Option (C) is the correct answer. The provided text explicitly states that the situation of land degradation is 'particularly alarming in irrigated areas' where a large tract of agricultural land has lost its fertility due to 'alkalisation and salinisation of soils and waterlogging.' Options (A) and (B) are incorrect because the text associates soil erosion by water and wind with 'rainfed areas in humid and semi-arid tropics' rather than irrigated areas.