The scarcity of good quality irrigation water is a serious problem in arid and semiarid zones of the world which comprise one third of the earth. Fresh water resources which are very scarce, forming only 3% of the total water reserves are overexploited and consequently have been tending to cause salinisation. Remaining 97% water in sea is excessively saline and generally not suitable for large scale exploitation in agriculture. More than half of the world's ground water supplies are also saline. Although, to cope with the increasing requirements of the accelerating population, irrigated area in the world in last two centuries has increased from 8 mha (1800) to 220 mha (1990), but development of salinity on about half the irrigated land, caused due to indiscriminate use of waters, has been a serious constraint for optimum crop production. In this context, the rational use of irrigation waters, without development of salinity, is the most important challenging task and herein lies the value of scientific knowledge on the use of saline water in agriculture.
