To grow, plants need sunlight, water from rain, CO2 for the air, and nutrients . Where do the nutrients come from?
Nutrients include elements like nitrogen, phosphorous and potassium, that plants need to make parts of their bodies . For example, there is lots of nitrogen in protein . Humans need these nutrients too, but we use them for slightly different things .
Plants absorb water and nutrients through their roots . If there are not enough nutrients, the plants struggle to grow . When the crops are harvested, the nutrients remain in the plant and are gone from the soil. That’s why we use fertilizers  – to make the soil ‘fertile’ again . They are simply a mixture of nutrients that are applied to fields to replenish the missing nutrients .
Unfortunately, fertilizers also pollute rivers , and are a source of greenhouse gases . But no, we should not stop using them. They’re really useful to help grow enough food for everyone, in combination with changes to farming practices . Whilst some farmers could benefit from being able to buy more fertilizers, they are also often used unnecessarily [16,20]. When they are used, problems can be limited by only applying as much fertilizer as the plants will take up, so there’s little excess in the soil [10,11]. A project in China recently managed to reduce fertilizer use by ~15% whilst also increasing yields ! This was done by teaching 20.9 million farmers how and when to plant their crops and use fertilizer .
There are alternatives to fertilizer though! For example, plants called legumes (e.g. peas) hold bacteria in their roots . These bacteria take nitrogen from the air, which is then taken up by the plant and made into proteins . The legumes can then be ploughed into the soil and left to break down, releasing nitrogen into the soil, where it can be taken up by crops the next year . Scientists are also trying to genetically modify other crops, like wheat, so that they can also use bacteria to get extra nitrogen . This would be a huge step forward and reduce the need for artificial fertilizers .
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