Soil organic matter comprises the decomposing plant and animal residues.
This organic material contains microbial synthesized compounds and other derivatives produced from the microbial activity.
An excellent organic matter is one that is completely decomposed. This decomposed material is also called humus.
Organic matter improves the soil’s physical structure and increases soil water movement and provides proper aeration by making the soil loose.
What is soil organic matter
This soil organic material is the material formed from dead plant and tissue matter.
It is especially made from the plant tissues, leaves, branches and roots.
Hence, the plants form the primary source of organic matter while the animals act as the secondary source of organic matter. The decomposition process mainly occurs due to the bacteria and fungi present in the soil.
Composition of Soil Organic matter
The organic matters consist of both organic and inorganic materials.
Organic materials include the nitrogenous organic compounds (Water-insoluble – protein, peptides and water-soluble – nitrate) and non-nitrogenous compounds.
Inorganic materials are the minerals present in the soil like the calcium, magnesium, potassium, copper, etc.
Decomposition of Organic matter
The dead plant and animals matter which lie on the earth’s surface comes in contact with the soil and the water present in the soil.
The decomposition of these materials occurs slowly. However, the microbes boost the process by releasing enzymes that help in the breakage of the organic materials.
Microbes absorb the nutrients released during decomposition. The compounds of especially nitrogen and carbon are used for their growth and multiplication.
The rate of decomposition is directly affected by the number of the microbes population. The higher the microbes, the faster is the decomposition.
The decomposition is also affected by the presence of nitrogen and carbon compounds in the decaying materials.
Factors affecting decomposition
Important factors regulating the decomposition of the organic residues in the soil are
- Temperature – Temperature directly affects the rate of decomposition. The rate decomposition of organic materials increases with the increase in temperature and vice verse.
- Soil moisture – Moisture in the soil and atmosphere favors the decomposition process.
- Soil reaction – Soil reactions affect the microbial activity and thereby affecting the decomposition of organic residues. Generally, pH 6-8 is optimum for the organisms. The decomposition of organic matter is slow under acidic and basic soil conditions.
- Soil texture – Soil texture indirectly influences the rate of organic matter decomposition.
The functions of organic matter
- Organic matter reduces the loss of surface soil due to erosions by forming granules with the soil particles.
- Organic matters influence the color of the soil. Presence of organic matter in the soil gives a dark black color to soil
- Organic matter increases soil fertility.
- The organic matter enhances the soil water holding capacity.
- Organic matter binds soil particles to form aggregates; these aggregates help to maintain the porosity of soil and maintain the aeration in the soil.
- This organic matter maintains the pH of soil
- Organic matter reduces plasticity, cohesion, stickiness, etc. in soil.
- During decomposition of organic matter, various organic acid and CO2 liberate in the soil which helps to reduce the alkalinity of the soil.
- Organic matters are the storehouse of various nutrients that are essential for the growth of plants.
- Organic matters are the source of energy for microorganisms.
Management of organic matter in soil
- Tillage – reducing tillage minimizes the loss of organic matter from the soil. Tillage is done for field preparation, but this process affects the soil structure.
- Ground cover – by covering the ground, we can prevent the loss of organic matter from the surface erosion by the wind and water.
- Addition of organic matter- The addition of more organic matter in the soil will recover the organic matter which was lost.