Question

Azolla is useful as green manure for
(a) Wheat
(b) Rice
(c) Maize
(d) Coconut

Answer 1

A genus of seven species of aquatic ferns in the family of Salviniaceae can be termed as Azolla. Such plants are said to be extremely reduced in form and specialized. Their appearance is nothing special and they look alike the other typical ferns. However, they are also resembling the plants like the duckweed or some types of mosses. On brief research, one can say that one of just two fern species for which a reference genome has been published is Azolla filiculoides.

Complete answer:
Azolla can be used as green manure in the duration of cultivation of crop rice to increase the yield of the rice crop. As we mentioned earlier, the plant of Azolla has belonged to the family of Salviniaceae.

We can say that such plants are aquatic ferns which remain in a symbiotic relationship with the animals like Anabaena. It also helps in the process of fixation of nitrogen. Its role is to provide a safe environment for the cyanobacteria in exchange for nitrogen.

For the crops like wheat, the red clover provided multiple benefits over hairy vetch and triticale in the role of green manure. The nitrogen can be the green manure to the legumes plant like maize. The Crotalaria striata which is a leguminous weed can be used as green manure for the coconut plants.

Hence, the correct answer is option (B).

Note: Azolla is chosen as the main green manure to rice crops. It is because it provides a variety of benefits for rice production. It is grown in such a way that is complementary to rice cultivation. It is said that the thick Azolla mat in rice fields is capable of suppressing the weeds.