Question

Identify the constituents of soil.
a. Gravel
b. Salt
c. Mineral
d. All of the above

Answer 1

Hint: Soil is an earth’s uppermost crust which contains mixture of organic matter and minerals. It is a complex mixture of mineral particles, organic matter, soil, air, water and soil microorganisms. The nature and properties of soil varies at different places.

Complete answer:
Soil type or its characteristics depend on the climate of the region, weathering process. Soil factors are also known as Edaphic factors.
The study of soil is pedology. The process formation of soil is known as pedogenesis and it includes:
• Weathering: It is the breaking of rocks into fine particles.
• Humification: It is the addition of organic matter and humus into weathered rocks.
Soil consists of four components i.e. two solid and two non solid. The solid components are mineral particles and organic matter and the non-solid components are air and water.

The proportion of different components is:
• Mineral particles- 40%
• Organic matter- 10%
•Air- 25%
• Water- 25%

There are four types of mineral particles:
• Gravel (fine pebbles): > 2mm
• Sand (quartz and SiO2): 2 - 0.02 mm
•Silt (very fine quartz grains): 0.002 - 0.02 mm
• Clay (hydrated silicates of aluminium): < 0.002 mm

Hence, the correct answer is option (D).

Note: Chief characteristics of the soil are studied with the help of soil profile. Type of soil depends on the climate and vegetation of the area. Soil texture is the physical structure of the soil and it is of three types: Sandy soil (80% sand + 20% clay), Clay soil (50% sand + 50% silt) and Loam soil (20% clay + 40% sand + 40% silt).