Explanation:

Deccan Trap

The Deccan Plateau is a large plateau in India, making up most of the southern part of the country.The thick dark soil (called regur) found here is suitable for cotton cultivation.
Black soil is made from lava-solidified rocks and is also called as ‘Black Cotton Soil’ or ‘Regur Soil’. The black colour of regur soil is due to its iron content, deriving from plutonic lava materials.