Soil is one of the most important non-renewable basic resources on the earth’s surface. The major soil groups of Tamil Nadu are:

1. Red soils, (62 per cent)
2. Black soils (12 per cent)
3. Laterite soils (3 per cent) and
4. Coastal soils (7 per cent)

The red soils are further classified as:

1. Red loamy (30 per cent)
2. Red sterile (6 per cent)
3. Red-sandy (6 per cent)
4. Thin red (2 per cent) and
5. Deep red loamy soils (8 per cent)

As per the USDA system of soil classification (Taxonomy), the soils of Tamil Nadu are classified in to Six orders viz ,

1. Entisols
2. Inceptisols
3. Alfisols
4. Mollisols
5. Ultisols and
6. Vertisols

About 50 per cent of the total area of Tamil Nadu state is occupied by Inceptisol, 30 per cent by Alfisols, 7 per cent by Vertisols, 6 per cent by Entisols, 01 per cent by ultisols and very negligible area by Mollisols.

• Entisols : Young river alluvium, sandy and eroded red and laterite soils.
• Inceptisols: Moderately deep red, laterite and black soils are included under Inceptisol.
• Alfisols : Deep red and laterite soils
• Ultisols : Highly weathered laterite soils
• Vertisols: Deep black cotton soils and old alluvial soils are classified under vertisol.