Question

A field of corn has a higher yield (more cobs and more kernels) when a legume such as soybeans was planted in the field the previous year as opposed to when corn was planted in the field the previous year. What is responsible for this effect?

A. nitrogen fixing bacteria in the roots of the corn
		B. nitrifying bacteria in the roots of the corn
		C. nitrogen fixing bacteria in the roots of the soybeans
		D. nitrifying bacteria in the roots of the soybeans

Answer 1

Solution:-

Soyabean plants are legumes. Legumes have bacteria on nodules which are on the roots of plants. The bacteria on the nodules take the nitrogen from the air and fixes it into the soil so that other plants that require nitrogen can use it as well.

Grass crops are unable to take up their own nitrogen from the air so they either need nitrogen in the soil that the legumes provide for them in a crop rotation or they need a chemical fertilizer containing nitrogen. Most farmers do both. They use a two or four year rotation on their field. In two year rotation a farmer will alternate a year of legume such as soybean and a year of grass crop such as corn.

So, the correct option is (c) nitrogen fixing bacteria in the roots of soybeans.