Bioactivity of Humic Acid
The biological activity of humic acid can be divided into two categories,
- Indirect Bioactivity
It refers to the effect of humic acid on plant growth through soil media including the improvement of soil physical properties, enhancement of fertilizer efficiency, metal complexation, reduction of phosphorus fixation, buffer of soil salt, influence of soil microorganisms and enzymes, etc.
- Direct Bioactivity
It refers to the effect of humic acid on plant growth itself including promoting the activity of the plant root system, enhancing the absorption, accumulation, and transformation of beneficial elements in the plant body, promoting respiration and enzyme activity, and improving the ability of stress resistance.
The mechanism and source of humic acid bioactivity mainly include,
- Oxidation-reduction property of humic acid itself.
- Effects of humic acid on plant enzymes and auxin.
- Humic acid can improve cell membrane permeability and promote plant nutrient absorption.
- Some substances associated with humic acid are hormones or parahormone themselves, such as succinic acid, folic acid, amino acid, aminopurine, etc.
However, unprocessed natural humic acid(leonardite) is insoluble in water and has low biological activity. Only by oxidizing and activating it, cutting its macromolecules into small molecules soluble in water, and increasing the content of functional groups, can humic acid give full play to its biological activity.