Use chemical fertilisers to improve yields
Chemical fertilisers supply mineral ions that can support crop growth and improve yield when the required nutrients are limiting.
Core and Extended; Biology 0610, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked
Before you begin
- Know that crop and livestock production depend on both management and environmental conditions.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What can chemical fertilisers provide to crops?
What you will learn
- Explain how chemical fertilisers can support crop growth and yield
- Interpret a yield comparison without assuming unlimited benefit
Supply mineral nutrients to crops
Chemical fertilisers provide mineral ions to plants. For example, nitrate ions are needed to make amino acids and proteins, and magnesium ions are needed to make chlorophyll. When a required mineral nutrient limits growth, supplying it can increase crop growth and yield.
A fertiliser does not supply every condition needed for growth. Light, water, temperature, soil and other nutrients may limit production. If a nutrient is already sufficient, adding more does not guarantee another increase in yield.
Match yield claims to comparisons
A controlled comparison can show a difference between plots with and without a fertiliser under the tested conditions. To attribute the difference to the fertiliser, other relevant conditions should be kept similar, measurements should use the same area and crop, and repeat observations can improve reliability.
A result for one crop and site is not automatically a universal response. Report the measured yield and conditions, then explain the conclusion within that evidence.
Pause and explain
A fertiliser increases yield in one trial. Which conclusion is best supported?
Worked example
Two equal plots of the same crop receive the same water and light. A fertilised plot produces 4.8 kg per m²; a comparison plot produces 3.9 kg per m². State a supported conclusion.
Show the worked solution
- The tested crop and area are comparable.
- The fertilised plot has the larger measured yield.
Answer Under the stated conditions, the fertilised plot yielded 0.9 kg per m² more. This supports a fertiliser effect in this comparison, but does not establish the response for every soil or crop.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Explain one way a chemical fertiliser can increase crop yield.
Give me a hint
Name a mineral nutrient and connect it with growth.
Compare my reasoning
- Nitrate ions can be used to make amino acids.
- More amino acids can support protein production and growth when nitrate was limiting.
A fertiliser can supply nitrate ions used to make amino acids and proteins. If nitrate was limiting, supplying it can support growth and increase yield.
Look for these in your work
- Mineral ion named
- Limiting condition qualified
A field yields 3.2 kg per m² without fertiliser and 4.0 kg per m² with fertiliser. Calculate the yield difference and give a careful conclusion.
Give me a hint
Subtract the lower yield from the higher yield.
Compare my reasoning
- 4.0 − 3.2 = 0.8 kg per m².
- Keep the conclusion to the tested comparison.
The difference is 0.8 kg per m². The fertiliser-treated area yielded more in this comparison; the figures do not prove that every crop or soil would respond the same way.
Look for these in your work
- Difference and unit correct
- Conclusion bounded
Why might adding more fertiliser fail to increase yield further?
Give me a hint
Consider other limiting conditions and nutrient sufficiency.
Compare my reasoning
- The nutrient may no longer be limiting.
- Water, light, temperature or another nutrient could limit growth.
If the nutrient is already sufficient, another factor such as water or light may limit growth, so additional fertiliser need not increase yield.
Look for these in your work
- Alternative limit explained
- No unlimited response claimed
Common mistakes
- Treating fertiliser as food made by a plant
- Claiming more fertiliser always means more yield
- Ignoring other conditions in a comparison
What can you explain now?
What can chemical fertilisers provide to crops?
Compare with the explanation
Mineral ions that support growth
Mineral nutrients are used in plant processes.
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Make it stick
Explain how chemical fertilisers can improve yields and name two reasons that more fertiliser may not always raise yield.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.