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NCERT Exemplar · Q52

Q.What are biofertilisers? Give two examples.

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Biofertilisers are living microorganisms that enrich soil fertility by fixing nitrogen, solubilising phosphorus, or stimulating plant growth — they are a natural, eco-friendly alternative to chemical fertilisers.

Biofertilisers are not fertilisers in the conventional sense. A chemical fertiliser directly supplies nutrients like nitrogen, phosphorus, or potassium to the soil. A biofertiliser, on the other hand, contains living cells of microorganisms that, when applied to seeds, plant surfaces, or soil, colonise the rhizosphere (the root zone) and promote growth by increasing the availability of essential nutrients to the host plant. The key idea is that these microbes do the work of converting atmospheric nitrogen into a usable form, or of unlocking phosphorus that is otherwise bound in the soil, without the environmental damage caused by synthetic inputs.

The NCERT textbook emphasises that biofertilisers are especially valuable in sustainable agriculture. They reduce our dependence on energy-intensive chemical fertilisers, improve soil health over the long term, and are cost-effective for small and marginal farmers. They are not a magic bullet — their effectiveness depends on soil conditions, moisture, and the specific crop — but they represent a crucial tool in integrated nutrient management.

Note

The term "biofertiliser" is sometimes loosely used for compost or vermicompost. Strictly speaking, those are organic fertilisers, not biofertilisers, because they do not contain living microbial inoculants. The NCERT draws a clear line: a biofertiliser must be a living preparation.

Now, the NCERT provides several examples, but two of the most important and widely used are:

1. Rhizobium – This is a symbiotic bacterium that lives in the root nodules of leguminous plants (peas, beans, groundnut, soyabean, etc.). It fixes atmospheric nitrogen into ammonia, which the plant can use. In return, the plant supplies the bacterium with carbohydrates. This mutualistic relationship is one of the most well-studied examples in biology. Farmers often treat legume seeds with a Rhizobium culture before sowing, ensuring that the bacteria are present in the soil from the start. …

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