Farmers in Kenya add powdered limestone (calcium carbonate) to acidic soils to increase crop yield. Which statement best explains why this improves plant growth?

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Question

Farmers in Kenya add powdered limestone (calcium carbonate) to acidic soils to increase crop yield. Which statement best explains why this improves plant growth?

Accepted Answer

Limestone neutralises acids in the soil, raising pH to optimal levels. — Award 1 mark for neutralising acids and raising pH. Calcium carbonate reacts with acids in soil: CaCO₃ + 2H⁺ → Ca²⁺ + H₂O + CO₂, which increases pH to levels optimal for nutrient uptake. A is incorrect because plants obtain CO₂ from the atmosphere, not soil. C is incorrect because limestone does not release oxygen when it decomposes. D is incorrect because limestone does not contain nitrogen.

Answer

Limestone neutralises acids in the soil, raising pH to optimal levels.

Answer

Limestone provides nitrogen compounds for protein synthesis.

Answer

Limestone decomposes to release oxygen for root respiration.

Answer

Limestone provides carbon dioxide for photosynthesis.

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