Plant biostimulants are substances and microorganisms (MO) used to enhance plant growth. Different types exist: microbial inoculants, humic acids, fulvic acids, protein hydrolysates and amino acids (AA), and seaweed extracts. According to the ABIC (European Biostimulants Industry Council) the definition is “Plant biostimulants contain substance(s) and/or microorganisms whose function when applied to plants or the rhizosphere is to stimulate natural processes to enhance/benefit nutrient uptake, nutrient efficiency, tolerance to abiotic stress, and crop quality. Biostimulants have no direct action against pests, and therefore do not fall within the regulatory framework of pesticides”

Description of the innovation

Over the last few decades, as agriculture became more intensive, more synthetic fertilisers, pesticides, and herbicides are used to have higher aboveground production. Fertilisers can be based on N, P and K, and are a constant overdosing of nutrients. It is described in the literature, that the increased use of synthetic fertilisers decrease plant biodiversity. This can be explained by the delayed growth of slower-growing plants (the light asymmetry theory), below- and aboveground competition (the total competition hypothesis), and inhibition of germination of certain species due to the increased litter production of the main crop (the litter hypothesis). In addition to plant biodiversity, also soil biodiversity may be affected. It affects C availability, pH, and soil osmolarity, and reduces soil microbial diversity and total microbial biomass.

This increase in global crop production is known as the Green Revolution. Looking more specifically to inorganic fertilisers, plants are unable to take up all N and P inputs as they compete for nutrients with soil microorganisms. When applied in excess or when the input does not match the needs of the plant, problems may occur such as reduced biodiversity in both aquatic and terrestrial ecosystems, increased atmospheric deposition of ammonium, release of nitrous oxide, etc. For this, more focus is going on alternative methods for current agricultural techniques. One of them can be the reduction of fertiliser and replacing it with a nature-based product, such as biostimulants. These can help the soil to develop and increase the soil organic matter. This increases the soil supply and the soil can return back to its original state. 

It is important to know what your soils needs. All types of biostimulants will have another working mechanism and will add something different to the soil. 

Different types of biostimulants

Microbial inoculants are living microorganisms (MO), mainly free-living bacteria, fungi, and arbuscular mycorrhizal fungi, isolated from soil, composted manure, water, and plant (residue). They promote the growth of the plant when applied to the seed, plant surfaces, or soil. This can occur via different processes, such as increasing nutrient supply, increased root biomass, and increase nutrient uptake capacity of the plant. Important to know is that not all microbial inoculants will have the same effects on all types of plants, different soil types and other environmental conditions. When used in combination with conventional agriculture, the substance also needs to be compatible with chemical fertilizer and crop protection.

Humic and fulvic acid are already rich in C, so adding this to the field will directly increase soil C levels. However, a high amount is necessary to have an efficient working mechanism which makes it more interesting to add this in combination with another product. 

Protein hydrolysates are nutritive compounds with functional and/or bioactive properties and multiple applications in areas such as medicine, nutrition, food, and agriculture. These protein hydrolysates can be derived from protein discards such as dairy products, protein-rich seafood wastes and protein from livestock by-products. Within protein hydrolysates, amino acid (AA) composition is important. Within Europe, the use of these products is popular.

Seaweed extracts are already high in micronutrients, such as carbohydrates and proteins, lipids, AA, vitamins, osmolytes, and several plant hormones. In addition, seaweed extracts have a beneficial effect on the activation of native soil microorganisms, including saprophyte bacteria, fungi, and plant growth promoting rhizobacteria (PGPRs). 

Commercial products

In Belgium, the start-up Stam Agro and Ghent University have developed a recipe based on chicken feathers that can strengthen the resistance and growth of plants. Using this as a biostimulant may decrease the use of fertiliser and N, and positively influence C-footprint. Even in periods of drought, less fertiliser is needed to obtain a similar quality and production.

"A biostimulant is a product of natural origin that makes plants grow better and stronger," explains Kris Audenaert, Professor of Plant and Crop at UGent. "Very typically, you can apply them in low concentrations and yet they have a great effect. They ensure that plants can absorb nutrients better, become more resilient, and thus better defend themselves against extreme weather conditions such as drought or prolonged heat."

In Belgium the company Natural Grown sells biostimulants for different sectors. For agriculture specific, they have products for manure upgrading, cultivation support and green manure. 

Impact on farm performance

Socio-economic resilience: Applying a product to the crops/field will come with an extra cost. However, it can be used to replace fertilisers
Animal health and welfare: Less artificial fertiliser is used and plants grow optimally with high levels of nutrients. This will benefit the animals health.
Production efficiency and meat quality: 
Environmental sustainability: 
          - Chicken feathers: reduction of nitrogen emissions and fertiliser use, and circularity: use of a residual waste
          - Using this type of products will improve the soil health and resilience. This may lead to more climate robust soils and crops. 


Article chicken feathers (Dutch)
Castiglione, A. et al (2021). Microbial Biostimulants as Response to Modern Agriculture Needs: Composition, Role and Application of These Innovative Products
Barros-Rodríguez A. et al (2021). Impacts of Agriculture on the Environment and Soil Microbial Biodiversity
Moreno-Hernández J. et al (2020). Strategies for production, characterization and application of protein-based biostimulants in agriculture: A review
Soto-Goméz D. et al (2020). Interactions between agricultural management and soil biodiversity: An overview of current knowledge
Calvo P. et al  (2014). Agricultural uses of plant biostimulants