to the President and Congress that identifies any potential regulatory, non-regulatory, and legislative recommendations, including the appropriateness of any definitions for plant biostimulant, to ensure the efficient and appropriate review, approval, uniform national labeling, and availability of plant biostimulant products to agricultural producers. This report will be made after different consultations of the Administrator of the Environmental Protection Agency, the several States, industry stakeholders.

The current definition of plant Biostimulant is a “substance or micro-organism that, when applied to seeds, plants, or the rhizosphere, stimulates natural processes to enhance or benefit

  • nutrient uptake,
  • nutrient efficiency,
  • tolerance to abiotic stress,
  • crop quality
  • or yield”

Other Countries

USA and Europe are the two area where biostimulants are defined and regulated. But, in other regions, biostimulants are covered by national laws under different categories (organic fertilizers, biofertilizers, Plant Growth Enhancer or Plant Strengthener. Some examples:

China is still on the way to achieve a definition of biostimulant, but at this date there is no consistent definition. Products are classified as fertilizers. Some Chinese standards cover some topics.

In India, the main categories for biostimulants are Biofertilizers and Organic Fertilizers, under the Fertilizer Control Order (FCO), 1985. Biofertilisers means the product containing carrier based (solid or liquid) living microorganisms which are agriculturally useful in terms of nitrogen fixation, phosphorus solubilisation or nutrient mobilization, to increase the productivity of the soil and/or crop.

In South Africa, the Fertilizer regulation (2017) consider biostimulant as Fertilizer group 3; which is a natural or synthetic substance or organism/s that improve/s the growth or yield of plants or the physical, chemical or biological condition of the soil. It includes seaweed, organic acids, biofertilizers, PGPR, fertilizer coatings and moisture absorption products. In a guideline published in June 2019, “Biofertilizer”, “Plant Biostimulant”, “Plant Growth Enhancer” or “Plant Strengthener” is any substance or micro-organism or combination thereof which is applied to seed, plant or root environment capable of modifying, and improving, plant development through a collection of different mechanisms of action.

In Brazil, the Lei 6.894/1980 (LEI ORDINÁRIA) classify biostimulants as:

  • Inoculant: substance containing microorganisms with the action favorable to plant development
  • Stimulant or biofertilizer: product containing active ingredient capable of improving, directly or indirectly, the development of plants.

In Mexico, no reference to biostimulants in current Mexican legislation published in 2004 but could be classified as Microbial Inoculants for seed treatments or direct soil application, or as Non Synthetic Fertilizers or Non synthetic PGŔ



ISO/TC 134 – Fertilizers, Soil Conditioners, and Beneficial Substances

The International Organization for Standardization (ISO) is an independent, non-governmental international organization with a membership of 164 national standards bodies. Through its members, it brings together experts to share knowledge and develop voluntary, consensus-based, market relevant International Standards that support innovation and provide solutions to global challenges.

Since December 2018, the ISO Technical Committee 134 has been charged with standardization in the field of fertilizers, soil conditioners and beneficial substances, that is, materials whose addition is intended to ensure or improve the nourishment of cultivated plants and / or to improve the properties of soils, and the efficient use thereof. In fact, the enlargement on beneficial substances is a positive sign on the global interest on biostimulants.

The standard ISO 8157:2015 defines beneficial substance or elements as “substance or element other than primary, secondary, or micronutrient that can be demonstrated by scientific research to be beneficial or may be essential to one or more species of plant, when applied exogenously”.

In the same standard, a proposal for Plant biostimulant has been discussed and could be defined as : “substance(s) and/or micro organism(s) whose function  independent of the nutrient content, when applied to seeds, plants or the rhizosphere is to stimulate natural processes to enhance/benefit one or more of the following :

  • nutrient uptake,
  • nutrient efficiency,
  • tolerance to abiotic stress,
  • crop quality,
  • yield.”

Two dedicated Working Groups have been created to develop ISO standards for beneficial substances (including biostimulants) and for microorganisms. By this way, the characterization, the efficacy and the safety will be harmonized at the global level and will facilitate the trade of biostimulants.


CEN/TC 455 – Plant Biostimulants

The European Committee for Standardization (CEN) develops and sets European standards (ENs) that are applied across the whole of the European single market. CEN brings together the national standards agencies of 34 countries and a network of thousands of technical experts from business federations, commercial and consumer organizations, environmental groups and other societal stakeholders.

It will be mandated by the European Commission to develop standards supporting the implementation of the fertilising products regulation (UE n°2019/1009) and in this context, CEN has created a Technical Committee CEN/TC 455 on Plant Biostimulants which the scope “Standardization of sampling, denominations, specifications (including safety requirements), marking and test methods allowing the verification of product claims for plant biostimulants, including micro-organisms. Plant biostimulants are products, based on substances and/or microorganisms, stimulating 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: – nutrient use efficiency; – tolerance to abiotic stress; or – crop quality traits; and may be applied to plants or soils. Excluded are plant protection products, fertilizers, liming materials, soil improvers, growing media, and agronomic additives that are already covered by standardization at European level.”

To reply to the request of the European Commission, the European experts decided do created 5 Working Groups

  • Sampling
  • Claims
  • Pathogenic and non-pathogenic microorganisms
  • Other safety parameters
  • Labelling and denominations


The first EN standards are expected in first semester 2022 and all harmonized standards by the end of April, 2024.