Skip to main content

Biofertilizers, Biostimulants & Biopesticides: Definitions, Differences & Challenges

FERTASA BIO FERTS LOGO Stephanie Roberts, Agronomic R&D Manager for Omnia gave a very informative presentation on the significance and market potential of biostimulants, biofertilizers and biopesticides including a detailed explanation of the definitions, differences and challenges surrounding the use of these products; especially in relation to Group 3 fertilizer registration in South Africa.

There is tremendous interest in this market commercially as worldwide growth of the global stimulants market is expected to reach US$ 3.2 billion within the next five years while the humanitarian challenge increases as agriculture will be expected to feed an extra 400 million mouths in the next five years.

Bioproducts can help to sustainably improve crop yields by reducing crop stress and improving nutrient use efficiency. However this segment of the industry faces challenges of perception as many of these products have been described with dubious claims and a mysterious technical story leading to them being labelled as “muck and magic” in the United Kingdom and “snake oils” in the USA.

Some reasons that these perceptions have arisen:

  • Many products such as kelps and amino acids derived from fish emulsions originated from the organic farming industry which has been associated with not always using the best science available.
  • Many of these products were developed from industry driven R&D and not from Universities, even in Universities there is mistrust relating to these products.
  • Problems of fake products; for example where people are selling caramel colourants and labelling them as “humic”.
  • Unfortunately the genuine products don’t always work and cannot be guaranteed to always give a proper response.

A lesson from the “American Snake Oil” industry 

The original snake oils were used by Chinese immigrants who built the transcontinental railroad in the USA in the 1880’s to ease muscle pain. The Americans realized the potential and used extracts from rattlesnakes when the original snake oil ran out as an alternative, soon unscrupulous businessmen were selling mineral oil as snake oil; which led to snake oil gaining the reputation as something not to be trusted. A hundred years later it was found that Chinese water snakes did indeed carry Omega 3 fatty acids which have anti-inflammatory properties. The lesson from the snake oil industry is that the problem was not related to product but rather to the fake product.

Reference: Roberts 2017

As Roberts explained that the purpose of Group 3 registration is to ensure that biostimulants and biofertilizers aren’t registered as Remedies but as fertilizers and that biopesticides remain registered as Remedies. It is most important to ensure that only proven biostimulants and biofertilizers are marketed to farmers and for the industry to validate the products being sold so that the market is not destroyed by non-regulated non proven products.

The definition of Biostimulants according to the current Group 3 regulations of Act 36: “A fertilizer containing natural or synthetic substance(s) or organism(s) or maintain(s) the growth or yield of plants or the physical, chemical or biological condition (fertility) of the soil; and “soil improver” shall have the same meaning“.

The major challenge facing the biostimulant market is that currently worldwide there is no legally agreed definition of these products, which is critical to fully understand and differentiate between products. Roberts used the description of biostimulants used by the South African Bio Product Organization who work closely with the biopesticide and biofertilizer society which clearly defines and differentiates these products:

“Biostimulants” are products that stimulate natural processes in the plant or around the roots to enhance nutrient uptake, nutrient efficiency, increased tolerance to abiotic stress, and crop quality, vigour and yield. Although biostimulants improve efficiency and may lead to slight reductions in fertilizer applications these products are definitely not a replacement for a balanced fertilizer program.

Typical Biostimulants:

  • Marine Macroalgae Extracts e.g. Kelp
  • Plant Extracts e.g. Brassinosteroids
  • Protein Hydrolysates & Amino Acids
  • Humic & Fulvic Acids

“Biofertilizers” are micro-organisms that stimulate natural processes in the plant or around the roots to enhance nutrient uptake, nutrient efficiency, increased tolerance to abiotic stress, and crop quality, vigour and yield.” – Essentially the same definition as a biostimulant except that live microbes are involved.

Typical Biofertilizers:

  • AMF (Arbuscular Mycorrhizal Fungi)
  • Free-living N-Fixing e.g. Azosporillum
  • Hormone-releasing e.g.Bacillus
  • P-solubilizing e.g. Pseudomonas

These products are widely described as PGPR’s (Plant Growth Promoting Rhizobacteria), however it has been found that it doesn’t necessarily have be a rhizobacterium, overseas research has found that even foliar organisms have been found to help with processes such as nitrogen fixation in crops.

Microbial biopesticides and insect biopesticides should really be referred to as biocontrol agents or as a bioremedies and not as biopesticides in terms of South African legislation.

Typical Microbial Biopesticides :

  • Trichoderma species
  • Bacillus species
  • Bacillus thuringiensis
  • Beauvaria bassiana

It’s important to make the distinction between microbes that fertilize versus those that control pests and diseases; and Roberts explained that this is technically where grey areas arise:

  • Trichoderma and Bacillus species which are registered as Remedies but could also fall into Group 3 as they display both pathogen antagonistic and plant symbiotic effects, registration will depend on the product that is being registered and claims to be made on the product.
  • Kelp – Group 3 vs Synthetic PGR’s – Remedy.  Some kelp products are registered as remedies however based on the Group 3 regulations these products should be registered under Group 3, it is important to distinguish these products from the synthetic products which should be registered as remedies. The reason for this is that the bio stimulant effect of kelp is not necessarily limited to auxins and cytokinins as there are also other actives present in the kelp that play a role.  Synthetic PGR’s are more risky as they are used to thin fruit and as desiccants; any product that has the potential to do damage to a crop even if the damage is commercially beneficial needs to be registered as a Remedy.
  • Biofertilizers – Group 3 versus Legume Inoculants – Remedy. Bio fertilizers are supplied to enhance chemical fertilizers not to replace them, while legume inoculants specifically are intended to replace chemical fertilizer. Should the inoculant not work then the farmer will have a crop failure unless he applies additional nitrogen fertilizer. The onus comes back to the companies to demonstrate that the product is definitely going to work as the farmer is potentially gambling his entire yield that the product is going to work.
  • Group 1 & 2 Fertilizers + Biostimulants – What happens when a products fall under the definition of Gr 1& 2 but also contains bio stimulants, according to the Act 36 regulations published on 8 September 2017; up till now this has not been clarified.


  • The challenge of the negative perceptions of bio-products which necessitates why the industry needs to work together to get products registered to ensure credibility.
  • Group 3 registration will protect the reputation of legitimate biostimulant / biofertilizer products, protects the industry and ensures the profitability of the farmers who use the products.
  • Biostimulants are substances that enhance crop growth but don’t qualify as essential plant nutrients as recognized under Group 1 and Group2 fertilizers.
  • Biofertilizers are live microbes whose primary effect is to enhance crop growth.
  • Biopesticides are live organisms whose primary effect is to directly control crop pests and diseases.
  • If a product is designed to be helpful to plants and soil it most likely will be registered as a Group 3 Fertilizer.
  • If a product is harmful to pests or poses a high risk to crops then it needs to be registered as a Remedy.

Challenges going forward

  • How do we verify the active content in biostimulant products such as kelp and humics as there currently is no agreed methodology in RSA to define active content within these products.
  • The representative crop groups for claims has not been specified for Group 3, the cost of running trials on a wide variety of crops will have a impact on cost of products in the future. Group 3 products impose a lover risk than Remedies will the industry be allowed to use wider crop groups to verify claims and reduce costs?
  • There is a need to clarify the difference between a remedy and a fertilizer with products such as baccilus and trichoderma.
  • The Agreement on acceptable evaluation techniques on demonstrating how these products work.

Roberts concluded “The science of these products is developing faster than the legislation can be written which necessitates the importance of the industry to work with government to be able to supply reliable products to farmers.”

Paper presentation: