(i) Silica: The main constituent of sand, it is present as small crystalline grains. It is mainly derived from the weathering of rocks.
(ii) Clay: It is a mixture of silicates and contains many minerals like iron, potassium, calcium, sodium and aluminium. Particles of clay absorb water and swell.
(iii) Chalk: It consists of calcium carbonate which provides the important element calcium.
(iv) Humus: It is the organic matter present in the Soil formed by the decomposition of plants and animal remains and animal manure. It is the most important element that determines the fertility of the Soil.