Regur soil refers to

Regur is the regional name for black cotton soil, a dark clayey soil ideal for growing cotton.

Laterite soil is a red, leached tropical soil, not regur.

Desert soil is sandy and low in moisture, unlike moisture-retentive regur.

Alluvial soil is river-deposited and distinct from this volcanic black soil.

Regur forms from the weathered basaltic lava of the Deccan Trap.

Its high clay content lets it swell when wet and crack when dry.