Laterite soil develops mainly as a result of:

Leaching is the process in which heavy rainfall washes soluble nutrients, such as lime, silica, potash and other bases, out of the upper layers of the soil and carries them down into lower layers or away altogether.

Laterite soil forms in areas with high temperature and heavy rainfall, with alternating wet and dry seasons. The heavy rain causes intense leaching, removing silica and lime from the soil. What is left behind are oxides of iron and aluminium, which do not dissolve easily. The iron oxides give laterite soil its red or reddish-brown colour. The name "laterite" comes from the Latin word "later", meaning "brick", because laterite becomes very hard when exposed to air and is cut into blocks for building, as in Kerala and Goa.

Features of laterite soil:

• It is rich in iron and aluminium oxides.
• It is poor in nitrogen, phosphorus, potash, lime and organic matter, so it is generally less fertile and acidic.
• With heavy manuring and fertilisers, it can be used to grow crops such as tea, coffee, rubber, cashew, coconut and areca nut.

In India, laterite soils are found mainly on the summits of the Western Ghats, the Eastern Ghats, parts of Karnataka, Kerala, Tamil Nadu, Odisha, Madhya Pradesh, Assam and Meghalaya. They cover about 3.7% of the country's area. Bauxite, the ore of aluminium, is often found in laterite areas.

The National Bureau of Soil Survey and Land Use Planning (Nagpur) and the ICAR have classified Indian soils into eight major groups: alluvial, black, red and yellow, laterite, arid (desert), saline, peaty and forest soils.

Why not the other options?

• ✗Deposition by rivers forms alluvial soil.
• ✗Wind erosion and deposition form arid or desert soils.
• ✗Glacial action forms morainic deposits in mountain areas.