IMPROVEMENT OF THE SOIL 5o 



little rainfall to wash out soluble salts, they gradually 

 accumulate, especially in those places where water 

 stands and evaporates so that a thick alkaline in- 

 crustation is often formed on the surface. The 

 alternate soaking and surface drying of the soil 

 tends to pump up the soluble salts from the subsoil 

 and concentrate them near the surface. Even where 

 the water used is in itself free from alkali, continued 

 careless irrigation will, in many parts of the West, so 

 bring the salts to the surface as to prevent the pro- 

 duction of crops. Thousands of acres of valuable 

 lands have already been ruined in this way. An 

 absolute remedy for this trouble is, however, to be 

 found in proper drainage. A system of under- 

 drainage, wliich will carry off the surplus water from 

 below instead of allowing it to evaporate from the 

 surface, will not only prevent the undue accumula- 

 tion of salts in the upper layers, but it will serve to 

 redeem lands that are naturallv too alkaline for cul- 

 tivation by washing down the alkali and carrying it 

 off in the drainage water. There are immense areas 

 of land in the West that are now absolutely worthless 

 on account of an excess of alkali that could be re- 

 deemed and made extremely fertile by a combination 

 of irrio^ation and underdrainaofe. Even without un- 

 derdrainage the digging of deep surface drains at 

 such places as will serve to quickly carry off the 

 surplus irrigation water from the bottom of the fields 

 instead of allowing it to stand and evaporate in the 

 low places will do much to obviate what is really a 

 very grave danger for the irrigation farmer in many 

 parts of the arid regions. In fact irrigation should 



