A dark, clayey, moisture-retentive soil of the Deccan, also called regur, formed from the weathering of basaltic lava (the Deccan Trap) and ideal for growing cotton.
- Formed by the weathering of basaltic (volcanic) rock of the Deccan Trap; found mainly in Maharashtra, Madhya Pradesh, Gujarat, and parts of Karnataka, Telangana, and Tamil Nadu.
- High clay content gives it great moisture-holding capacity; it swells when wet and develops deep cracks when dry, which helps natural aeration.
- Rich in lime, iron, magnesia, and alumina, but poor in nitrogen, phosphorus, and organic matter.
- Most suitable for cotton (hence the name), and also good for jowar, wheat, and oilseeds; well suited to dry farming because it retains moisture.
- Black colour is attributed to the presence of iron compounds and humus, not necessarily to high organic content.
The basalt-Deccan Trap origin, the cotton suitability, the swell-and-crack property, and the States where it occurs are recurring agriculture and soils facts.
Black soil (regur, from basalt, retains moisture, good for cotton) is different from red soil (from crystalline rock, reddish from iron) and alluvial soil (river-deposited, most fertile and widespread).
Clayey moisture-retentive Deccan soil from weathered basalt; ideal for cotton; swells wet, cracks dry.