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Fulvic and Humic Acid Testing- Comparing Apples and Oranges?

Updated: May 10, 2023

I was walking through my local specialty gardening store aisle looking for a good fulvic acid for my garden. One bottle from a big brand name claims 0.1% humic acid from Leonardite, while another leading brand claims 1% weight by weight total humates on the label. With such confusing labels how am I supposed to find a good quality humic or fulvic acid product?

Let’s start with some information on the source material, humic substances. It is organic material that has been degraded over millions of years under low pressure found often found in oxidized lignite, shale, peat and mud sands. It contains humic acids, which is high molecular weight, soluble in alkaline conditions and are typically dark in color. Humic acid is also found with fulvic acid, which is light molecular weight, soluble at all pH levels and are typically a lighter yellow color.

Label confusion is introduced because there are different components that tests are looking for with little consensus on which method to use. There are several methodologies to determine humic and fulvic content, but we will go over three of the most common.

The first test is CDFA, developed by the California Department of Agriculture. It separates the humic and fulvic acid, recognizing only the humic acid and insoluble ash in the results. The sample can test very high if it is high in non-humic substances in the ash content. To add further complications, this method is the only approved method for labeling in California and Oregon.

The second notable test is Verploegh and Brandvold, which known as the V&B method. It is a variation on the “Classical Method”. It can test humic and fulvic content. It is a bit more accurate removing insoluble material, but also includes the additional chemical reagents, lipids, carbohydrates proteins, and amino acids leading to higher, but skewed test results.

The final test of note is the International Humic Substances Society (IHSS) test also known as the Lamar method. It is also used by the AAPFCO. It is more rigorous, removing insolubles, chemical reagents and separates the humic and fulvic in the test results. It is the most accurate and most agreed upon method, but is more expensive and takes longer compared to other methods.

When looking for a good humic and fulvic additive, ask the company on the label:

  1. Is your humic and fulvic additive pure water extracted, or does it contain chemical processing that may skew results?

  2. What testing method does that product use?

  3. Is the company willing to send you a copy of the results?

There are a lot of choices out there for fulvic and humic additives. Companies using the Lamar method are going to be the most accurate for hard-earned money being spent on inputs in the garden. Regardless of the testing method, ask yourself – is your supplier transparent with customers about what goes into their product?

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