70 DRY LAND FARMING 



which may come up near to the surface. In yet other 

 instances these soils are so impregnated with fine clay 

 particles that they lose much of their silty character and 

 assume more the character of a clay soil. If alkali is 

 present these soils may assume a gumbo character. True 

 silt soils are relatively rich in the elements of plant food 

 and are very easily tilled, but they frequently lose mois- 

 ture easily.by leaching, and they are much liable to wash. 



Silty soils, sometimes called alluvial soils, are found 

 to a much greater extent in the valleys that line the 

 streams than elsewhere. These valleys in western areas 

 are usually relatively large, hence the area embraced as 

 silt is quite considerable. These soils are also found in 

 areas of considerable size that were at one time the 

 beds of ancient lakes. 



The relative value of silt soils depends largely on 

 their composition. True silt soils that are also deep 

 and uniform in their composition are usually very rich. 

 This may also be true of soils that are less uniform in 

 composition and texture. As a rule they are also easily 

 tilled. But they, in very many instances, allow water 

 to pass down through them so easily that crops grown 

 on them in dry areas in the absence of irrigating waters 

 are much liable to be injured by drought. The author 

 has found it much more difficult to grow good crops on 

 these soils in dry years than on the average bench land 

 soil. When these soils were underlaid by gravel, even 

 some considerable distance below the surface, the loss 

 of moisture was increased. When the gravel came up 

 quite close to the surface good crops could not be ob- 

 tained, even in seasons that were reasonably moist, in 

 the absence of irrigation. When the gravels were mixed 

 with silt, the results were much less harmful, just as the 

 gravel subsoils on bench lands that come up near the 

 surface are much less harmful when they are mixed with 

 a goodly sprinkling of clay. The summer temperature 



