How Biostimulants Support Sustainable Growth in 2025

Biostimulants are harder to define than you might expect. In fact, governments have met several times to establish a clear definition of biostimulants but there’s still no universal agreement. European countries have a different definition from Canada, and in the US, nobody has come to a full agreement on it. Despite the confusion, one thing is clear: biostimulants are transforming how cultivators approach plant health.

Unlike fertilizers that provide direct nutrients, biostimulants work by triggering natural plant processes that enhance nutrient uptake, stress tolerance, and overall growth.

As Dr. Av Singh described it, biostimulants represent the “less is more” philosophy, small, precise inputs that create a cascade of beneficial reactions within the plant.

Is It Possible to Define Biostimulants?

As discussed above, the uncertainty and difference in classification can make regulation complex. A core idea behind biostimulants is that they are not direct fertility inputs. They don’t replace fertilizers but rather complement them by activating natural biological pathways that improve plant performance. However, many biostimulants such as protein hydrolysates contain nutrients like nitrogen, making them capable of acting as fertilizers if applied in larger quantities.

The distinction often comes down to dosage and intention. At higher rates, a product may feed the plant directly; at lower rates, it acts as a signal to stimulate plant processes.

Less is More

The “less is more” concept is central to understanding how biostimulants work. They aren’t meant to provide nutrients directly but to trigger responses within the plant that lead to improved health and fertility.

For example, squid or fish hydrolysate can serve as a fertilizer when used at 10–15 milliliters per liter, but at just 2 milliliters per liter, it becomes a biostimulant. At that lower rate, it may not contribute much NPK value, but it delivers amino acids such as glutamic acid or glutamine that help open calcium channels, allowing plants to take up more calcium naturally.

This example illustrates the unique power of biostimulants: they don’t add more, they activate more.

The Major Types of Biostimulants

Today, biostimulants are used across nearly every sector of agriculture, from small-scale organic operations to large conventional farms. Some of the most common types include:

1. Humic and Fulvic Acids

Humic and fulvic acids are among the most widely used biostimulants in the world. They help chelate nutrients, making them more available for plant uptake. Humic substances can be derived from worm castings or compost but are most often extracted from leonardite or lignite using alkalization processes.

Humic acids typically have a high pH (around 8), while fulvic acids are more acidic (around 3.5). In hydroponic systems, growers often use them to adjust pH. Humic acid as a pH up and fulvic acid as a pH down, while benefiting from their nutrient-chelating properties.

2. Microbial Inoculants

Microbial biostimulants, like Trichoderma, are widely praised for their ability to promote root growth and plant health. In crops such as cannabis, Trichoderma often performs better than mycorrhizae due to shorter growth cycles and controlled environments.

3. Amino Acids and Protein Hydrolysates

Protein hydrolysates derived from sources like fish, soy, or squid enhance root mass, stem strength, and overall vigor. Their benefits depend on concentration, small amounts trigger plant responses, while higher amounts act as fertilizers.

4. Seaweed and Algal Extracts

Seaweed and algal extracts (including spirulina and chlorella) contain compounds similar to those found in marine plants, helping improve stress tolerance and plant resilience. They’re becoming increasingly popular in controlled environment agriculture.

5. Inorganic Compounds

Certain inorganic compounds, such as silica, are gaining attention as powerful biostimulants. While not classified as essential nutrients, they can significantly improve plant structure and health. Silica, in particular, is considered one of the most underrated inputs and may one day be recognized as essential.

How Biostimulants Work

Biostimulants do not act as fungicides or pesticides and cannot legally be claimed to treat biotic stress caused by pathogens or pests. Instead, they help plants cope with abiotic stress, dealing with challenges such as heat, cold, drought, or salinity.

Application Methods

Biostimulants can be applied in several ways, depending on the crop and production system:

• Seed Treatments: Algal extracts, protein hydrolysates, and humic substances are often used to enhance germination and early root development.
• Foliar Applications: Fulvic acid is particularly effective as a foliar additive due to its small molecular size, allowing it to chelate nutrients and pass through stomata efficiently.
• Soil Drench or Fertigation: Most biostimulants are incorporated into existing nutrient regimens, providing synergistic effects.
• Hydroponic Systems: Many hydroponic growers now include biostimulants to simulate the benefits of living soils and promote root zone activity.

Timing, Dosage, and Precision

Timing and dosage are critical. Overapplication can overstimulate plant immune responses, leading to stress or, in sensitive species like cannabis, hermaphroditism. Biostimulants should always be used sparingly, in alignment with the “less is more” principle.

Sustainability and Innovation

Beyond their plant benefits, many biostimulants contribute to sustainability. They’re often made from byproducts of the food and agriculture industries, like fish waste, soy meal, alfalfa meal, or even squid processing remnants. Companies like Squid Juice repurpose waste from calamari production into usable agricultural inputs.

What began as simple organic extracts has evolved into a new wave of precision inputs. Researchers and manufacturers are now isolating specific molecules and plant hormones to create targeted biostimulants for precise effects. Once considered a niche for small-scale organic growers, biostimulants are now being widely adopted by large-scale conventional producers, signaling a major shift in how agriculture views plant nutrition.

A Small Input With a Transformative Impact

Biostimulants aren’t fertilizers, but they are redefining plant nutrition. By triggering natural physiological responses rather than directly feeding nutrients, they represent a smarter, more efficient way to cultivate. Whether used to strengthen roots, improve stress tolerance, or enhance nutrient uptake, biostimulants are becoming an essential tool for growers everywhere.

Want to Learn More About Biostimulants?

Watch our webinar “Root to Canopy” with Dr. Av Singh!

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