The white saline and alkaline crust called kallar or reh in the canal districts of Haryana is mainly caused by:

The correct answer is B, waterlogging and a rising water table under canal irrigation. Where canal water has been applied for decades without matching drainage, the water table creeps up towards the surface. Capillary action then draws water upward, it evaporates in the dry heat, and the dissolved salts it carried are left behind as the white crust of kallar or reh. Rohtak, Jhajjar and Sonipat show the problem most clearly, and the remedies are gypsum, subsurface drainage and salt-tolerant varieties.

Option A is wrong because fertiliser can harm soil health but is not the cause of this particular salt crust. Option C describes the separate problem of the sandy south-west, where loose bhur soil shifts and forms dunes; that is a physical loss of soil, not salinisation. Option D describes gully and sheet erosion on the Shivalik slopes, again a different problem with different remedies such as check dams and plantations. Keep the three apart: salt in the canal plain, sand in the south-west, erosion in the hills.