How to Use Soil Amendments - Humates, Humic Acids and Humus

humate soil conditioner

Humates, humic acids, humus… these soil amendments sound so similar! They are all good for the garden even though they are not really a fertilizer (since they do not add any nutrients to the plants), and they are not all the same. Let’s look at what they are, and how to choose the best one for your needs.

What is humus?

All fertile soil contains several components: decomposing organic matter, living organisms including plant roots, microbes, worms, insects, and small animals; and humus – the carbon-rich matrix made of fully decomposed organic matter.
  • Found in any soil containing decomposed organic matter, as well as in compost, worm castings, sphagnum peat moss, and other aged organic matter.
  • The older and darker in color that it is, the more humus it contains.
  • Made up of lignins, fats, and sugars, as well as three types of chemical compounds called “humic substances”: humin, humic acids, and fulvic acids. These are each a class of chemicals comprised of many different biologically active compounds.
    • Humin is very stable, improving soil structure but not easily used by plant roots.
    • Fulvic acids, on the other hand, are the most bio-available of these chemicals but have little effect on improving the soil.
    • Humic acids can be applied to your soil to provide the most benefits over time, improving both the soil and the plants growing in it. Humic acids work to raise the Cation Exchange Capacity, or CEC, of your soil, which is important for increasing nutrient and water retention and uptake, as well as improving the soil structure. In field studies, plants grown with humic acids are bigger and have stronger roots. Even though they are called acids, they will not make your soil acidic and can be used in any type of soil, and for all your veggies, flowers, trees, and lawn.

So Where do Humates Come into This Equation?

Humic acids are naturally a liquid. Humates, also called granular humic acids (Activate 80), are what you get when humic acids are rendered into a solid, through what is essentially a dehydration process. Humates contain the same compounds and thus have the same benefits as applying liquid humic acids such as Humax. Once applied to the soil and watered in, they will dissolve into their active liquid form again. The best way to add humic acids to your soil is with humates derived from leonardite shale. Leonardite is a rock formed from pressurized peat, which has a very high humic acid content–45 to 50%! Humax, which is also derived from leonardite, is a faster acting humic acid source, but has been diluted to 12% humic acids. It is best for foliar and fertigation applications.

Adding Humic Acid to the Garden-Forms

  • Granular Humic Acids–Derived from Leonardite shale, contains 50% humic acids. Similar to Activate 80-Course, but in a smaller size.
  • Acivate 80-Course Grade Humate–Derived from Leonardite shale, contains 45% humic acids.
  • Activate 80 Micronized Humate–Derived from Leonardite shale, contains 55% humic acids. Can be delivered through irrigation lines. Does not fully go into solution, must keep agitated.
  • Humax–Derived from Leonardite shale, contains 12% humic acids. Liquid humic acid, fully water soluble.

Application of Humate

To get the benefits of humic acids in your garden, only a little humate is required.
  • Use 1 to 2 pounds per 100 square feet of garden, or 3 to 10 pounds per 1000 square feet of lawn. Top dress or mix into the root zone, and water well.
  • For potted plants, use 2 Tablespoons per cubic foot of potting mix, or water in by mixing 2 teaspoons per gallon every six to eight weeks.
  • If you’re using liquid humic acids, apply 1 to 2 quarts of Humax per acre, diluted with at least 30 gallons of water for soil application or 6 gallons of water for foliar application. For the home gardener, 1 Tablespoon per gallon of water.

Adding "Whole" Humus to the Garden

Humic acids can also be applied to your garden by adding “whole” humus. Although earthworm castings, compost, and sphagnum moss all contain some humus, an ideal source for this is from Arctic Humus. Although applying humus provides a much lower percentage of humic acids than using leonardite-derived humates, humus does have additional advantages such as providing organic matter, beneficial microbes, and even better water retention than humates. Humates, humic acids, and humus are all great choices at planting time. Just don’t get them mixed up with hummus, which your veggies are dipped in after harvest! Help your garden with humic acids, and grow organic for life!
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Sharon, the frequency of application will really depend on the form of humic acid/humates that you use. The granular or course grade humate can be applied to the planting hole. If you are using the liquid or watering in the micronized (mix with water), then you can apply about every 6-8 weeks. Follow the application instructions on the product label. Your garden will also benefit from adding compost or arctic humus to the soil.


How often should Humacid be applied?

Sharon Brothers

Carol, you can apply humic acid (according to the label) a couple of times a year, probably best during the active growing season, spring and again in late summer.


How often should I apply humic acid to my peach tree. I have clay soil.

Carol Sassaman

When and how much would I apply it to

1) new grapevines going into the ground

2) existing grapevines

John Benson

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