The purpose of treating poor soil with lime is to increase the quantity of

Analyze the question: Lime (calcium oxide, calcium hydroxide, or calcium carbonate) is added to soil. We need to identify which nutrient it increases or helps increase.

Concept: Liming does these things:

• It raises soil pH, which reduces acidity.
• It supplies calcium.
• It encourages the activity of nitrogen-fixing and nitrifying bacteria, which work best in near-neutral soil, so the soil gains usable nitrogen (nitrates).
• It improves soil structure by flocculating clay.

Step by step:

1. Option C, carbohydrates, is made by plants through photosynthesis, not by the soil, so it is out.
2. Option B, phosphorus: acid soils tend to fix phosphorus, and liming can make it more available. It is not the main textbook reason, and lime does not add phosphorus.
3. Option D, sulphur: lime does not add sulphur, and it does not typically increase it.
4. Option A, nitrogen: in acidic soils, nitrifying and nitrogen-fixing bacteria such as Rhizobium, Azotobacter and Nitrosomonas are inhibited. Lime neutralizes the acidity, so these bacteria thrive and increase the nitrogen available to plants.

Of the options given, nitrogen is the one that matches how the WASSCE question is usually answered.

Answer: A. nitrogen

Tip: Link "lime" to "pH correction → bacteria active → more nitrogen." For similar questions, remember that lime mainly corrects acidity and helps nitrogen-related bacterial activity, while fertilizers like NPK supply nutrients directly.