Question

Soil is the source of many nutrients and minerals, nitrogen is one of the elements that is required by plants in different forms for their proper growth. Have you ever wondered where does this nitrogen in soil comes from?

• A. micro-organisms add atmospheric nitrogen in the soil by a process called nitrogen fixation.
• B. plants manufacture the nitrogen required by them by a process called nitrogen fixation.
• C. soil itself absorbs nitrogen from the atmosphere by a process called nitrogen fixation.
• D. plants add nitrogen to the soil through their roots by a process called nitrogen fixation.

Answer 1

The correct option is A

micro-organisms add atmospheric nitrogen in the soil by a process called nitrogen fixation.

Nitrogen is required by all living organisms for the synthesis of proteins, nucleic acids and other nitrogen-containing compounds. The earth's atmosphere contains almost 80% nitrogen gas. It cannot be used in this form by most living organisms including plants until it has been fixed, that is reduced (combined with hydrogen), to ammonia.
Nitrogen fixation is done by bacteria present in the soil. Green plants, the main producers of organic matter, use this supply of fixed nitrogen to make proteins that enter and pass through the food chain.