Question

Humus is an example of
(a) Soil structure
(b) Organic colloids
(c) Crystalloids
(d) None of these

Answer 1

Hint: Humus is colloid of tiny particles with long carbon chains and is made from the microbial decomposition of the substances present in plants and animals.

Complete answer:
Humus is an example of organic colloids. Organic colloids are tiny particles of organic matter that can not decay further or that are resistant to decay.
- As the soil particles are different colloids are also different. Some colloids are made up of minerals, whereas others are made of organic matters.
- The mineral colloids are usually crystalloids or refined clay particles.
- Different types of Soil Colloids are:
1. Crystalline silicate clays- crystalloids
2. Non- crystalline silicate clays
3. Iron and aluminum oxides
4. Organic (humus) colloids
- Humus has got a very important place in the growth and development of plants because it keeps the soil moist. It is very much valuable for farmers and gardeners because it provides essential nutrients for the growth of plants, also increases the water absorption power of the soil, and improves the working ability of soil.
So, the correct answer is, ‘organic colloid’.

Note:
- The color of humus varies from brown to black. It consists of about 60 percent carbon, 6 percent nitrogen, and very small amounts of phosphorus and sulfur.
- It does better aeration of soil by loosening it and also results in drainage of water to the underground water table.
- Humus also encourages the increase of those soil organisms that helps to make the soil more nutritious for plants.