Important crop plant such as wheat and corn do not have useful relationship with rhizoba . Instead they rely on nitrates in the soil as a source of nitrogen . Fertilizers are used to increase the nitrate concentration of the soil and increase crop yield . Explain how crop rotation will help in this sitiuation

Crop rotation will help in fixing the nitrate in the agricultural field with the help of rhizoba bacteria

Explanation:

The crops of  wheat and corn do not have any relationship with the rhizobia which means they depend on soil for their nitrate requirement.  

Now Rizhoba interacts with the leguminous crops such as pulses to capture the atmospheric nitrogen and convert & store it as nitrates with in the roots of leguminous crops.  

Thus, in order to get nitrate from soil for wheat and corn crop, leguminous crop must be grown before these two crops in the field so that rizhoba fixes sufficient nitrate in the soil . In this way crop rotation will enhance the yield of wheat and corn

i think the answer is b.

hope it