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Question
A farmer was planting wheat crops in his field. He added nitrogen-rich fertiliser to the soil to get a good yield of crops. In the neighbouring field, another farmer was growing bean crops, but she preferred not to add nitrogen fertiliser to get healthy crops. Can you think of the reasons?
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Answer
The wheat field
The bean field
Wheat is not a legume.
Bean is a legume.
Its roots have no nodules.
Its roots have nodules holding
Rhizobium
.
No bacteria to trap nitrogen from the air.
Rhizobium
traps nitrogen from the air.
So nitrogen-rich fertiliser must be added.
So no nitrogen fertiliser is needed.
Beans are legumes, whose root nodules hold
Rhizobium
bacteria that supply nitrogen naturally.
Explanation
- Bean is a legume with root nodules.
- Rhizobium bacteria in these nodules trap nitrogen from the air.
- This nitrogen enriches the soil, so the bean farmer needs no fertiliser.
- Wheat has no such bacteria, so that farmer must add nitrogen fertiliser.
Rhizobium
in bean roots adds free nitrogen, so no fertiliser is needed.
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