Black soils, also known as Regur soils or Black Cotton soils, are characteristic of the Deccan Trap region of India. These soils are typically dark grey to black in color, highly fertile, and known for their excellent moisture-retentive capacity. They are formed from the weathering of basaltic rocks, which are volcanic in origin.

Distribution: The largest concentration of black soils is found in the Deccan Plateau, covering significant parts of:

1. Maharashtra: A vast majority of the state is covered by black soils.
2. Gujarat: Particularly the Saurashtra region and parts of the southern districts.
3. Madhya Pradesh: Especially the Malwa Plateau and parts of the Narmada Valley.
4. Karnataka: The northern districts of the state.
5. Andhra Pradesh and Telangana: Parts of the western and southern regions.
6. Tamil Nadu: Scattered patches in the southern districts.

These soils are also found in smaller pockets in parts of Rajasthan and Uttar Pradesh. The typical topography of these regions is undulating, with plateaus and river valleys.

Specific Use for Agriculture: Black soils are highly valued for agriculture due to their unique properties:

1. High Moisture Retention: They are clayey in nature and have a high capacity to retain moisture, making them ideal for rain-fed crops, especially during dry spells. This property allows crops to sustain themselves even with limited rainfall.
2. Rich in Nutrients: They are rich in lime, iron, magnesia, and alumina, and also contain potash. However, they are generally poor in phosphorus, nitrogen, and organic matter.
3. Self-Ploughing Property: During dry periods, these soils develop deep cracks, which helps in aeration and natural tillage, often referred to as 'self-ploughing'.
4. Ideal for Cotton Cultivation: Their moisture-retentive capacity and fertility make them exceptionally well-suited for growing cotton, hence the name 'Black Cotton Soil'. India is a major cotton producer, largely owing to these soils.
5. Other Crops: Besides cotton, black soils are also extensively used for cultivating other important crops such as sugarcane, wheat, jowar (sorghum), tobacco, oilseeds (like groundnut and sunflower), and citrus fruits. The specific crop grown depends on the local climate and irrigation facilities.

Despite their fertility, black soils can be challenging to work with when wet, as they become sticky and difficult to till. However, their inherent characteristics make them a cornerstone of agricultural productivity in peninsular India.