Humic and fulvic acids are two different organic compounds derived from decomposing organic matter, such as fallen leaves, compost, and other plant materials. While both have the same origins, humic acid is a much larger molecule and has a few differences from fulvic acid in how it benefits turfgrass and your soil’s microbiome. Today, I’ll compare humic vs fulvic acid to help beginners understand how each can help to improve your lawn by improving the soil it grows in.
This article was last updated on by Lawn Chick Owner Sarah Jameson
Article content reviewed for accuracy by Horticulturist Arthur Davidson, A.S.
One of the main differences between the two acids is how they act. Because humic acid is more complex, it takes longer to break down. Fulvic acid is still essential for soil health, but it breaks down quickly and is best used during the growing season.
When applied to your lawn or garden, both humic and fulvic acid help to improve soil quality by providing (and making accessible) essential nutrients like nitrogen and phosphorus, which help plants grow.
- Humic acid helps promote root growth, water retention, and nutrient availability, while
- Fulvic acid helps to quickly break down nutrients and make them more readily available for plants.
Best Overall Lawn Soil Test Kit
The Soil Test Kit I Use & Recommend
There are many options for testing your lawn’s soil, but I prefer a lab-based soil test that provides a detailed analysis of your soil’s nutrients and what’s needed for your lawn to thrive.
I use this one from MySoil every year.
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Introduction to Humic and Fulvic Acids
Soil is a very complex ecosystem that is made up of a variety of organic and inorganic components. Humic and fulvic acid are two important organic components that are essential in maintaining soil health.
Absorption of nutrients into your lawn can be limited by soil pH and the presence of organic matter. Humic and fulvic acids provide chelating agents to help neutralize soil pH as well as essential nutrients like phosphorus, potassium, magnesium, calcium, sulfur, iron, and zinc.
Humic acid is an important component in organically rich soils due to its ability to bind with minerals and improve water retention in the soil. It is derived from decomposed plant material, including leaves, grasses, and woody material.
Humic acid is usually composed of humates, humic acids (which provide the cation exchange capacity), and fulvic acids.
Fulvic acid has a much smaller molecular weight than humic acid and is more water-soluble.
As I mentioned the cation exchange capacity (CEC) earlier, I should explain exactly what that is. The CEC is your soil’s capacity to retain cations and exchange them.
But what is a cation? Well, it’s a positively charged ion. Examples include potassium, magnesium, and calcium ions. When soil can hold on to these nutrients, that makes them accessible to your plants longer, and your lawn can use them as they’re needed.
Essentially, this stretches your dollar and helps your lawn utilize more of the fertilizer you spread.
But, let’s get back to the sources and benefits of humic and fulvic acid. Knowing about this can help you choose the best soil amendment for your needs.
Sources and Benefits of Humic Acid
The formation of humic acid is quite complex and is dependent on a variety of factors.
The main ingredients that are needed for humic acid production are organic materials, such as decomposing plant matter and bacteria.
Humic acids have numerous benefits for soil. They
- create better soil structure,
- increase water retention, and
- facilitate better nutrient uptake and availability.
Also, they encourage increased microbial activity, as well as higher cation exchange capacity.
Humic acid is manufactured and sold as a soil amendment. It is formed when microorganisms like bacteria break down certain kinds of organic matter, such as decomposing plants.
Creating humic acid is a more complex process than producing fulvic acid. That is why it is a bit more expensive. You can browse some of my favorite humic acid products right here.
Sources and Benefits of Fulvic Acid
It is important to understand that humic and fulvic acid have different sources, chemical compositions, and properties. That makes them unique in terms of their uses and the benefits they provide.
Fulvic acid sourcing has similarities to humic acid. However, it’s slightly different in that it’s derived from humified organic matter such as peat and compost.
Microorganisms produce fulvic acid when they break down organic material.
It is much more water soluble than humic acid. That is because it has a smaller molecular weight that makes it easier for plants to absorb and benefit from.
Fulvic acid offers soil a number of benefits. These include:
- increased cation exchange capacity,
- improved nutrient availability,
- better water retention, and
- improved soil structure.
Often, you’ll find humic and fulvic acid products offered pre-mixed in combination in many liquid fertilizers applied with a hose-end sprayer.
Differences Between Humic and Fulvic Acids
Despite the similar origins of the two acids, there are quite a few differences between humic and fulvic acid.
The most important difference is their molecular weight, with humic acid having a much larger molecular weight than fulvic acid.
This higher molecular weight makes humic acid less water soluble than fulvic acid. That is why it’s a bit more difficult for plants to absorb.
Humic acid has a higher molecular weight because of its molecule size and structure.
While humic acid is comprised of both carbon and nitrogen, fulvic acid contains mainly carbon but no nitrogen.
The presence of nitrogen in humic acid is what gives it its chelating properties. It’s effective at binding to minerals and providing them to plants.
In terms of their benefits to the soil:
- Humic acid is better at improving water retention and cation exchange capacity.
- Fulvic acid is more efficient at providing minerals and nutrients to plants. That is because of the shape of the molecule and its retention properties.
The Role Organic Matter Plays in Replenishing Soils
Lawn health is a complex and delicate balance of nutrients, minerals, soil structure, and organic matter.
According to Arthur Davidson, a horticulturist with over five decades of experience (and a member of Lawn Chick’s expert panel), “the soil is the ‘life blood’ of all plants. I am a huge proponent of the use of mychorrizal fungus and beneficial bacteria.” He adds that “both humic and fulvic would be beneficial to maintain and improve the lawn.”
Organic matter plays an important role in replenishing soils by providing beneficial microbes, improving soil structure, and providing nutrients that are readily available for plants to absorb.
Before microbial activity developed on our planet, trees piled up without any composting or decay, leading to the formation of coal and petroleum over very long periods of time.
Organic matter serves as a food source for soil microbes, providing them with energy for metabolism and growth. These beneficial bacteria then release essential nutrients back into the soil, which plants can absorb.
This cycle is what makes organic matter so important in replenishing soils. It helps provide nutrients and minerals to plants while also helping to improve soil structure.
Humic acid and fulvic acid are two important organic molecules that can help in this process. Both acids can be found naturally in soils or manufactured for use as a soil amendment, with each of them providing different benefits for lawns and gardens.
How Humic Acid Improves Soil Structure
Humic acid is an incredible compound as it has the ability to improve soil structure and increase water retention.
It acts as a chelating agent, binding to minerals and making them more available for plant absorption. It also helps reduce compaction in soils, allowing root systems to grow deeper into the ground and access more nutrients.
Humic acid is created by microbial activity, which breaks down dead organic matter into pieces small enough to be absorbed by plants. The acid helps bind these pieces together, making them easier for roots to access.
It also helps prevent erosion and can even reduce the leaching of nutrients from the soil, allowing them to remain in the root zone where they are more readily available for plants.
Humic acid also helps aerate soils and increase the cation exchange capacity, allowing for more nutrient uptake by your lawn and other plants. While it isn’t as complex, fulvic acid plays a very important and similar role in the uptake of nutrients.
How Fulvic Acid Improves Plant Uptake of Nutrients
Fulvic acid is very different from humic acid in terms of molecular structure and how it works.
It has a much smaller molecular weight than humic acid, making it more easily absorbed by plant roots. This small size allows fulvic acid to carry essential nutrients and minerals directly into the cells of plants, providing them with an instant dose of nutrition.
Fulvic acid is also a powerful chelator, meaning it binds to minerals in the soil and helps make them available to plants. By binding to minerals in the soil, fulvic acid can help protect against nutrient loss due to leaching or runoff.
The fulvic acid molecule is also capable of transferring electrons between molecules, giving it the ability to help stimulate metabolic reactions in plants and animals. This helps promote healthier plant growth, resulting in larger yields with more nutrients.
The production of fulvic acid is also much easier than humic acid, as fulvic acid is derived from organic materials that are broken down by bacteria and other microorganisms. As these organic materials decompose, fulvic acid molecules are released.
Fulvic acid’s ultimate benefit is how it provides plants with an immediate boost of nutrition, helping them take in more nutrients from the soil and grow healthier and stronger.
When used regularly on lawns and gardens, it can also help improve soil structure and fertility over time.
Make sure you understand the differences between humic acid and fulvic acid so that you can make an informed decision about which one is right for your lawn or garden.
Each has its benefits and drawbacks, so understanding how they work will help you decide if one product fits your needs better than the other.
Which One is Better for Your Lawn? Humic vs Fulvic Acid
Deciding which product to use on your lawn or garden is an important decision. Humic acid and fulvic acid provide their own unique benefits.
Your Lawn Will Benefit From Humic Acid if…
Humic acid helps improve soil structure by binding particles together, and you can use it over extended periods of time. As it gradually breaks down, it releases minerals into the soil. This helps to build healthy soils that are rich in nutrients.
You should choose to apply humic acid to your lawn if retaining moisture is difficult for your grass. Humic acid is fantastic for helping the roots of your grass. It also helps other plants retain moisture, helping them stay hydrated and healthy.
Your Lawn Will Benefit from Fulvic Acid if…
On the other hand, fulvic acid is best used to give your plants a good shot at nutrition. Its small size makes it highly absorbable by plant cells.
So, it provides an instant boost of minerals that can help stimulate metabolic processes and promote healthy growth.
Because of the shape of fulvic acid, the pores of the soil remain open and free, allowing water and air to penetrate them. This helps keep your soil in good condition without compromising nutritional uptake.
Many Homeowners have Lawns That will Benefit from Both
If you feel that both of these would be suitable choices for your lawn, nearly all humic acid products contain a certain amount of fulvic acids. This gives you the chance to benefit from both products at the same time.
You can save money if you’re sure that you don’t need humic acid and only want fulvic acid. In the event that you want some extra moisture retention and also want the benefits of fulvic acid, it’s best to go for a product with a good balance of both.
How to Apply Them Correctly on Your Lawns
Both fulvic and humic acids come primarily in liquid form and should be applied directly to the soil.
One of the most common ways of applying fulvic and humic acids are with sprayers or hose-end applicators.
Experts say that you should conduct a soil test before you use either of these acids and/or other amendments, such as lime or gypsum.
Every year I aerate my soil, and for me, this is an ideal time to apply fulvic and/or humic acid. That way, it can penetrate the soil and get down to the grass roots more easily.
In my experience, this is especially beneficial when applying humic acid, as it helps break down soil particles and improves water infiltration.
While fulvic acid is nearly always in liquid form, you can also find humic acid in granular or powder form.
If you’re using granular humic acid, you should use a good fertilizer spreader to apply it. This will ensure that you’ll get even coverage all over your lawn.
How often you should apply either of these products will depend on the product itself and your own specific soil requirements.
Generally, experts say you should apply humic acid once a season, while you can apply fulvic acid more frequently and enjoy excellent results.
Final Thoughts on Humic vs Fulvic Acid for Lawns
I highly recommend using a combination of both humic and fulvic acids to get the best results for your lawn, especially if moisture retention is your biggest issue.
Many of the products I recommend as part of my free lawn care cheat sheet (which offers a ready-to-use lawn fertilizer schedule for the entire season) include applications of these soil-builders.
A product with a good balance of humic and fulvic acid will help you nourish, protect, and improve the structure of your soil while improving water retention, nutrient uptake, and overall plant growth.
Again, check out this page for a list of some of my favorite lawn products with humic and/or fulvic acid.
At Lawn Chick, I am committed to publishing accurate, useful, and trustworthy resources for my readers. As part of this commitment, I’ve invited subject matter experts to review our articles for accuracy. I invite you to read our editorial policy and publishing standards which outlines in detail how every article on this site is sourced, edited, fact-checked, and vetted.
-Sarah
