Humic Acid (HA for short) is the remains of animals and plants, mainly the remains of plants, which have been decomposed and transformed by microorganisms. As well as a series of complex geochemical reaction processes and accumulated organic substances. It is a high-molecular organic acid composed of aromatics and various functional groups. It has good physiological activity and functions such as absorption, complexation, and exchange.
Classification of Humic Acid
The main elements of humic acid are carbon, hydrogen, oxygen, nitrogen, and sulfur. It is a condensation polymer of polyvalent phenolic aromatic compounds and nitrogen compounds. Widely distributed in low-level coal, soil, water sediments, animal manure, organic fertilizers, animal and plant residues, etc.
According to the solubility and color classification in the solvent, there are three components:
- The part soluble in acetone or ethanol: brown humic acid;
- The part insoluble in acetone: black humic acid;
- The part soluble in water or diluted the acid part: fulvic acid.
The Functions
① Stimulate physiological metabolism
Humic acid contains a variety of active functional genes, which can enhance the activity of catalase and polyphenol oxidase in crops, stimulate physiological metabolism, and promote growth and development.
- Humic acid can promote early germination of seeds, and the emergence rate is high, especially at low temperature.
- It can stimulate the division and growth of extreme meristematic cells of the root syste. So that the seedlings can root quickly, and the roots are more, the root volume is increased, and the root system is elongated.
- Increase the ability of crops to absorb water and nutrients. Therefore, the crop stems are fast and strong, the branches and leaves are luxuriant, the photosynthesis is enhanced, the transfer of nutrients to the fruiting bodies is accelerated, and the fruits are colored and matured in advance.
② Change the characteristics of fertilizers
Humic acid contains functional groups such as carboxyl groups and phenolic hydroxyl groups, and has strong ion exchange and adsorption capabilities. So it can reduce the loss of ammonium nitrogen in ammonium bicarbonate and improve the utilization rate of nitrogen fertilizers.
- The oxidized and degraded nitrohumic acid can inhibit the activity of urease and reduce the volatilization of urea.
The degraded nitrohumic acid increases the moving distance of phosphorus in the soil, inhibits the fixation of water-soluble phosphorus in the soil, converts available phosphorus into late-acting phosphorus, and promotes the absorption of phosphorus by roots. - Humic acid and insoluble trace elements can undergo a chelation reaction to form humic acid trace element chelates with good solubility. It is beneficial to the absorption of trace elements by roots and leaves.
③ Improve soil structure
Humic acid can promote the formation of soil aggregate structure, adjust soil pH, adjust soil water, fertilizer, air, heat and other conditions. It can increase soil exchange capacity, achieve acid-base balance, improve soil water and fertilizer retention capacity.
Humic acid and promote soil microbial activities. Increase the number of aerobic bacteria, actinomycetes, and cellulolytic bacteria, accelerate the decomposition and transformation of organic matter, promote the release of nutrient elements, and facilitate the absorption of nutrients by crops.
④Enhance the anti-stress characteristics
Humic acid can reduce the stomatal opening strength of plant leaves, reduce leaf transpiration, thereby reducing water consumption, improving the water status in plants, ensuring the normal growth and development of crops under drought conditions, and enhancing drought resistance.
Humic acid is mostly amphoteric colloid, with high surface activity, with below functions:
- Inhibit fungi
- Enhance the coldness of crops
- Be easily absorbed by cell membranes
- Change the permeability of cell membranes
- Promote the absorption of inorganic nutrients
- Prevent rot and root rot
- Reduce pests and diseases
⑤ Improve fruit quality
Humic acid can form complexes or chelates with trace elements. So it can increase the amount of trace elements moving from roots to leaves or other parts.
It help adjust the ratio and balance of macroelements and trace elements, and strengthen enzymes for sugar、starch、protein、the synthesis and operation of fat and various vitamins.
HA can promote the activity of enzym:
- Convert polysaccharides into soluble monosaccharides;
- Increase the synthesis and accumulation of starch, protein, and fat substances;
- Accelerate the transfer of various metabolic primary products from stems, leaves or roots to fruits and seeds, making fruits plump and thick.
