The correct option is Alluvial soil.
Explanation
Alluvial soils are depositional soils formed by the accumulation of sediments (silt, sand, and clay) transported by rivers. They constitute the most widespread and agriculturally significant soil group in India, covering approximately 40% of the total land area.
Detailed Analysis
- Alluvial Soil (Correct): The deltas of the Mahanadi, Godavari, Krishna, and Kaveri rivers are located on the Eastern Coastal Plains. These rivers carry vast quantities of sediments from their upper and middle courses and deposit them at their mouths. Consequently, the soil found in these deltaic regions is coastal alluvium, which is highly fertile and suitable for the cultivation of crops like rice and jute.
- Black Soil (Incorrect): Also known as Regur soil, this type is primarily found in the Deccan Trap region (Maharashtra, Gujarat, and parts of Madhya Pradesh). It is formed from the weathering of basaltic lava rocks, not through deltaic deposition.
- Red Soil (Incorrect): This soil develops on crystalline igneous rocks in areas of low rainfall. It occupies large parts of the Deccan Plateau (Tamil Nadu, Karnataka, Andhra Pradesh, and Odisha) surrounding the black soil region but is distinct from the deep alluvial deposits of the river deltas.
- Laterite Soil (Incorrect): Laterite soils develop in areas with high temperatures and heavy rainfall due to intense leaching. They are typically found in the Western Ghats, parts of Odisha, and the North-Eastern states, rather than in the river deltas.
Key Takeaway: The deltas of the East Coast rivers (Mahanadi, Godavari, Krishna, and Kaveri) are composed of fertile Alluvial soil formed by the deposition of riverine sediments.