Question

Explain the scientific reason for growing Azolla pinnata in a rice field.

Answer 1

Hint: Azolla pinnata is a small species of free-floating freshwater fern typically found on the surface of small ponds or backwaters without any wave action. It usually spreads rapidly by keeping on doubling every 5–7 days.

Complete answer:
Azolla pinnata is especially grown in wet soil in rice fields during rice cultivation to generate a good amount of nitrogen rich fertilizer. The association of Azolla pinnata along with the blue green algae called Anabaena provides great importance to agriculture. The application of Azolla in rice paddy fields by rice farmers increases the productivity of rice by more than 50% thereby it is used as a nitrogen-rich biofertilizer and weed suppressant.

It is because of its nitrogen fixing abilities during its symbiotic relationship with the blue-green algae called cyanobacteria. As this fern does not interfere with the growth of rice crops but increases its yield, rice cultivators sometimes keep this plant Azolla pinnata in the rice field of their paddies to coexist with the algae for its ability to fix atmospheric nitrogen in rice paddies.
There is an increase in the availability of fixed atmospheric nitrogen, when it is assimilated by Azolla-Anabaena in the cavities for the growth of rice plants. This type of fern plants, even when it is decayed, releases the same amount of nitrogen fixation for rice plants.

Note: When the paddy field becomes dry at the time of harvesting period, then this aquatic fern, Azolla Pinnata plays a great role in functioning as a green manure in order to maintain the fertility of the soil. It acts as a renewable biofertilizer not only in paddy fields for growing the productivity of certain crops but also helps to influence soil fertility by decomposing itself rapidly and its nutrients are released in the water to enrich the soil as well as the field suitable for the next crop.