What are humic acid fertilizer?

What are humic acid fertilizer?

Published Sep 2, 2019 

Humic acid is a mixture of natural organic macromolecular compounds, which exists in all soils, plants and animals,and have been widely used in agricultural production in recent years due to their unique physiological functions.

The one source of humic acids are the sedimentation layers referred to as Leonardite.

Leonardite is organic matter, which has not reached the state of coal and differs from soft brown coal by its high oxidation degree, a result of the process of coal formation (bog > peat > coal), and high humic acid content as well as higher carboxyl groups.

Now humic acid have been widely used in agricultural production in recent years due to their unique physiological functions.

Adding a small amount of humus to an acre of soil can improve soil condition.

Mechanism of humic acid action

Humic acids range in molecular size from 10,000 to 100,000,and combine mixtures of carbon chains and carbon rings. (In addition to carbon, they also contain oxygen, nitrogen, hydrogen, and phosphorus.)

Humic acids work best in the soil, where they readily unlock nutrients and bind to them, making them available for uptake into plants. And they chelate toxic metals, preventing harmful material from entering the plant.

Also,when foliar applications, humic acid increase the cell wall permeability of plants, which in turn increases the uptake of nutrients.

Features of Humic acid

  • Improves structure of soil, prevents high water and nutrient losses in light or sandy soils.
  • Regulates the pH-value of soils.
  • Promotes the conversion of nutrient elements (N, P, K + Fe, Zn and other trace elements) into forms available to plants.
  • Stimulates root growth, especially vertically and enable better uptake of nutrients.
  • Increases the quality of yields.

What’s more, In addition to these above benefits, its role in plant stress resistance has also received increasing attention.

  • Plant drought stress

Under drought conditions, the application of humic acid-containing fertilizer can promote the increase of proline content in plant leaves to improve the drought resistance of crops.

  • Plant salt and alkali stress

Humic acid can enhance the salt resistance by regulating the change of fructose concentration and alleviating the damage of material membrane under salt stress.

  • Plant temperature stress

Under low temperature stress, humic acid can increase crops’s proline and abscisic acid content, reduce the spead of transpiration rate, stomatal conductance and net photosynthetic rate of plants.

Under high temperature stress, It enhances the heat resistance of crops by increasing the activities of crop superoxide dismutase and peroxidase.

  • Plant disease resistance:

Humic acid can promote growth by increasing the sugar content and chlorophyll content of leaves, which indirectly improves the disease resistance of crops.

Humic acid’s usage and precautions

For flushing, drip irrigation or foliar application,

It is recommended to use potassium humate, ammonium humate or potassium fulvic acid, ammonium fulvic acid.

Mixed with base fertilizer

It is recommended to choose ammonium humate or ammonium nitro-humate.


The humic acid powder can be applied dry, but it is more commonly mixed with water in a watering can, sprayer, or irrigation system.

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