Correct Answer - Option 4 : Pulses
Concept:
- Nitrogen occurs as a very stable dinitrogen molecule in the atmosphere, and cannot be taken up by living organisms in that form.
- Hence, it has to be 'fixed' into usable forms.
- Nitrogen fixation is the process of conversion of atmospheric nitrogen into ammonia.
- This ammonia is then converted into nitrites(nitrification) and nitrates which can be taken up by the plants.
Explanation:
Nitrogen fixation can occur by following three different ways:
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Natural: Lightning breaks down the stable dinitrogen molecule into unstable nitrogen ion which can form ammonia
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Industrial method: Nitrogen can be converted in industries to ammonia through a process called Haber's process
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Biological Nitrogen Fixation: Leguminous plants have root nodules which are symbiotic associations between nitrogen-fixing bacteria such as Rhizobium and the plant. The plant provides shelter to the microorganisms which in turn fixes atmospheric nitrogen through the enzymes nitrogenase and the pigment leg-hemoglobin.
Some examples of leguminous plants are: soybean, lentil, peas, etc
- Legumes are rich in proteins.
- The plants usually belong to the Fabaceae family
- The bacteria can be Rhizobium, Nitrobacter, etc
⇒Pulses increase the fertility of soil by fixing nitrogen
