3rd Class Science Soil Notes - Soil

Soil

1. Soil is formed by the breaking up of rocks. By the action of sun, wind and rains rocks are broken down into small pieces. The acids produced by the roots of plants also help to break down the rocks. These pieces of rocks are carried to other places by running water and strong winds.

2. Different places have different types of soil. The type of soil depends upon the kind of rock from which it is formed. Soils differ in the size of the grains and different constituents present in it.

3. Most of the soils contain coarse particles of gravel, small pieces of stones, sand particles clay, moisture and humus. Humus is made up of rotten leaves and decayed bodies of plants and animals. Humus is dark brown or black in colour.

4. There are four kings soil: gravel, sandy soil, clay and loam.

5. Gravel is made up of very large grains which do not hold any water between them. They hold a lot of air.

6. The sandy soil has grains smaller than those of gravel. It is grey or brown in colour. The particles are lossely packed and there is lot of air in the spaces between the particles. If we pour water on a heap of sandy soil, water sinks quickly. Sandy soil is mostly found in the deserts and on the beaches. Water drains easily through sandy soil.

7. Clay is made up of very fine grains which stick together. Clay can hold a lot of water but very little air. Clay is used for making toys and other articles.

8. Loam is a kind of soil which we get if we mix equal amount of sand and clay. Loam can hold enough water and air for the use of plants. Loam to which humus has been added makes a soil which is best for the growth of plants.