Q1. [4] medium exam-ready
Read the following passage and answer the questions that follow:
A soil scientist surveys a region in the Deccan plateau of Maharashtra. She observes that the soil is deep black in colour with an extremely fine texture and becomes very sticky after the first monsoon rains, making it hard to plough. During the long dry summer, the soil develops wide, deep cracks. Local farmers traditionally cultivate this soil just after the first shower or during the pre-monsoon period. She also notes the soil is rich in calcium carbonate, magnesium, potash and lime, but tests reveal it is deficient in one key nutrient. The region is famous for a particular commercial crop.
(i) Identify the type of soil described and name the parent rock responsible for its formation. (1)
(ii) Which nutrient is this soil generally deficient in? (1)
(iii) Name the commercial crop for which this soil is most suitable and give one reason why. (1)
(iv) How do the deep cracks that form in summer benefit the soil? (1)
Generated by claude-sonnet-4-6 · 2026-06-26 13:28 · grounding rag
Model Answer
(i) The soil described is Black Soil (Regur soil). It is formed from the Deccan Trap Basalt (lava flows), which is the parent rock responsible for its formation.
(ii) Black soil is generally deficient in phosphoric content (phosphorus).
(iii) Black soil is most suitable for growing cotton (hence called black cotton soil). It is suitable because it has high moisture-retaining capacity, which is ideal for the long growing period of cotton.
(iv) The deep cracks that develop during hot, dry summer help in the proper aeration of the soil, allowing air to circulate through the lower layers and improving soil health.
Source: Resources and Development, Classification of Soils — Black Soil
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Explanation
- (i) Always name both — the soil type AND its parent rock. Examiners award separate marks for each part in a 1-mark question only if it has one clear answer; here both names together form the complete answer.
- (ii) The textbook specifically states black soil is "generally poor in phosphoric contents." Write "phosphoric content" or "phosphorus" — both are accepted.
- (iii) Mention both the crop name and the reason. Cotton + moisture retention = full mark.
- (iv) The textbook directly states cracks "help in the proper aeration of the soil." Use this exact language; do not invent additional benefits.