Assertion (A): Black soils are suitable for cotton cultivation. Reason (R): They are rich in humus. Select the correct answer from the codes given below:

The correct answer is C: (A) is true, but (R) is false. Black soils (regur) are indeed well suited to cotton, and that is the standard NCERT Geography fact behind the assertion. The reason fails because black soils are not rich in humus. They are rich in lime, iron, magnesia, alumina and potash, but they are poor in nitrogen, phosphorus and organic matter. Their black colour comes mainly from iron compounds and titaniferous magnetite, not from humus.

The concept here is soil-crop matching under the Physical Geography and Indian Agriculture syllabus. Black soil's moisture-retaining capacity, its swelling and cracking when wet and dry, and its lime content together explain why it suits cotton in the Deccan Trap region of Maharashtra, Gujarat, Madhya Pradesh and Karnataka. For Mains, the same soil logic feeds into questions on dryland agriculture and fertiliser policy, since these soils need nitrogen and phosphorus inputs.

Trap: Candidates see the word "black" and assume organic richness, so they mark (R) as true and pick B or A. Check the chemistry of the soil, not just its colour.