Question

Soil is a mixture of
(A) Sand and clay
(B) Sand and humus
(C) Clay and humus
(D) Sand, clay and humus

Answer 1

Soil is made up of varying materials, which are required for supporting life. Apart from supporting life, soil has many other functions to perform such as storing water or moisture, removing impurities, acting as a medium for the growth of microorganisms and plants. Thus, in order to carry out these functions, soil is made up of substances that provide nutrition, in the form of minerals.

Complete answer:
Soil possesses all three state systems such as solid, liquid and gas. 50% of the soil contains solid particles made up of organic and inorganic compounds. The rest 50% contains pores, which contains gases and water. Soil is usually formed by the process known as pedogenesis from a ground rock. The nutritional content of the soil varies greatly according to the parent ground rock.
Generally, soil is composed of sand, silt, clay, humus, iron oxide, carbonate, gypsum, etc. which are found as layers. These layers get mixed up due to human or animal activities. Sand is granular fine rocks which are rich in nutrients. Silt is a fine sand particle that is deposited as sediments from running water. Humus is the organic matter of the soil formed by the decomposition of leaves and other plant materials. This helps majorly in the recycling of nutrients. Clay has a loamy texture which has the ability to hold water, and helps in storage and retention of water.

Hence the correct answer is OPTION(D)

Note: The percentage of sand, silt, clay, humus and other materials varies according to the soil type. But, all the substances are present in all types of soil. Clay forms a colloidal structure which helps the plants to absorb nutrients from it. The mixture of these substances decides the quality of the soil like moisture, nutritional value, water retention, texture, etc.