(i) Canals make the soil infertile because in canal irrigation, where water table is a few feet below the ground, the alkaline salts come to the surface, mix with the soil and make it unproductive.
(ii) Tubewell irrigation is quite expensive as it requires continuous supply of electricity.
(iii) Excessive accumulation of salts make the soils unsuitable for cultivation because when salt concentrations in the soil are high, the movement of water from the soil to the root is slowed down. When the salt concentrations in the soil are higher than inside the root cells, the soil will draw water from the root, and the plant will wilt and die. Hence, the soil becomes unsuitable for cultivation.