Welcome to the Biostimulants course.

Study all sections below before taking the final test.

Lesson Notes

Biostimulants - Study the various components that make up biostimulants

Benefits - Understand when, where and why biostimulants should be used


Biostimulants are either natural or synthetic substances that can be applied to turf and soil. These substances are derived from a diverse range of microbial and non microbial components, these include humic acids, seaweed extracts, hormones, enzymes. The raw materials that are used in Biostimulant production help with vital and structural processes in order to influence plant growth through improved tolerance to abiotic stresses and increasing turf quality. A big benefit of using Biostimulants is that fertiliser applications are reduced. In brief Biostimulants are defined by what they do and not what they are, they stimulate growth, but they also do much more, they can assist turfgrass surviving long periods of stress either through heat, drought, disease or high salinity situations.


Biostimulants as mentioned can in small quantities stimulate plant growth. For maximum effectiveness biostimulant applications can be started from early season, before the onset of stress and when the plant is growing; eg Feb, March if temperatures allow some can be used all season. Using biostimulants can reduce applications of pesticides, fertilisers, water and other controls used to combat stresses which often carry a negative stigma. Most biostimulants are natural and not harmful to the environment, so going green is possibly more achievable.


The use of Biostimulants are extremely beneficial to turf, especially with the high demands of our sports turf surfaces are always increasing. Feeding turf to perform can prove difficult if environmental issues prevent this. Biostimulants in small amounts, work by stimulating plant nutrition processes independently of the products nutrient content, this improves more efficient use of nutrients and can also assist with the use of confined nutrients in the soil. Other benefits are enhanced microbial activity, lowers leaching and improved soil structure. Some Biostimulants are able to increase disease tolerance, they are not fungicides as such. Like fertilisers in the UK, Biostimulants are not registered and there is no regulatory framework attached to biostimulants, so long as there are not claims attached to the direct control of pesticidal attacks, whether fungal or insect.

Amino Acids

Turfgrass needs to produce proteins to support the process of normal cellular growth. Proteins are formed by joining together sequences of different amino acids. Many different types of proteins are needed for building cell structures and for the huge variety of enzymes required to facilitate the complex biochemical pathways of a living plant cell.

Plants have a natural ability to manufacture the amino acids needed for protein synthesis and normal growth. However, research has found that supplementing the grasses nutrition with a mixture of amino acids can be beneficial to health, especially during times of high stress caused by; high temperatures, low soil moisture, frost in winter and early spring and recovery from the aftermath of insect, nematode or disease attack. Under stress, grass is less able to absorb mineral nutrients and consequently the ability to synthesize L-amino acids is diminished. Providing turf with ready-made amino acids saves a great deal of energy, which is most beneficial when such environmental conditions are less favourable.

When applied to the soil, amino acids are an excellent food source for microbes and this will ultimately help to produce organic acids in the soil that can be utilised by the turf

Humic acids

Humic acids has been shown to have a positive impact on grass growth by increasing surface water penetration, infiltration and soil-water holding capacity. They also increase the availability of micronutrients, phosphorus and potassium.

Humic acids have been shown to retain nutrient ions, thus preventing them from leaching. They will also buffer plants from high concentrations of fertiliser salts.

Trials indicate an increase in germination rates and fibrous root development. Humic acids have also been shown to enhance chlorophyll content of leaves by increasing metabolism.

The most significant benefit is the increased ability of plants to deal with stresses such as drought, frost damage, excessive moisture and heat.

Fulvic acids

Fulvic acids help to dissolve minerals and transform them so they can be readily absorbed by grass. They are of greatest value in the plant, where they enhance nutrients, vitamins, coenzymes, auxins and metabolism which contribute significantly to plant growth and health.

Fulvic acids also promote carbohydrates and increasing levels result in the accumulation of soluble sugars in the cell, which makes the plant better able to deal with drought stress. Nutrient uptake is also improved by an increase in the permeability of the cell membrane.


Essentially, there are two types of seaweed extract available to buy in the amenity market. Firstly, there are those that have been cut and dried at high temperature, to produce a seaweed meal and later made into a liquid, before sale. These products are normally identified by their brown or black colour. This technique reduces the need for using preservative and undoubtedly lowers transport costs but although, this product still retains a lot of its minerals, unfortunately, many of the key bioactive molecules are destroyed due to the heat during the production process.

In contrast, cold extraction production (<30C) by bursting the cells of the seaweed, retains naturally occurring bioactive molecules. These include amino acids, polysaccharides, such as alginate (not heat sensitive), cellulose, laminarin, fucoidans, plant hormones, vitamins, polyphenols, fucoxanthin and chlorophyll. They either act directly as a plant bio-stimulant, as an antioxidant, influence the immune system, deter pathogens or indirectly by promoting beneficial soil bacteria.

The removal of alginates and cellulose from the formulation is a further refinement of the manufacturing process and allows for higher concentrations of the pure cell content extracted from each seaweed cell, resulting in higher concentration of the key oligosaccharides which are research proven physio activator molecules. The removal of inert materials and increasing concentration of the product also enables a reduced application rate.

Traditionally, seaweed was used to improve vigour and sward quality. Whilst more recently, cold pressed seaweed has also found a role in sports turf, for its impact on managing nematode populations. Fucoidans and oligosaccharides compounds found in seaweed mimics the microbial proteins of bacterial cell walls. The plant recognizes these in the same way it would do a mycorrhiza, as a non-pathogenic stimulus and this can increase a plant’s defence.

Seaweed is also effective for the reduction of stress levels in grass. This is thought to be achieved due to the action of hormones regulating levels of antioxidants.

Seaweed and particularly the cold pressed extract, associated with Ascophyllum nodosum, has also been shown to stimulate the increased accumulation of phytochemicals that play a role in plant growth and defence, such as phenolic and flavonoid compounds. Indeed, trial results indicate regular application of seaweed extracts can significantly increase the total phenolic and flavonoid content in specific plants, such as grass, prolonging growth during adverse weather conditions and increasing recovery rate after wear.


Biostimulants are ideally suited for use on all sport turf surfaces from Stadia to Golf. As mentioned Biostimulants are known for what they do and with a healthy sward of grass it maybe difficult to identify the positive benefits of using Biostimulants. Turf which has received regular applications of Biostimulants will perform better because they have developed a better defence system, “SAR systemic acquired resistance”. Course Managers along with all other turf managers are under constant pressure to present all year round perfection, this is not always possible. Having Biostimulants as an ingredient certainly helps relieve human and turf stress.


Most Biostimulants are in liquid form eg seaweed, humic and fulvic acids. These would be applied using a boom type sprayer which is calibrated. If they are dried/granular eg charcoal or dried seaweed either a drop spreader or rotary type should be used. When using either type of application method, the equipment should be accurately calibrated and all relevant PPE should be used.

Most Biostimulants are compatible and can be safely tank mixed, to ensure compatibility a jug test should be carried out or ask your Amenity Agronomist for advice.