14 



plied with bumus, iu others thin and poor. Throughout the greater 

 part of this region the subsoil is clayey, but in some localities, i^articu- 

 larly near the mountains, where the drift aud wash is great, it may be 

 (juite gravelly in nature. Over the entire region, outside of the moun- 

 tains and higher foothills, the soil is characterized by the presence of 

 a greater or less amount of alkali. In the well-drained soils of the 

 footliills, mesas, and rolling prairies the amount of alkali present is 

 usually small, but in the broad, flat valleys and level plains it is often 

 hirge — sometimes so great as to completely change the character of the 



vegetation. (See tig. 

 3.) The water from 

 rains and melting 

 snows passes over 

 and through the sur- 

 face soil and leaches 

 out the alkali, which 

 is carried to the 

 streams, lakes, and 

 ponds. Naturally, 

 much of this water is 

 gathered into low 

 places in the plains 

 and valleys, where 

 it is evaporated rap- 

 idly, leaving the al- 

 kali in the surround- 

 ing soil. In many 

 places the alkali has 

 been brought to the 

 surface in consider- 

 able ([uantitics as a 

 result of improper 

 irrigation. This is 

 especially likely to 

 occur if water is used 

 in large (piantities 

 and then allowed to 

 evaporate from the surface. This maybe avoided in a large degree by 

 frecpient and shallow cultivation after each application of water. Often 

 the water used in irrigating is heavily charged with alkali, which, added 

 to that already present in the soil, ultimately renders the latter unlit 

 for the successful growing of the ordinary farm crops. In pojjular par- 

 lance there are two kinds of "alkali'' lands — "black alkali'' and 

 "white alkali." The former owes its peculiarities to the jiresence of 

 salsoda (sodium carbonate) and the latter to tlie presence of (ilauber 

 salt (sodinm sulphate) and lOpsom salt (magnesium sulphate i. The 

 "black alkali" is much more injurious to vegetation than the "white 

 alkali," and fortunately is much less cominon in this region. 



4; 



'^i 



y. 



Tig. 3. — An ''.Mkali sjiot." sliowiiii; cliaiiu tcrislic greascwooil Vf;;e- 



tatioii. 



