80 



THE SMALL GRAINS 



There are three characteristics of this district : (1) ex- 

 treme aridity often necessitating irrigation, (2) the low 

 humus content of the soil, and (3) the abundance of 

 alkali usually present. These conditions are closely in- 

 terrelated and mutually dependent upon one another. 

 The absence of humus is a natural result of the re- 

 duction of the rainfall, upon which depends the existence 

 of plant life. Rainfall also tends to equalize the dis- 

 tribution of the alkaline substances of the soil, which 



FIG. 25. Field of Koffoid wheat near Nephi, Utah. 



in this district, however, are concentrated, in places, 

 in high percentages. The practice of over irrigation is 

 often allowed to make conditions worse by a deposit of 

 alkali largely above that which was already present. 

 Wheat does better in soil that is alkaline rather than 

 acid in reaction, but an excess of alkali becomes very 

 injurious. Rust on wheat is rare and in some localities 

 entirely unknown. Smut, however, is present to a great 

 extent. Stiffness of the straw and absence of rain prevent 



