266 



FARM DEVELOPMENT 



Alkaline soils under irrigation must be handled with 

 special care. In many drouthy regions the alkaline 

 soils become still more alkaline when irrigated. This 

 may be due to the water used bringing, in solution, 



large portions of 

 the alkaline compounds 

 which, upon evapora- 

 tion, are left in the sur- 

 face soil. In other cases 

 it is due to the absorp- 

 tion of soluble alkaline 



Figure 166. Metal dam or tappoon. Compounds from the 



subsoil by the water, 



which upon rising to the surface and there evaporat- 

 ing leaves the surface soil with an increased 

 amount of these alkaline substances that are in- 

 jurious to plants. In yet other cases seepage water 

 from irrigated areas at higher levels absorb large quan- 

 tities of alkaline compounds and seeping forward through 

 porous underlayers, carry them to the surface on lower 

 areas where the alkaline salts are deposited upon the 

 evaporation of the water. In cases of this kind it some- 

 times happens that irrigation water applied to one farm 



Figures 167 and 168. Small boxes to conduct water from farm ditch into furrows. 



will thus flow underneath to another farm and injuriously 

 affect the neighbor's field. In many localities where 

 alkaline soils are irrigated, the conditions must be con- 

 stantly watched and special care taken not to use more 

 water than is necessary. In this way the fields which 



