Back to: MBOSE Science Class 7

Soil is one of the most important natural resources. It is necessary for the growth of a diverse variety of plants, trees and flowers. Soil helps the plants by holding the roots firmly and providing water and nutrients so that they can prepare their food. Soil is essential for agriculture.

Soil is formed by the breaking down of rocks caused by the action of wind, water climate and plants. This process is called weathering.

The four components of soil are minerals, organic matter, water and air. The typical soil consists of approximately 45% mineral, 5% organic matter, 20-30% water, and 20-30% air.

The different types of soil and their uses are as follows.

Sandy Soil: This soil contains a large amount of sand particles and very small amounts of silt and clay particles. This soil is highly porous because the particle size is large. This type of soil is thus a well aerated soil. The water retention of this type of soil is poor, as it drains off quickly through the spaces.

Clayey Soil: This soil consists mainly clay particles and a small amount of humus and silt. Clay particles are fine and there is ales gap between the particles. This soil is heavy and dense. It has water retention and becomes sticky when it is wet. Clayey soil is used for making toys, pots, statues etc.

Loamy Soil: This is the perfect soil for growing plants. It is a mixture of sand, clay and silt. Silt is a deposit in river beds. Loamy soil has the right water holding capacity and has enough space for air. It also contains humus and good for growth of plants.

Loamy Soil is best for growing plants. This is because the loamy soil has the right water-holding capacity and has enough space of air. It also contains of humus and good for growth of plants.

Names of five organisms that live in the soil are: Ants, Earthworms, Archaea, Algae, and Protozoa.

Sandy soil is not good for growing crops. This is because it cannot hold the water and it has big soil particles and it is found in desert area.

Soil Erosion: The process of removal   of top layer of soil by wind or by the flowing water is called soil erosion.Causes of Soil Erosion:

The main causes of soil erosion are

So we must prevent cutting of trees and deforestation and the same time we must plant more trees and grass.

Soil important for plants: Soil is important for plants because it provides foothold for their roots and holds the necessary nutrients for plants to grow.

Three factors responsible for Soil erosion:

• Human factor: Deforestation, overgrazing and mining.
• Natural Factor: Wind, Glacier and water.
• Other factor: Ploughing in a wrong way and defective methods of farming.

Jhum Cultivation is also known as Shifting Cultivation: Jhum cultivation is a major cause of deforestation. This practice of cultivation of crops is generally found in hilly regions. A large area of forests is cleared by burning of trees for cultivation. Jhum cultivation is also known as slash and burn agriculture. During slash and burn, the organic matter in the soil gets destroyed and most of the nutrients are taken. Thus, making up the crops within a short period makes the cultivator shift to another area. This practice of agriculture is known as shifting cultivation.

Effects of Jhum Cultivation: The effects if Jhum cultivation are- Due to the soil turns barren and dry, the water holding capacity of the soil and fertility of the soil also decreases.

We say that the sand is well aerated. This is because the water retention of this type soil is poor, as it drains of quickly through the spaces. So, sandy soils tend to be light, well aerated and rather dry. Clay particles, being much smaller, pack tightly together, leaving little space for air.