With reference to the soil types of India, consider the following assertions: Assertion (A): Regur soils or black cotton soils develop extensive deep cracks during dry hot seasons, exhibiting a natural self-ploughing property. Reason (R): Black soils contain high proportions of swelling clay minerals like montmorillonite that expand upon wetting and contract severely upon drying. Which of the following is correct?

💡 Solution & Explanation

Regur soils formed over Deccan basalt traps develop deep shrinkage cracks in summer, facilitating aeration and mixing known as self-ploughing. This structural behavior stems from the abundance of expanding clay minerals such as montmorillonite, which swell extensively upon moisture absorption and shrink during desiccation. These soils retain moisture remarkably well, making them ideal for rainfed cotton cultivation. Laterite soils, by contrast, form in regions of high temperature and heavy leaching.