Question

Which of the following crops would enrich the soil with nitrogen?
A. Apple
B. Pea
C. Sunflower
D. Potato

Answer 1

Hint:- Leguminous crops themselves fix the atmospheric nitrogen with the help of nitrogen-fixing bacteria, which are present in their root nodules.
Around 90% of the nitrogen fixation is impacted by these bacteria, and thus they play a significant role in the nitrogen cycle.

Complete answer: The symbiotic nitrogen-fixing bacteria infest the plants’ root hairs, and multiply there and trigger the formation of root nodules, (enlargements of plant cells and bacteria in intimate association).
Within the root nodules, nitrogen-fixing bacteria convert the free nitrogen to ammonia, which is then utilized by the host plant, for its development.
The roots of the plant are said to have nodules due to the symbiotic association of bacteria.
These bacterial cells consist of the enzyme - nitrogenase. It helps the cells in fixing the atmospheric nitrogen into nitrate salts and therefore, enhances the soil’s nitrogen.

Thus, according to the information mentioned above :-
Option a) Apple - is the incorrect option, since it does not contain nitrogen fixing bacteria in its root nodules, so as to fix the atmospheric nitrogen.

Option b) Pea - is the Correct option, because of the presence of root nodules, consisting of nitrogen-fixing bacteria.

Option c) Sunflower - is the incorrect option, since it does not contain nitrogen fixing bacteria in its root nodules, so as to fix the atmospheric nitrogen.

Option d) Potato - is the incorrect option, since it does not contain nitrogen fixing bacteria in its root nodules, so as to fix the atmospheric nitrogen.

Note:- Leguminous plants like pea, beans, etc. enhance the soil’s nitrogen when they are grown as seasonal crops.
Such plants contain symbiotic nitrogen fixing bacteria like azotobacter, azolla growing in specialized nodes in their roots.
Experts suggest rotating crops with leguminous crops, so as to make the fields nitrogen rich.