# Shopping for Humic Acid

- Link: https://rd2.co.nz/shopping-for-humic-acid/
- Published: 2023-03-29T03:59:37+00:00
- Author: RSF Admin

Written by Donald Lester.

In the past humic acids have been referred to as “The Black Gold of Agriculture”.
Due to several watered-down and inferior grades of the product available on the 
market today, humic acids are getting a bad name. These inferior-grade products 
give a reduced performance and as a result, reduced grower confidence. This is compounded
by the fact that are several analytical methods available for measuring etc. the
content and strength of humic acids. For example, California recently decided upon
a particular method of analysis.

When they tested products in the marketplace using this method, they found that 
over half did not rate the strength claimed. Now manufacturers have a six-month 
grace period to change their labels or adjust their products and ingredients to 
pass the new testing procedure. Regulatory agencies in several states are working
to agree on one standardized analytical method used to ensure the consistency of
products in the marketplace. Once this is accomplished, it will be easier to compare
apples to apples when it comes to humic acid products. However, strength is not 
the only consideration when it comes to buying quality humic acid. In this article,
I will point out other important characteristics to look for when shopping for humic
acid products.

Humic acids are a source of concentrated organic matter derived from various sources.
Plant materials go through several stages of decay: fresh plant material, green 
manure, compost, peat, brown coal, leonardite, and coal. These materials accumulate
over time, and with heat and pressure, they eventually form bands or layers in the
soil, each with a different composition of humic acids.

![Screenshot 2023 04 06 at 11.38.57 am](https://rd2.co.nz/wp-content/uploads/2023/
04/Screenshot-2023-04-06-at-11.38.57-am.png "Shopping for Humic Acid 1")

Humic acid is an umbrella term for humic substances. There are two main categories
of humic acids or humic substances: humic acid and fulvic acid. Each group is a 
mixture of large molecules, much like gasoline is a mixture of varying-sized molecules.
Therefore, there is no one recognized chemical structure for humic acid or fulvic
acid. The main distinction between humic acids and fulvic acids is their pH and 
solubility in water. There are theoretical models of the average-sized molecule 
in each group, which gives us an idea of the size and complexity of the compounds.

**“Humic acid extracted from manure or peat is usually not as effective in absorbing
micronutrients as humic acid originating from leonardite.”**

Structurally, humic acids are large molecules containing an abundance of oxygen 
and carboxyl groups. These oxygenated areas on the molecule attract and bind with
trace minerals in the soil that would otherwise be unavailable to the plant. Some
refer to this binding of material as a complex (1:1 ratio), and others refer to 
it as chelation (two humic acids: one mineral ratio). The large humic acid molecule
binds with many mineral ions in the soil to act as a bus to deliver these minerals
to the plant root in a usable form. There are different amounts of oxygenation in
each humic acid source. Leonardite has the most heavily oxygenated molecules yielding
more nutrient-binding sites.

Humic acid extracted from manure or peat is usually not as effective in absorbing
micronutrients as humic acid originating from leonardite. Humic acids have several
properties that are beneficial to plants because they are biostimulants; they chelate
or complex many essential minerals necessary for plant growth; they increase the
seed germination rate; and they act as a food source for beneficial soil micro-organisms.
When it comes to claims, growers often don’t know which to believe. There appears
to be confusion and doubt about the biostimulant effects of humic acids.

The term biostimulant is ill-defined and often thought of as merely a marketing 
term. However, humic acid substances do act as biostimulants (substances that stimulate
growth) in hydroponics and sand cultures, especially in soils with low organic matter
content. Many research studies show that humic substances stimulate the growth of
plant tissues and increase the total quantity of nutrients absorbed. There is a 
large body of experimental evidence for enhanced growth in several crops and in 
different plant parts (i.e. roots, shoots, seeds), but primarily in shoot growth.

One of the more famous humic acid studies is a California processor tomato trial
conducted by Brownell et al. published in 1987 that demonstrated an average yield
increase of 10.5 per cent. The same author conducted cotton trials in the same year
and had a yield increase of 11.2 per cent. Grape trials in large unreplicated tests
had increased yields ranging from three per cent to 70 per cent with an overall 
average of 25 per cent (Magdoff and Weil 2004). In other tests, wheat yields were
reported to increase in ranges of 7.3 per cent to 18 per cent (Xudan 1986). A very
good summary and overview of humic acid research is covered in the book _Soil Organic
Matter in Sustainable Agriculture_ by F. Magdoff and R. Weil published in 2004.

Humic acids also build soil structure. Fulvic acids are physically smaller than 
humic acids. Being smaller in size, the fulvic acids tend to break up heavy clay
soils by absorbing the materials that bind soil particles together. The larger humic
acids tend to bind soil particles together like glue, so they are better at building
and creating soil structure in sandy soils.

![Screenshot 2023 04 06 at 11.43.42 am](https://rd2.co.nz/wp-content/uploads/2023/
04/Screenshot-2023-04-06-at-11.43.42-am-1024x360.png "Shopping for Humic Acid 2")

Of all the raw materials mentioned, leonardite is the best source of humic acids.
Leonardite is a mineral that forms on top of coal beds. It is not to be confused
with the minerals leonhardite or leonhardtite (Jackson, Mehl, and Neuendorf 2005).
In its natural mineral form, leonardite is insoluble and unavailable to plants. 
The humic acids have to be released from leonardite using a solvent. The refining
process of leonardite involves reacting the mineral with sodium hydroxide, aluminium
hydroxide, potassium hydroxide or other alkaline materials. Using sodium hydroxide
results in an average of 7.5 per cent sodium salt in the final product, which can
be toxic to plants and can lead to salt buildup in the soil. Aluminium hydroxide
releases aluminium into the soil, which, under certain pH conditions, ties up or
competes with other nutrients to make them unavailable for plants to use.

Look for humic acids that have been manufactured using potassium hydroxide as a 
solvent because it results in potassium remaining in the final product; potassium
is a desirable essential plant food. Potassium is the K in the N-P-K number of fertilizer
labels. Finally, look for humic acid products that have organic certification. Organic
certification ensures that the humic acid you are buying is not loaded with heavy
metals, pathogenic organisms, animal by-products, sewage materials or other fillers
and impurities.

To view the original paper,** [click here.](https://rd2.co.nz/wp-content/uploads/2023/03/Pub-58.pdf)**