8.7 - Fertilisers

Why crops have to be fed

• Growing crops take nutrients from the soil as they grow.
• Harvesting removes these nutrients from the field instead of letting them decompose back into the soil.
• Over time, the soil becomes depleted, which slows plant growth and reduces crop yield.

What a fertiliser does

• A fertiliser is a substance added to soil to replace missing nutrients or supply more than the soil naturally contains.
• Replacing nutrients allows the same land to be cropped repeatedly and increases crop yields.

Why fertilisers matter

• The world's population is rising, but agricultural land is limited, so crop yield per hectare must increase.
• Most manufactured fertilisers are made using ammonia.