Question

Which of the following is not a characteristic of humus?
(a)It is rich in organic matter such as lignin and cellulose.
(b)It is colloidal in nature and serves as a reservoir of nutrients.
(c)It is highly resistant to microbial action and undergoes slow decomposition.
(d)It is further degraded by the process of humification.

Answer 1

Humus is a rich, fertile, and organic substance. It retains the fertility of the soil it is present in and has a unique texture. It is derived from plant and animal remains and also from microbial action. Hence, it also has rich organic content.

Complete answer:
- Humus is an amorphous black-brown soil organic matter that gives fertility to the soil and retains moisture and organic content.
-Dead plant and animal matter together to compose humus. Their decomposition is carried out by the various aerobic and anaerobic microorganisms present.
-The process of formation of humus from raw organic remains is called humification, not the process of degradation. The process of degradation of humus that releases inorganic matter is known as mineralization.

Additional Information: - Since humus contains a large amount of plant remains, it contains organic matter such as lignin, cellulose, sugars, starch, and other substances derived from plant decomposition.
-Humus is colloidal in nature and serves as a reservoir of nutrients as it increases the capacity to hold cations on its surface by chelation. This also prevents them from being lost through rains or irrigation.
-Humus is resistant to microbial or enzyme action because it is hidden or occluded inside small aggregates of soil particles or is absorbed or adsorbed onto the clay.

So, the correct answer is ‘It is further degraded by the process of humification’.

Note: - Humification can occur naturally in soil or can be induced artificially in the production of compost.
- It has been observed that most humus does not decompose by microbial action or even into simpler compounds and persists in the soil.
- Due to the presence of the various organic and inorganic substances, humus acts as a natural buffer and prevents excess acidity or alkalinity.