Question

Which of these crops do not require nitrogen fertilizer?
A. Corn
B. Soya bean
C. Grass
D. Oats

Answer 1

Plants are classified by having root nodules. They are under the leguminous plants. This type of plant naturally contains nitrogen fixing bacteria. So, this type of plant doesn’t need any nitrogen fertilizer. The family involved in nitrogen fixing is legume family. In nature the nitrogen is harvested from the atmosphere by microorganisms to form ammonia, nitrites and nitrates which are used by plants for good growth.

Complete answer:
Nitrogen fixation means atmospheric nitrogen is converted either natural or industrial to form ammonia. Three bacteria perform nitrogen fixation. They are Azotobacter , Beijerinckia and anaerobic. Nitrogen fixation is done by lightning, industrial fixation and biological fixation by microbes.
Option A Corn: Corn is under the grass family. Corn needs a large amount of nitrogen to grow hygienic. Sweet corn needs a large amount of nitrogen and phosphorus. The common nitrogen fertilizer is urea. It has $45\%$ nitrogen and easily converts it into nitrate. So, corn needs nitrogen as a fertilizer to grow with high nutrients.
Hence option A is incorrect.
Option B Soya bean: Soya bean is under the leguminous plants. It provides oil and protein. It can grow widely with moist conditions and good organic content. It is the legumes family so it performs nitrogen fixation with the help of rhizobium in the root nodules. It produces nitrogen itself so it does not need any fertilizer. Rhizobium is the group of soil bacteria. It infects the root of the plant to form root nodules. After it attacks the root in the legume family it will automatically fix the nitrogen by using the natural way of nitrogen fixing. After legume dies the nodule will break and it releases the rhizobium to soil so it will re-infect the legume plant.
Hence option B is correct.
Option C Grass: Grass is the large and ubiquitous family of monocotyledonous flowering plants. It needs nitrogen to grow properly and well. Nitrogen fertilizer increases the chlorophyll. It increases the photosynthesis process.
Hence option C is incorrect.
Option D Oats: Oats also need nitrogen as fertilizer to bring healthy and nutrient output. It needs $15 - 20$ pounds of nitrogen per acre. It is a necessary thing for good growth of oats.
Hence option D is incorrect.

Therefore, Option B) Soya bean is the correct answer.

Note:
Organic fertilizers are high in nitrogen including urea. It was derived from urine, feathers and dried blood. Urea has the highest nitrogen content compared to others. The NPK ratio is the important ratio. It describes N- Nitrogen, P- Phosphorus, and K- Potassium. NPK value is $10 - 5 - 5$. So, the nitrogen in the fertilizer must be $5\%$, phosphorus in the fertilizer is $5\%$ and potassium in the fertilizer is $5\%$. It is the correct value for fertilizer for plants.