SALINITY FACTOR 287 
When the irrigation water applied is high in sodium and the 
soil becomes partially saturated with sodium, the clay particles 
are highly dispersed and may move downward through the soil 
to lower levels. This results in an unfavorable soil structure in 
which the first few inches of the soil profile may be relatively 
coarse textured, but lower in the profile where the clay has 
accumulated, there is a dense layer that is frequently very low 
in permeability. When such soils are wet, they tend to “run”’ 
together; when dry, they form hard clods, with large cracks on the 
surface. 
In addition to the adverse effects of saline and high-sodium 
waters on soil characteristics, and the reduction in the intake of 
water by plant roots where the substrate becomes excessively 
saline, some salts are toxic to crop plants when they occur in 
soils in excess amounts. The ions which are most likely to cause 
toxic reactions are chloride, sodium, bicarbonate, and sulfate. 
Among the microelements, excess boron most frequently produces 
symptoms of injury. 
Since undesirable soil conditions develop and unfavorable 
crop responses are likely to occur when the quality of irrigation 
water is unsatisfactory, the question arises: under what conditions 
and to what extent can saline waters to be used to supplement 
available supplies in areas where water shortage is a major prob- 
lem? Time does not permit me to discuss in detail the major 
aspects of this question, but the following lines of approach to 
the solution of the problem are suggested for consideration. First, 
selection of suitable land for irrigation; second, use of proper 
water-management practices; and third, selection of salt-tolerant 
crops which are adapted to local climatic conditions. 
Information regarding the salinity and sodium status of the 
soil, its hydraulic conductivity or water-transmission properties, 
the texture of soil and character of substrata, water-table condi- 
tions, drainability, and the topography of the area is necessary 
in considering the possibilities of using water of poor quality. 
Preleaching is required if the soil is saline, and leaching plus 
amendments may be indicated if the soil is saline-alkali and non- 
gypsiferous. Drainage is essential to remove excess salts, to 
