Which one of the following is the main form of degradation in irrigated areas?

Salinisation of soils

The correct answer is Option 3: Salinisation of soils

In irrigated areas, excessive irrigation and poor drainage often lead to the accumulation of salts in the soil, causing salinisation. This reduces soil fertility and agricultural productivity.

• Wind erosion – This mainly occurs in dry and arid regions where strong winds remove the top fertile layer of soil. It is not the primary form of degradation specifically associated with irrigated areas.
• Gully erosion – This occurs when running water cuts deep channels or gullies into the soil, usually in areas with heavy rainfall or improper land management. It is not the main degradation problem caused by irrigation. 

NCERT: "One of the serious problems that arises out of faulty strategy of irrigation and agricultural development is degradation of land resources. This is serious because it may lead to depletion of soil fertility. The situation is particularly alarming in irrigated areas. A large tract of agricultural land has lost its fertility due to alkalisation and salinisation of soils and waterlogging."