Question

Why are leguminous plants cultivated as a green manure crop?

Answer 1

Hint: They contain specialized nitrogen-fixing soil bacteria that help them to fix nitrogen and are then absorbed by plants for fulfilling their nutrient requirements and after their death, it is transferred to the soil making it fertile.

Complete answer:
The leguminous plants belong to the family leguminosae also known as the bean family or the pea family. These plants consist of legumes in their root hairs where several nitrogen-fixing bacteria are present, more specifically rhizobium bacteria that help the plant in nitrogen fixation. The nitrogen from the atmosphere is absorbed by the nitrogen-fixing bacteria which is then converted into ammonia. Ammonia is the form of nitrogen that can be easily absorbed by the plants for nutrition.
After the death of the plants, decomposition takes place that leads to the release of nitrogen into the soil which is then converted into nitrates and the denitrifying bacteria that are present in the soil will convert it into nitrogen and then transport it back to the atmosphere thus complete the nitrogen cycle and it results in the maintenance of soil fertility.
This process may result in the formation of the green manure in the soil that makes the soil more fertile, humid, and best for growing crops. The legumes after they are harvested there uprooted plants or the withered leaves are left in the field where they will decompose and form manure which is added to the soil. The leguminous plants are mainly cultivated for the purpose of forming green manure after they get germinated shortly and then sown in the soil.

Note: The use of green manure was practiced since ancient times in India and also China and Greece to increase soil fertility. Earlier the use of green manure into the soil for the purpose of crop rotation is called the fallow cycle. The fallow cycle is leaving the land for one or two seasons so that the fertility of the soil is regained.