ALKALI SOILS 103 



deep in the direction of the surface slope and run the 

 water into these from the irrigation ditch. In either 

 case the water is allowed to soak in until the soil is 

 thoroughly wet. The surface is then cultivated so as to 

 check surface evaporation. In the last few years the 

 government and many private companies have spent mil- 

 lions of dollars in putting in irrigation plants. By tlrir 



IRRIGATION IN FURROWS. 



means thousands of acres of land which would otherwise 

 have been valueless for agriculture has been made ex- 

 ceedingly productive. 



47. Alkali Soils. In dry regions where the rainfall all 

 sinks into the ground and after remaining for a time rises 

 to the surface and is evaporated, large areas are found 

 upon which almost nothing can be made to grow even 

 when sufficient water is provided. Often in the dry sea- 

 son white or brown crusts appear scattered over the sur- 



