Question
Hello Long Island Gardener. I would like to know if the effects of humic acid on plants depend on the environment of the types of plants it is used on and the types of plants. Will humic acid work better on plants of the pine rockland habitat, that can adapt to fires and lack of soils, or on regular plants? Thank you.

Answer
Scientist Elaine Ingham, PhD and President/Director of Research at Oregon's Soil Foodweb Inc., works up close and personal with "Humic Substances", the dark matter in Humus, in a routine day at the office.  Humic Substances are Biomolecules -- Lipids, Proteins, Carbohydrates, and Lignin -- that are broken down and left there by the microbes in your Soil.

As I understand it, the Pine Rocklands are an endangered and declining flatlands in South Florida.  The exposed oolitic Limestone substrate grows South Florida Slash Pine and a short list of unique and protected plant species, around 538 taxa in all, presumably with typical mycorrhizal associations, as well as Birds and Animals.  The plight of the Pine Rocklands are described at the Florida Fish and Wildlife Conservation Commission website:

myfwc.com/wildlifelegacy/review/Pine_Rockland.pdf

We have a lot to learn about Humic Acids and their ilk.  Which is why it's nice to have one of the world's foremost researchers chat about them.  I posed your question to Dr Ingham.  Hold onto your hat.  This is what she said:

'Humic acids are complex, highly condensed, long-Carbon chain molecules that usually contain many nutrients in the complex structure.  Generally, because of the complex set of bonds in the structure of this material, and the tertiary structure that is a consequence of being highly condensed, no one enzyme (or even a few enzymes) will be able to attack this material successfully.

'Thus, Humics are food for Fungi and rarely, if ever, are foods that Bacteria can utilize.'

Let's take a step back here and go back to your question.  What you are asking is, Who would appreciate Humic Acids more?  Plants growing on Limestone?  Or potted houseplants?  Do I understand you correctly?

The Mychorrizae of one of your Pine Rockland palms, Serenoa repens, the 'Saw Palmetto', were studied by scientists working in Miami in 1999.  They published their findings in the Plant and Soil journal in a report, 'Root structure and arbuscular mycorrhizal colonization of the palm Serenoa repens under field conditions':

www.virtualherbarium.org/PDF%20Files/PlantSoil217-229.pdf

Arbuscular Mycorrhizae, previously referred to as 'Endomycorrhizal Fungi', penetrate plant roots and form a lacy network of hyphae throughout the Soil in the area, sucking in nutrients (especially Phosphorus) and pouring them into the plant in exchange for the carbohydrates they need.  Glomus, Gigaspora and Scutelaspora Spores were the most common.  Researchers point out, however, that they still have not identified which Fungi colonize Sereneo roots.  'Mycorrhizal colonization promotes Palm growth on nutrient poor native Soil,' noted authors Jack B. Fisher and K. Jayachandran, 'and is potentially significant in the ecology of wild Palms and in the cultivation of ornamental Palms.'  They add later, 'AM are widespread among Palms...The native Soil is Sandy, well-drained, and low in Phosphorus.  Thus, AM could be ecologically significant in Phosphorus and Water uptake.'

So we know that the struggling Palms, at least, in your Pine Rockland habitat struggle less with their Fungal Friends.  Let's return to Dr Ingham's message now:

'As a substance, then, regardless of whether the Humic Acid is used on rock, potting mix or general Soil, Humic Acids will be used as food by beneficial Fungi first and foremost.'  I can only assume Humics would be GREATLY appreciated and utilized to the fullest extent of the law by those AM studied in 1999 in the Soils of Pine Rocklandvania.  Let us continue with Dr Ingham:

'The concern becomes those habitats where the beneficial Fungi are lacking.  There may be no benefit at all in habitats where the beneficial Fungi are low or are not present at all.  Potting mix that has been sterilized is an example of such an environment.  A good Compost or Compost extract or Tea should be used to re-populate the beneficial Fungi.  Then, addition of Humic Acid would also be beneficial.

'Normally, conifers have Mycorrhizal Fungi on their roots, and indeed, conifers will be benefited by addition of Humic Acids, because the Humics help Mycorrhizal Fungi.  It may not be that Mycorrhizal Fungi use the Humic Acids as food, but rather that Humic Acids can be easily used by Mycorrhizal Fungi as sources of P, K, N, Ca, and other mineral nutrients.

'Humic Acids can benefit Grasses and Vegetables as well, in that Humic Acids help grow Fungi that can benefit nutrient cycling and disease suppression, water-holding ability, and Soil structure building.  So there is every reason to add Humic Acids to any system where enhancement of Fungal activity is needed.'

Who needs them more?

Well, if the plant is growing in a bag of potting Soil from the local garden center, it is almost certainly a blank slate with not a microbe to be seen.  Grow it in a pot of U.S. Dirt from the plot outside, and you have something to work with; Humic Acids are a feast for Friendly Fungi.

That said, Dr Ingham urges caution if you are in the market for a commercial bottle of this stuff.  'Be careful.  Humic Acids are usually "stabilized" by addition of low pH Phosphoric Acid.  Make certain to add the right amount of Water to the Humic Acid BEFORE you add any living organisms, or before adding the Humic Acids to Soil, Tea or extract.  The Phosphoric Acid can harm the organisms.  Neutralize the "preservative" or "stabilizer" before use.'  It's imperative, she says, to 'test any Humic Acid to make certain it actually will have a beneficial effect on Fungi.  The folks at Earth Fortifications Supply Company have been testing many [commercial] Humic Acid preparations and finding that many are not beneficial to Fungi in any fashion.  It was a shock to me to find out how many products labeled as high in Humic Acid actually harmed or even killed beneficial Fungi.  Please test the Humic Acid before using it to grow Fungi!  Make sure it actually does function as a Fungal food.'

It's all about the Fungi.  No MA, no Humics.

THE LONG ISLAND GARDENER