Regur soil, also known as black soil, is most widespread in Maharashtra. This type of soil is commonly found in the Deccan Plateau region, which includes parts of Maharashtra, as well as other states such as Madhya Pradesh, Gujarat, and Karnataka. However, Maharashtra has the largest area covered by regur soil compared to other states.

- Definition of Regur Soil:
Regur soil is a type of soil that is characterized by its dark black color and high fertility. It is derived from volcanic basalt rocks and is rich in minerals such as iron, aluminum, calcium, magnesium, and potassium. The presence of these minerals makes regur soil highly fertile and suitable for agriculture.

- Factors Contributing to the Widespread Distribution in Maharashtra:
1. Geological Formation: The Deccan Plateau, where Maharashtra is located, is primarily made up of basalt rocks. The weathering and decomposition of these rocks over millions of years have contributed to the formation of regur soil. The geological composition of the region plays a significant role in the widespread distribution of this soil type.

2. Climate: Maharashtra has a tropical monsoon climate with distinct wet and dry seasons. This climate provides the necessary conditions for the formation and preservation of regur soil. The alternating periods of heavy rainfall and dry spells help in the leaching and accumulation of minerals, making the soil fertile.

3. Vegetation and Organic Matter: The natural vegetation in Maharashtra, such as grasslands and shrubs, contributes to the accumulation of organic matter in the soil. The decomposition of plant material adds nutrients and improves the soil structure, making it suitable for agriculture.

4. Agricultural Practices: The farmers in Maharashtra have traditionally practiced agriculture on regur soil. The long history of cultivation has led to the development of specific agricultural techniques and practices that are well-suited for this type of soil. The success and productivity of agriculture on regur soil have further encouraged its widespread use in the state.

In conclusion, regur soil, also known as black soil, is most widespread in Maharashtra. The geological formation, climate, vegetation, organic matter, and agricultural practices in the region contribute to the extensive distribution of this fertile soil type.