Role of humic acid in plant growth and soil quality

Humic acid is the commercial term that is often used to refer to the combined humic and fulvic acid contents present in these naturally occurring deposits.

Role of humic acid in plant growth and soil qualityHumic acid is one of the most biochemically active material present in soil. Humus is the complete mixture of brown to dark color amorphous substances that have been derived during the decomposition of plant and animal residues by microorganisms, in soils ,compost ,peat, bogs and water basins.

Chemically it consists of specific constituents of basic plant material resistant to more decomposition, of substances which result from decomposition be the processes like hydrolysis or by the oxidation and reduction and of different compounds manufactured by microorganisms.

Why Humic Acid?

Now a days, humic acid is being used increasingly for the better plant growth and cultivation of different crops. It is also used in soils which lack organic matter.It is not a fertilizer because it does not provide nutrients directly to plants.


  • It adds organic matter to the soils.
    Root vitality is increased.
    Nutrients uptake is increased .
    Speed up chlorophyll synthesis.
    Availability of fertilizer to crops is increased.
    Microorganisms become active.
    Healthy crops and production increased.

How Soil Improvement Occurs?

When humic acid applied to clay soils causes the breakdown of compacted soils . By this water penetration is increased and root development Is improved. In sandy soils it provides necessary organic matter. Prevents the leaching of plant nutrients.

Role of Humic acid In Microbial Activity:

Microbial activities play a key role in plant growth. It provides microbes with carbon source of food which stimulate microbial activity. This process boost up their growth and activity. Microbes solubilize essential nutrients and make them available to the plants.

Role in Fertilization:

Basically it is not a fertilizer but in some fields people consider it a fertilizer. It is used as a complement to synthetic or organic fertilizer. In some cases , regular use of humic acid will cause reduction in use of fertilizer , due to soils and plants ability to make its proper use.

When humic acid is applied it increases microbial activity and humus production due to which fertilizer usage is entirely reduced.

Plant Growth:

Humic acid play beneficial role in freeing up the nutrients in the soil to make the availability of nutrients to the plants.For example if P is linked with Al it separates them and make the P available to plants. Provides the chelate micronutrients to plants .

Economic Outcomes:

As mentioned above due to application of humic acid nutrients availability is enhanced and thus use of pesticides and fertilizers is reduced.

One of the significant feature of the humic acid is that it binds to insoluble metal ions, oxides and hydroxides and provide them to plants when needed. Due to this property it produces three types of effects

Physical Effects:
1- Reduces soil cracking
2- Loosen the soil
3- Increases water holding capacity
4- It makes the soil dark colored so absorption of sun’s energy is increased

Chemical Effects:
1- Buffering property of soil is enhanced
2- Under alkaline soil condition it works as a natural chelator
3- Makes the micro and macro nutrients in available form to plants
4- Chlorosis does not occur because of iron deficiency in plants
5- Toxic substances availability to plants is minimized.
6- Maintain the pH value

Biological effects:
1- Increases enzymes production.
2- Root formation and root respiration rate enhanced.
3- Seed viability and germination is promoted.
4- Synthesis of essential bio-elements is increased.
5- Vitamin and minerals contents are increased.

Ecological Benefits:
1- Low nitrate leaching occurs.
2- It prevents nitrates and pesticide mixing with underground water.
3- It is less hazardous to environment.

It decreases high salt contents from soil and minimizes soil toxicity.
Root burning is reduced which occurs due to more salt contents in soils after fertilizer application. Additionally when humic acid is mixed with any liquid fertilizer the unwanted odor is minimized.

Authors: Muhammad Ayoub, Amir Shehzad and Zain-ul-abidin Gilani
Corresponding Author: Muhammad Ayoub

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