Testing Methods – What difference does it make?

As a grower, how do you determine quality humic acid products form less effective “imitation” products?

Having an understanding of the various testing methods is a good place to start. As we mentioned, there is no universal standard for testing humic content and the percentage of humic acid in a product can be over-estimated by co-formulants such as kelp, NPK fertilizers, coal, molasses and lignosulfonates. The accuracy of content percentages is determined by the analysis methodology.

When shopping for the right humic products for your soil, the percentage of humic content is a big deciding factor. Not only does it dictate strength and application, but also impacts the results you’ll see. However, depending on the testing method used to come up with these marketable numbers – certain methods can mislead the consumer into think the percentage of humic acid is higher than what is actually produced.

As wider adoption of humics takes place, more new humic-based products are appearing in the marketplace – often with varying claims of humic and fulvic content.

So, how are these humic content claims determined?


Unfortunately, currently there is no universally standardized method for analyzing humic and fulvic acid content at regulatory agencies. Many humic and fulvic products, especially liquids, contain additives such as lignosulfonate which can mimic humic and or fulvic acid and can artificially elevate test levels under some analysis methods.

There are three primary testing methods when it comes to humic products


  1. Colorimetric Method

The Colorimetric Method is a simple qualitative test for humic substances. Currently it is the most popular and widely accepted method of testing as it is used for registration and labelling in most US states and Canadian provinces.

Colorimetric analysis is a fast and convenient method compared to other testing methods. All you need is a colorimeter which is a light-sensitive, and it calculates the concentration of a substance, such as humics, based on the intensity of the colour and how much light passes through the solution.

Unfortunately, this test is not always the most accurate. This test typically gives a higher humic content result than other methods. The humic percentage can be overestimated by co-formulants such as kelp, NPK fertilizers, coal, molasses and lignosulfonates. Another disadvantage of this method of analysis is that it is not capable of distinguishing fulvic acid from humic acid.

  1. The CDFA method

The California Department of Food and Agriculture (CDFA) method is a quantitative method that analyzes humic acid levels only. This method is much more effective at detecting non-humic additives, so as a result, most sulfonated products will show a much lower humic acid content percentage.

While the CDFA method is considered a much more accurate method than the colorimetric, the CDFA method does not account for any fulvic content or does not adequately account for ash content. Products with high ash content can appear higher in humic content.

The CDFA method is not nearly as widely accepted as other testing methods. Currently this method is only used by California and Oregon for product registration and labelling requirements of humic acid products.

  1. HPTA Method

The HPTA method is currently considered the most accurate testing method to determine humic acid content. This method was recently developed as a quantitative analysis of humic acid that has been approved by the “Journal of Association of Official Agriculture Chemists” and now is adopted and recognized by the International Standards Organization as ISO method 19822.

Currently, this method is considered the most accurate analysis of humic content and is being proposed as an industry-wide standard by the Humic Product Trade Association.


So, how do you judge the quality of your humic products?

The lack of standardized testing method can make it difficult to make accurate comparisons of different products. Your supplier should be able to let you know which methods they use for their label claims an also how their products test under different testing methods.

We always encourage our customers to educate themselves on how humic products are tested. There are many great products out there on the market – make sure you are investing in quality.