Question

Deep black soil is considered to be highly productive due to the high proportion of
a. Earthworm
b. Clay and humus
c. Gravel and ${ Ca }^{ 2+ }$
d. Sand and ${ Zn }^{ 2+ }$

Answer 1

Hint: It consists of fine-grained natural soil material present with lots of moisture and nutrients and is best for the agriculture of various crops.

Complete answer:
Black soil is dark brown or black color soil. The black color is due to the presence of organic matter and clay content in the soil. It has a high proportion of clay and humus which makes it fertile. The soil is best for agricultural purposes due to the presence of a large amount of organic matter present in the soil.

Additional information:
1. The black soil is the most fertile because of the presence of the minerals and high moisture content in the soil.
2. Black soils are compact with good hydration but have little aeration
3. A typical black soil is highly argillaceous and swells greatly after the accumulation of moisture.
4. Clay is a type of soil which contains clay minerals, these minerals store water in their mineral structure.
4. Clay can appear in various colors from white to dull grey or brown to deep orange-red depending upon the soil contents.
5. Humus is the dark organic matter that forms in soil when dead plant and animal matter breaks down further through the action of anaerobic organisms.
6. Humus has many nutrients that improve the health of the soil, nitrogen being the most important.
7. Most of the Deccan is occupied by Black soil, it is the best soil for cotton cultivation.

So, the correct answer is ‘Clay and humus’.

Note: Black soil is also called Chernozem which is derived from the Russian word. chernozyom, meaning "black soil". It was first identified by Russian geologist Vasily Dokuchaev in 1883 in the tallgrass steppe or prairie of European Russia. Black soil is also called Regur soil and is important because of its relevance to food security and climate change. The crops grown on the black soils include wheat, jowar, linseed, Virginia tobacco, castor, sunflower, etc.