Question

Why is the uppermost layer of soil black?
A.Due to presence of humus
B.Due to presence of minerals
C.A, B
D.None of the above

Answer 1

Hint:The layers of soil are known as horizons. The uppermost horizon is called a topsoil layer. The topsoil layer is a mixture of sand, silt, clay and broken-down organic matter known as humus. This layer consists of both organic matter and other decomposed materials.

Complete answer:
Soil is one of the most important naturally occurring resources. It is the natural habitat off plants and many microorganisms. It nourishes plants with water and essential nutrients and hence enables their growth. Moreover, soil is the most important raw material for agriculture. Agriculture provides food, clothing and shelter to all entities either directly or indirectly.
The top soil is the topmost layer of the soil. It is dark brown coloured soil which mainly consists of organic matter, decomposed material and many living organisms including some microbes, earthworms and other worms.
However, the uppermost layer of soil is black in color because it contains humus which is a dark brown or black coloured organic matter that contains carbon in high concentration. So, due to the presence of humus, the uppermost layer of soil is black in color.

Hence, option A is correct.

Note:
Two most important properties of soil are their texture and structure. By texture, we mean what soils are composed of and how this affects their cultivation. However, the topsoil can be used to cover the ground and to create new beds, borders or to provide a base for laying or sowing grass seeds. In paved gardens where there is no access to soil, topsoil can be used to raise beds for growing many plants, including vegetables as well.