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- Increasing crop yields
Increasing crop yields
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Farmers control the conditions plants grow in, add minerals and control pests to grow more food.
Glasshouses and polythene tunnels
They keep crops warmer, protect them from bad weather and some pests, and allow a longer growing season.
Growers can raise the carbon dioxide concentration (for example with paraffin burners, which also release heat).
Higher carbon dioxide and temperature increase the rate of photosynthesis, so the yield increases, until another factor becomes limiting.
Growers can raise the carbon dioxide concentration (for example with paraffin burners, which also release heat).
Higher carbon dioxide and temperature increase the rate of photosynthesis, so the yield increases, until another factor becomes limiting.
Fertilisers
Fertilisers replace the mineral ions (such as nitrate, phosphate and potassium) that crops remove from the soil.
They may be natural (manure) or artificial. More minerals mean more growth and higher yield.
They may be natural (manure) or artificial. More minerals mean more growth and higher yield.
Pest control
Pests eat or damage crops and reduce yield.
A grower raises the temperature in a glasshouse but the yield does not increase. Suggest why.
- Another factor may be limiting photosynthesis.
- For example, carbon dioxide concentration or light intensity may be too low.
Answer: Another factor, such as carbon dioxide or light, is now limiting.
Glasshouses and polythene tunnels raise temperature and allow extra carbon dioxide, increasing photosynthesis and yield. Fertilisers replace minerals. Pesticides act fast but harm other species and pests become resistant; biological control is specific but slow.
The interactive lesson includes the diagrams for this topic.
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