Humification - Definition and its Formation

Humification implies humus formation. Humus is a black amorphous material formed by microorganisms' decomposition of dead and decaying organic matter. This definition explains what is humification. 

Humification meaning varies with mineralisation. In mineralisation, inorganic nutrients are recycled, as the name suggests. In order to form inorganic compounds, organic matter can further decompose.

Organic matter is converted into organic polymers in the process of humification, which are stable and cannot be further decomposed by organisms and remain as humus.

Humus

• Humus Definition- Humus is the dark, organic matter found in soil, created when dead plants and animals break down.

• Formation- It forms through the action of anaerobic organisms, which work without oxygen, breaking down plant and animal matter.

• Difference from Compost- Unlike compost, which is made through aerobic decomposition (with oxygen), humus forms in anaerobic conditions (without oxygen).

• Soil Health- Humus is important for soil as it helps retain moisture and nutrients, improving the soil’s overall quality.

• Nutrient Content- Humus contains many essential nutrients, especially nitrogen, which supports healthy plant growth.

• C:N Ratio- Humus has a carbon-to-nitrogen ratio of about 10:1, which is ideal for enriching the soil.

• Use in Agriculture- Farmers often use humus, sometimes called natural compost, to improve soil fertility and as a soil conditioner.

Humification Process in Soil

The humification process in soil takes place by rock weathering, humification of plant remains and laterisation.

1. Weathering

• By chemical or mechanical means, weathering is the degradation of rocks into smaller parts. It is essential for soil formation and growth. The mineral content of the soil is given by weathering. 

• The features of the soil are influenced by such minerals. Chemical rock weathering changes the pH of the soil. 

• Carbonation releases calcium, making the soil more alkaline. The soil texture may also be affected by chemical weathering. Hydrolysis transforms granite feldspar into Kaolin clay that gives a clay-like texture to the soil. Chemical weathering can also influence the colour of the soil. The composition of the soil is determined by mechanical weathering.

2. Humification

• In the humification process, the decomposition of plant twigs, wood, etc. creates humus. Humification determines the consistency of the soil, its colour and texture.

• The humus-rich soil is black or dark brown in colour. Also based on humification is the water content of the soil.

• Humus supports in binding of the soil particles. For the growth of microorganisms, humification preserves the optimal pH in the soil. It enhances soil fertility and the soil's organic content.

3. Laterisation

• It is a type of chemical weathering which includes carbonation, oxidation, and leaching. This natural process can directly affect soil growth, affecting the water content, pH, and structure of the soil. 

• This process is observed to happen in the areas including hot areas such as equatorial settings (The Amazon in South America). The soil texture is influenced by laterisation.

• Mineral grains are dissolved, preventing the formation of the crumbly nature of the soil and therefore leading to the production of platy soils like latosols in turn. 

• The pH of soils is also affected by laterisation. 

• Extreme leaching is found to occur in areas including equatorial rainforests with heavy monsoon precipitation. By the leaching method, the minerals are removed, leaving more acidic soil water in place.

Advantages of Organic Matter and Humus in the Soil

• Humus improves soil fertility by enhancing physical and chemical properties, helping with water retention, nutrient holding, and supporting plant growth.

• By increasing microporosity, humus retains moisture and encourages the development of good soil structure, which aids in plant root growth.

• Humus contains negatively charged sites that attract and bind nutrients like nitrogen, making them more available to plants via ion exchange.

• Humus supports soil organisms’ feeding and reproduction, playing a key role in maintaining a healthy and thriving soil ecosystem.

• The transformation of organic matter into humus helps maintain a balanced soil ecosystem, supporting the coexistence of plants, animals, and microorganisms.

• Stable humus provides immediate nutrient availability for microbes, while effective humus acts as a long-term reservoir of essential nutrients for plants.

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