Biostimulants

What benefits do biostimulants bring to plants?

The primary role of a biostimulant should not be fertilisation or pesticide action. They are not classified as fertilisers, nor do they have a direct effect on pests. Their fundamental task is to stimulate vital processes, increase plants’ resistance to stressful conditions, and accelerate root and leaf development. Biostimulants strengthen plants’ natural defence mechanisms, enabling them to better withstand abiotic stress associated with drought, temperature fluctuations, soil salinity or frost damage. Biostimulants are therefore used to improve the biochemical, morphological and physiological processes occurring in crops.

The rise in popularity of biostimulants

Plant biostimulants are a relatively new but rapidly growing group of products in agriculture, whose popularity is rising alongside the need for more sustainable production. Increasing climate pressure and environmental degradation are prompting producers to turn to solutions based on natural ingredients. Biostimulants fit into this trend, supporting eco-friendly practices and responding to EU regulations promoting environmentally friendly agriculture.

The growing importance of biostimulants also stems from the fact that they are an effective tool for improving plant growth and yield with minimal impact on the soil. In difficult conditions, where traditional mineral fertilisation does not always ensure that plants make full use of nutrients, biostimulants increase the efficiency of nutrient uptake and can reduce the need for high doses of fertilisers. By supporting plant metabolism and improving their natural resistance to fungal and bacterial diseases, they also help to reduce the number of treatments or the dose of plant protection products, which are usually applied without the use of biostimulants. This makes them particularly valuable in intensive production systems, where the pressure to reduce chemical use is greatest. It is increasingly emphasised that biostimulants will play a key role in the sustainable intensification of agriculture, and their synergistic action with mineral fertilisers may significantly change farming practices in the future.

There are many groups of biostimulants. The most important are:

• Amino acid-based,
• Derived from marine algae,
• Containing humic acids,
• Bacterial and fungal-based.

Raw materials in the production of plant biostimulants

The raw materials used in the production of plant biostimulants are extremely diverse, as this category encompasses a wide range of substances of natural and microbiological origin.

Biostimulants can be obtained from a wide range of raw materials, including:

• Plant extracts: from leaves, roots and/or seeds, including aloe, moringa and alfalfa,
• Algae: brown algae (e.g. Ascophyllum nodosum, Laminaria digitata) and red algae (e.g. Kappaphycus alvarezii, Porphyra spp.),
• Microbial inoculants: bacteria, fungi and other microorganisms,
• Humic substances: humic and fulvic acids derived from decomposed organic matter,
• Amino acids and proteins: from plant or animal sources,
• Compost: organic and vermicompost.

In order for the active ingredients contained in biostimulants to fulfil their functions, it is essential to include adjuvants in the formulation.

The role of excipients in biostimulants

Natural plant biostimulants play a key role in sustainable plant production. In addition to the basic active ingredients, excipients are also essential in the formulation. They determine the effectiveness, stability, ease of application and miscibility of the biostimulant in the spray mixture.

The most important group of chemical compounds used to create formulations of plant biostimulants are surface-active substances – also known as surfactants. These are molecules with an amphiphilic chemical structure, i.e. they possess both a hydrophilic and a hydrophobic group, thanks to which they exhibit affinity for both polar and non-polar phases simultaneously.

Surfactants in biostimulants perform a number of important functions:

• When added to the base solution, they lower the surface tension, reducing the barrier between one liquid and another liquid or a solid. This directly contributes to more effective distribution of the preparation on the plant (spreading aids), which translates into more efficient absorption and higher bioavailability, as well as preventing the spray droplets from bouncing off and running off the leaves (retention aids).
• In suspension formulations of microorganism-based biostimulants, they improve the homogeneity of the mixture through better dispersion of the components.
• They act as emulsifiers by combining immiscible components, e.g. insoluble plant oil fractions with water. They prevent phase separation in the formulation and control its viscosity.
• They enhance the biological efficacy of plant biostimulants.

In biostimulants, it is advisable to use surfactants from the wetting agent group, such as ROKAnole L5P5 and NL8. Particularly valued among these are surfactants of natural origin – the ROKAnole L, K and O series. Their action is complemented by the use of humectants (POLIkole) and penetrants (e.g. ROKAcety R11, R26). This enables effective coverage of the leaves with the spray, moisture retention and penetration of the formulation’s components through the cuticle. Such synergistic action increases the likelihood that as many of the active ingredients contained in the biostimulants as possible will reach the tissues of the sprayed plant.

Betaines (ROKAmines) may prove to be beneficial components of biostimulator formulations. They act not only as adjuvants but also as active ingredients. Compounds from the betaine group act osmotically, regulating water transport in plant cells and increasing their resistance to stress caused by drought, extreme temperatures or salinity. They also support the process of photosynthesis, which can lead to increased agricultural production and crop quality.