The upper most earth layer is called soil. Plants are fixed to the soil. For healthy growth of plants, air, water and mineral nutrients are required by the plant which is present in the soil.

Observe for yourself

Take a glass and fill it with garden soil to its half. Now pour water and mix it well. Don’t disturb the glass. After some time, what do you observe? Three layers of sand, loam, and clay are settled down. Water along with floating leaf debris is found above these 3 layers.

A white powder remains after filtering and evaporating the water. This is nothing but the slats present in the soil. Taste it. Do you find it salty?

The roots of plants absorb the nutrients dissolved in water. Leaves require carbon dioxide, water, sunlight and nutrients to prepare their food.

Manures and fertilizers; nutrients are reduced in the soil as you grow crops every year. The finished up nutrients should be replenished with fresh nutrients otherwise the soil becomes unfertile. They yield also decreases considerably.

Manure

They are organic manures or natural manures because they are prepared from plant and animal debris. Eg: Dung and urine of cattle, castor oil cake, ground nut oil cake, bone meal, etc. addition of manures increases the fertility of the soil.

Chemical fertilizers

Natural manures take time to decay and release minerals into the soil.

For quick results chemical fertilizers like urea, Ammonium phosphate and super phosphate are used. They are manufactured in factories. The chemical fertilizers are also referred to as `artificial manures’.

Plants need water

Fertilizers dissolve in the soil. The plants absorb them only after they are dissolved in water. For conduction of these nutrients to various parts of a plant, water is required.

Main points

A) The unmannered crops are poor in their growth

B) Manures and fertilizers help in regaining the fertility of the soil

C) The nutrients in the soil are reduced as crops are grown every year, which consume the nutrients present in the soil