Olympiad Test: Soil

Soil is a mixture of clay, rocky particles and organic remains of plants and animals. It forms the upper layer of the surface of the earth i.e. it covers the land. Soil is formed from the weathering of rocks. Different types of soils are present depending upon the climatic conditions of the place and different composition of gravel, clay etc. in the soil. The topmost layer of soil called humus is the most fertile as it contains nutrients for the growth of plants. Soil is a shelter for many microorganisms. Hence, soil is an important natural resource.

The amount of water retained by soil per unit volume is called as water holding capacity. It is highest in the clayey soil.

In addition of the rock particles, the soil contains minerals, organic matter, air and water.

The decayed organic matter in the soil form humus which is black in colour.

The process of removal of top soil due to action of air, water etc. is called soil erosion.

Volcanic soils are soils in which more than half of the parent mineral matter is volcanic ash ans appear very dark in colour.

The process of breaking down big pieces of rock into smaller pieces is called weathering.

Type of soil depends upon the rock from which soil is formed. Basaltic rock forms the black soil.

The soil suited for cultivation of wheat, rice and sugarcane is called alluvial soil.

The weathering of soil takes place in O-horizon of soil profile.