Question

Fairly good yield of rice can be had over a number of years without adding any nitrogenous manures because

• A. They require very minute quantities of nitrogen.
• B. Their roots have nitrogen-fixing bacterial associated with them.
• C. There are nitrogen-fixing algae in the rice fields.
• D. Rice plant do not require any nitrogen.

Answer 1

The correct option is C There are nitrogen-fixing algae in the rice fields.

The rice paddy field contains the Azolla weeds with the nitrogen-fixing cyanobacteria which can help in the conversion of the atmospheric nitrogen to nitrates. This nitrate can be used for the growth of the plants without the introduction of nitrogenous manures externally. These organisms help increase the yield of the rice plants.

Thus, the correct answer is option C.