What is Humic Acid? [and How To Use It]

What exactly is humic acid? Do I need it on my soil? How will it benefit my soil and plants? It can be confusing with varying opinions out there and we will try to clear that up.

Humic acid is a naturally occurring substance that can be found in soil and other environments. It is among one of the compounds generated in the soil after humus decays. It has three uses: 1) as a fertilizer complement, 2) to improve soil texture, and 3) to maintain healthy lawns.

To comprehend how humic acids form, it is necessary to first discuss soil composition and the formation of humus.

The 3 Uses of Humic Acid

Soil is composed roughly of 45% minerals, 25% air, 25% water, 2% non-living organic matter, 2% humus, and 1% living organisms (bacteria, fungi, and insects).

Humification or the formation of humus is a continuous cycle that starts with the breakdown of organic matter (always present in typical outdoor soil) by decomposers in the soil and at the same time, the disintegration of rocks due to weathering and organisms. After that, the result is the formation of a compound called humus.

Humus breaks down further into 3 molecules which are collectively called humates. Humates are composed of humic acid, fulvic acid, and humin. At this stage, no further decay happens and humic acids start to interact with plant roots.

Humic Acid Uses – Infographic

Use #1 – Fertilizer Complement

Due to the number of soil supplements out there, many often confuse humic acid as fertilizer.

Humic acid is not a fertilizer and consequently, it is not a direct source of plant nutrition. Humic acid is used in conjunction with both organic and synthetic fertilizer as a soil conditioner.

This is despite the fact that you can sometimes find humic acid as a standalone product (and cause confusion).

How Does Humic Acid Work in Plants?

Humic acid is a source of carbon and phosphate that is consumed by beneficial fungi and bacteria that encourages these organisms to release minerals such as magnesium, calcium, and iron into the soil. The positively charged minerals are attracted to and bound by the negatively charged humic acid ions.

The humic acid molecule goes closer to the roots’ higher negative charge, carrying minerals and water with it. The minerals will separate from the acid and travel to the root of the plant, where they will be absorbed for sustenance.

The phenomenon described above is called “Cation Exchange Capacity.” Many nutrients will remain locked in the soil without it.

Higher plant nutrient intake results in: a) improved root development, b) better seed germination rate, c) increased photosynthesis, d) bumper crop harvest and e) enhanced water uptake.

What Is the pH Of Humic Acid?

The humic acid has a pH level between 8 and 9. This is a basic substance.

In the context of soil and growing plants, most people look at humates, not from the scientific viewpoint but as commercial products. To manufacture humate products, a lump of very soft coal called leonardite is ground, pelletized, or powdered and packaged into granular products.

To produce humic acid products in liquid form that is water-soluble, leonardite ore is subjected to liquid extraction and reduction processes. The resulting liquid which has a pH level of 8 – 9 is what is commercially sold as “humic acid.”

How Is Humic Acid Used In Agriculture?

Humic acid is used in agriculture not as a fertilizer but rather as a complement to soil and foliar fertilizer.

Several people believe it is a component of many “all-in-one” fertilizers. Unfortunately, it’s usually offered as a separate item or with one type of fertilizer added such as Nitrogen. This acid is used as a complement to foliar fertilizers.

Benefits to Agriculture

  1. Better yield due to increased transport of nutrients from the soil to the roots.
  2. It makes cultivation easier because with better soils the constant addition of fertilizer will be reduced.
  3. Better drought tolerance and prevents wilting of crops.
  4. Increased cell wall permeability enabling nutrients from foliar application to easily enter the plant.
  5. Lowered the toxicity of metal concentrations in the soil into non-toxic levels.

Research shows that potatoes planted on calcareous soil treated with Phosphorus responded well and yielded better quality crops after the addition of humic acid.

Use #2 – Improve Soil Texture

Soil texture describes the proportion of mineral particles present in soil and whether the soil is coarse or fine. The mineral matter in soil is composed of various combinations of sand, silt, and clay particles.

Does Humic Acid Improve Soil?

Humic acid is shown to improve these soil characteristics:

a) Water-holding capacity which refers to water retention of the soil,

b) Water infiltration, which refers to whether air and water can infiltrate the soil effectively, and

c) Soil workability refers to whether it’s easy to cultivate the soil.

The Effect Of Humic Acid To Sandy Soil

Because it is the largest mineral particle, it has a rough texture. Soils with a high sand content are generally well-draining, but they can be difficult to work with since nutrients are carried away from the root.

Humic acid slows down water evaporation on sandy soil at a rate of 30% thereby increasing its water-holding capacity.

The Effect Of Humic Acid To Clay Soil

Because it is the largest mineral particle, it has a rough texture. Soils with a high sand content are generally well-draining, but they can be difficult to work with since nutrients are carried away from the root.

Excessive fertilizing causes salt deposits in clay soil, which in the worst-case scenario leads to heavily compacted soil. Humic acid helps to break up compressed soil by isolating and separating those salts from clay leading to better water permeability and well-draining soil.

Use #3 – Lawn Care

Does Humic Acid Really work for Lawns? | 2 Year Humic Acid Results

Opinions on the usefulness of humic acid on lawns vary among homeowners is controversial and not clear:

  • Some say that it is a waste of time and money when your soil and lawn is already healthy because you will not notice any difference anyway.
  • Others who have used it as a soil drench and as powder spread on their lawn and vegetables can only comment about the bumper crop harvest but not on their lawn.
  • Still, there are those who say that the acid solved their hydrophobic soil issues by allowing water to permeate through the grass into the soil.
  • Even golf courses, where the importance of a good lawn is paramount for their own business, do not use humic acid everywhere but just in the most important area of the field ignoring pathways and other less prime areas. I suggest you do the same with your own lawn!

A friend of mine who used it on his Bermuda grass noticed that two days after application, the lawn turned into a deep green shade. This can be attributed to Nitrogen (N) in the soil being more accessible to the grass.

When soil compaction is a problem in your lawn, apply humic acid before reseeding. The acid will help soften the compacted soil. Indeed those who have used it successfully on their turf continue to do so as part of their long-term lawn care schedule.

Can You Put Too Much Humic Acid On Soil And Lawn?

Since humic acid is not a fertilizer, by itself, it will not burn your soil or lawn. Some manufacturers add N to their humic acid formulation. Adding N is not bad by itself however, if you’re not aware of it, you could end up adding too much humic acid to your turf and end with damaged soil and grass.

When Is The Best Time To Apply Humic Acid To Lawns?

The best time to apply humic acid is during the reseeding season in the spring or fall. It should be applied after spreading fertilizer. Water-soluble humic acid should be applied at a time in the day when there is less chance for the liquid to evaporate.

Apply it to your lawn up to twice a year in the spring and fall. You do not have to water in liquid humic acid because it could get washed out. When you use the granular kind, you need to water it so that the pellets can break down.

Humic Acid In Water

Humic acid also exists in fresh and saltwater systems. Together with fulvic acid, they represent roughly 50-75% of the total dissolved organic matter in the water. Scientists have not yet discovered how humates formed in water systems but the theory is that it came from decomposed water organisms and from plants and soil.

Here are some theories regarding how humate compounds function in aquatic systems:

  • Because of their capacity to bind heavy metals, they can reduce their detrimental effects on water.
  • Reduce the growth of algae in bodies of water.
  • Form compounds that are eaten by zooplankton.
  • It helps aquatic organisms in developing and surviving in harsh situations.
  • It is able to replace the typical food chain in lakes rich in humic acid with a detritus food chain which can produce more bacteria.

Where Do You Find Humic Acid?

As previously noted, leonardite ore is used to make commercially available humic acid. One of the first leonardite deposits was discovered in Dakota, and another was discovered in New Mexico.

A humus-rich soil sample, peat moss, peat bogs, and humic compost can all be used to extract humic acid. It is possible to extract it yourself from humic compost, but it is a complex process that requires knowledge of chemistry, specialized equipment such as a centrifuge, and chemicals such as potassium hydroxide.

Where Humic Acid Can Be Bought?

There are many places where you can acquire commercial humic acid. You can find this in garden centers, agriculture supplies shops, and independent sellers online. There’s also plenty of it being sold on Amazon such as this product.


  1. Humic acid is everywhere where the breakdown of organic matter happens.
  2. Although it’s benefits to soil are well established, there aren’t yet enough studies concerning humates in other geologic systems apart from soils.
  3. It is possible to extract it yourself from your own compost-rich soil if you have a small laboratory setup.

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“Humic Acid” by n.a. In THCtalk

“Soil Texture and Structure” by n.a. In CAERT

“Humic Acid: The Crucial Component Absent in Most Fertilizer” by Julian Smith Phd in Johnny Appleseed Organic

“Humic Acid and Returning Soil To A Healthy State” by n.a. in Soil Biotics

“The Top 5 Benefits of Humic Acid” by n.a. Earthgreen Products Inc

“Research and Benefits of Humic Acid” by n.a. In Lawn Care Academy

“Humic Substances in Aquatic Ecosystems: A Review” by Arti Sharma in ResearchGate

“Humic Materials for Agriculture” by R.L. Mikkelsen in University of California

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