Explain how using crop rotation can help improve food security.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Farmers in the UK often grow different crops in the same field each year in a repeating cycle. One common rotation involves growing a cereal crop such as wheat, followed by a legume crop such as clover or beans.
Model answer (4 marks)
Crop rotation replenishes nutrients in the soil. When a cereal crop such as wheat is grown it consumes large amounts of nitrates and other nutrients, leaving the soil depleted. The next year a legume crop such as clover or beans is planted. Legumes host nitrogen‑fixing bacteria in root nodules that convert atmospheric nitrogen into nitrogen‑containing compounds, adding nitrogen back to the soil. With more nutrients available, the following cereal crop can grow more vigorously and produce a higher yield. Higher yields mean more food is produced, so more people can be fed, which improves food security.
Examiner tips
- Use the word ‘replenishes’ and mention nitrogen‑fixing bacteria; link nutrient increase to higher yields; finish with the impact on food security.
- Show a clear causal chain: rotation → nutrient replenishment → higher yield → more food availability.
Common mistakes
- Failing to mention nitrogen‑fixing bacteria or the role of legumes; confusing the order of crops; not linking higher yields to improved food security.
Mark scheme (4 marks)
- Crop rotation replenishes nutrients (e.g. nitrates/nitrogen compounds) in the soil
- Legumes/nitrogen-fixing bacteria in root nodules convert atmospheric nitrogen into nitrogen-containing compounds in the soil
- Greater crop yields are produced because plants have access to more nutrients/nitrates for growth
- Greater food availability/higher yields mean more people can be fed, improving food security
Key terms in this question
Related
- All Edexcel GCSE Biology (1BI0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →