micronutrients "bioavailable" to plants.
Fungi also play a role in this, especially for fruit trees, but definitely not limited to fruit trees.
Now "science" is actually looking into what is known by organic farmers. An inconsistency remains in whether these are high molecular weight or low molecular weight....we shall delve into that another time.
Fulvic acids are natural, water-soluble polymers, which are the ingredients of humic substances defined as “a series of high molecular weight substances, yellow to black in colour, formed as a result of secondary synthesis reactions” [1,2]. They are complex substances without standard chemical formulae, which are present in soil and plants in trace amounts [3,4].
They are formed during the decomposition of decaying plants by microorganisms and they play essential functions in plants; e.g., are responsible for the absorption of nutrients and trace substances. Naturally, fulvic acids contain minerals (more than 70), amino acids, sugars, peptides, nucleic acids, phytochemical compounds, vitamins, and fragments of plant DNA .
Most of them occur in ionic form. This means that fulvic acids conduct electricity excellently and improve the absorption of other compounds interacting with them. Moreover, because of ionic minerals, fulvic acids help to increase their bioavailability in plants . Fulvic acids are also chemically reactive because of the presence of many carboxyl and hydroxyl groups . Due to their low molecular weights, they can transport minerals to plant cells in the root, stem, and leaves . They also participate in the carbon cycle, because they are constantly recycled among plants, soil, and water .