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Adding Biostimulants to Plants

If you’re aiming to grow healthy plants, you might want to consider adding biostimulants to your growing routine. You might know that you need to supply your plants with required nutrients. However, you might not know that plants might not be fully utilize these nutrients.

Biostimulants are a category of substances that work to increase nutrient uptake and use in plants. They also improve plant quality and stress tolerance to weather, pests, and diseases.

People call biostimulants by other names including plant conditioners, bioactivators, and bio enhancers. They consist a range of substances including:

  • humic acids
  • microbial inoculants
  • fulvic acids
  • seaweed extracts

As research around these substances grows, more products are becoming available to growers. You can apply these substances in their raw form or as a component of a fertilizer mixture. They’re effective at various points of plant growth, from seeds to mature plants. Continue reading to learn more about each of these materials.

Definition of Biostimulants

There is no legal definition or regulation of biostimulants. Perhaps because they include such a wide variety of substances and products. Therefore, consumers are often confused about what biostimulants are.

People are beginning the process to regulate these products and this market. Due to public pressure, the 2018 US farm bill included the definition as “substance or microorganism that, when applied to seeds, plants, or the rhizosphere, stimulates natural processes to enhance or benefit nutrient uptake, nutrient efficiency, tolerance to abiotic stress, or crop quality and yield.”

Along with this definition, people generally accept that all of these products are naturally derived. They consist of materials such as seaweed, acids derived from decomposed organic matter, and bacteria.

So, what does this mean? You should research the composition of products before you buy. If manufacturers make claims about their product, make sure the listed ingredients support these claims. Not sure of the benefits of different substances? Continue reading to learn more.

Benefits of Biostimulants

If you break apart the name, biostimulant literally means stimulant life. These substances do just that via a variety of means. People only partially understand the impact these materials have on plants. Researchers are still working to understand exactly how these materials cause these impacts.

While the group of materials considered biostimulants is diverse, they do share a few common characteristics. All of these substances benefit plants by stimulating processes that:

  • increase nutrient uptake
  • improve stress response
  • improve plant quality

The key point is that biostimulants do not necessarily provide nutrients; they are not fertilizers. Also, they do not directly impact pests and diseases; they are not pesticides. Instead, they improve plant health through a variety of ways. This is why people often refer to them as plant enhancers.

These materials provide a diversity of benefits. They have the ability to increase the growth of lateral roots. This allows plants to better locate and take up nutrients in the growing media. They can increase a plant’s ability to take up water, which makes it easier to provide successful watering practices. These substances can also help plants resist stresses including drought, low temperatures, diseases, and insect pests.

Drawbacks of Biostimulants

Scientists have conducted some research regarding the impact of these substances on plants. However, people don’t fully understand their role in plant health.

You can look at or test a plant and say it is deficient in a nutrient, and then apply said nutrient to help with this problem. Biostimulants do not address these specific problems but rather serve as whole plant conditioners.

Some biostimulants are living products, so they have expiration dates. You also must monitor storage conditions to prevent products from going bad.

Humic Acid

Humic acids are dark brown substances derived from organic material. The base of humic acids is decomposed organic matter such as peat, coal, and leonardite. These substances undergo a process to extract the bound humic acids. Humic acids are insoluble in strong acids.

When you add humic acid to soil, you increase the cation exchange ratio, or CEC. The cation exchange capacity is a measure of how many cations – positively charged ions – a soil can hold. The more negatively charged sites a soil contains, the higher its CEC.

Growers can increase the CEC of their soils by adding clay, organic matter, and substances such as humic acids. These substances contain negatively charged sites that bind to and hold cations.

A higher CEC is favorable as this means the soil can hold more cations. Therefore, more cations are available to plants. Some cations important to plant growth are calcium, magnesium, and potassium.

Another major benefit of humic acids is their ability to chelate plant micronutrients including copper, iron, manganese, and zinc. Chelation is a process where metallic ions bind to organic compounds such as humic acid. This prevents these ions from leaching out of the soil and into the surrounding environment.

Research shows humic acids increase plant root growth. This allows plants to reach out into the soil for water and nutrients.

Applying Humic Acids

All of the previously mentioned benefits allow you to apply fewer nutrients. This helps you save money and prevents environmental contamination. Perhaps most importantly, humic acids help plants obtain nutrients needed to perform the vital functions.

Growers can add humic acids to soil or other growing media in a variety of ways. Humic acids are available in liquid and solid form. People often call the solid form humates. Many humic acid products are sourced from naturally occurring leonardite. These products are available in their pure form, or as mixtures with other biostimulants and nutrients.

Microbial Inoculants

You may have heard that living soil is healthy soil. It’s true! Soil is not just crushed up rocks and nutrient components. It’s full of life! It is teeming with bacteria, fungi, protozoa, and other forms of life.  In fact, one teaspoon of soil contains between 100 million and one billion bacteria!

Microbial inoculants provide your soils with a dose of these beneficial lifeforms. These substances come in a variety of forms. They contain a variety of species that provide diverse benefits to both plants and soils.

Beneficial Bacteria

One main type of microbial inoculants are beneficial bacteria. Healthy soil contains millions to billions of bacteria made up of many different species. These bacteria consist of various types and shapes, and they provide diverse benefits to soil and plants. Fortunately, you can add some of the species to your plants in the form of inoculants.

One type of bacteria, Rhizobium, helps legumes (peas, beans, vetch, etc.) fix nitrogen from the atmosphere. Each species of plant has a specific species of rhizobacteria that live on the plant’s root nodules. In order to ensure these plants are able to fix nitrogen, seeds are often dusted with a microbial inoculant.

Other types of beneficial bacteria often found in microbial inoculants include those found in the genus Azospirillum, Bacillus, and Pseudomonas. Some of these bacteria protect plants against diseases and pests while increasing plant growth and yield. These bacteria accomplish this in a variety of ways including by encouraging the creation of plant hormones. However, it is important to note that they do not affect pests directly. Instead, they improve a plant’s response to pests.

Bacteria also improve the soil. They hold together soil particles to form small clumps of soil called aggregates. These aggregates improve soil structure, and water can better infiltrate and permeate.

Bacteria also work to decompose organic matter in the soil. They are crucial to composting operations, and also help break down residues from weeds and previous crops.

Fungal Inoculants

Fungi are another type of organism found in microbial inoculants. Just as with bacteria and plants, there are thousands of species of fungi. While some are plant diseases, others are key to helping plants grow.

The majority of plants form symbiotic relationships with mycorrhizal fungi. In fact, around 90% of plants have some kind of relationship with mycorrhizal fungi.

These fungi attach onto the plant roots and then grow out into the surrounding area. This acts like an extended root system for the plants. Therefore, plants can obtain more nutrients and water than they would be able to on their own.

Not only do microbial inoculants contain different species of microorganisms, but they also exist in a variety of forms. Some products are powders, such as seed inoculants. Others are liquids that growers dilute then spray on growing crops.

Focusing on microbial inoculants and soil biology, instead of chemical inputs, is a way of growing sometimes known as microbe organics. There is a large focus on the understanding of biology, biochemistry, and ecology.


Microbe Organics

People that grow plants with a focus on microbial life are sometimes said to be following principles of microbe organics. Not only are growers using organic methods, but they are also focusing on creating living soils.

Fulvic Acids

While fulvic acids are similar to humic acids in some ways, they are different classes of biostimulants.

Fulvic acids are smaller than humic acids. Also, they’re soluble at lower pH levels than humic acids. They are lighter in color than humic acids, and have a yellow to yellowish-brown color. Products containing fulvic acids are typically lower in pH (more acidic) than those containing humic acids.

Since fulvic acids are so much smaller than humic acids, they can help plants absorb nutrients directly.  Just like humic acids, fulvic acids can take hold of certain nutrients via chelation. Once these nutrients are bound, the fulvic acids enter the plant and deliver the nutrient. Fulvic acids are small enough to enter through the plant’s stomata, so they work well as foliar sprays.

Fulvic acids are available in their pure form, as well as mixed with other substances. It often makes sense to apply fulvic acids with micronutrients such as copper, zinc, and iron, as they will be held via chelation.

Seaweed Extracts

Seaweed extracts are liquids made from various types of seaweed. Not all seaweed extracts are equal, as they are made from various species of seaweed and via different processes. Some processing methods include fermentation, cold pressing, and alkaline hydrolysis.

Extracts contain a variety of beneficial substances. Analysis shows that they contain a variety of plant growth regulators including cytokinins, gibberellins, and abscisic acid.

Cytokinins encourage the division of cells in plants as well as impact senescence in plants. Gibberellins speed up seed germination and increase cell division. Abscisic acid helps with the closing of the stomata. Therefore, it helps plants respond to heat and drought.

Seaweed extracts also contain trace minerals that provide plants with nutrients that are often lacking.

It’s not fully understood how each of these elements of seaweed extracts directly affect plants. However, people know that seaweed extracts impact plants. Studies show that hundreds of plant genes respond when seaweed extracts are applied. Consequently, plants show positive responses.

Seaweed extracts help promote plant root development and growth. When growers apply seaweed extract to seeds or growing seedlings, transplants display increased root vigor. With these stronger roots, plants can better reach and absorb water and nutrients. Seaweed also improves plant tolerance to intense heat as well as frost.

Seaweed extracts not only improve plant growth, but they also improve soil conditions. They improve soil structure and encourage populations of beneficial microorganisms. Both of these increase plant growth.

Growers can these extracts to seeds, root cuttings, transplants, and fully grown plants. Applications methods include foliar sprays, soil drenches, or hydroponic solutions.

Wrapping Up

By now you know that the term biostimulant covers a wide variety of substances and products. All of these substances enhance plant growth. They include humic acids, fulvic acids, seaweed extracts, and microbial inoculants. These substances can play a vital part in growing healthy plants, along with applying nutrients and providing the right growing conditions. However, make sure to read the product labels, so you know what you are getting for your money.

We are continually learning more about biostimulants and their benefits, so read up on the latest research to keep up to date. However, from what we currently know, biostimulants will benefit your plants

Categorized as Nutrients

By Briana Yablonski

Briana grew up in Eastern Pennsylvania and currently resides in Knoxville, Tennessee. She holds a Bachelor of Science in plant sciences from Penn State University and has worked on produce farms in Minnesota, Pennsylvania, Virginia, and Tennessee. She now runs her own small farm and enjoys walking dogs at the local shelter, hiking, and riding her bike.