14 



Yearbook of the Department of Agriculture^ 1921. 



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I fill f I III 1^ 



Fig. 6. — Soils origiually or at present covered with forest are normally light colored, 

 and are likely to be less fertile than soils in regions of lower rainfall. Grassland soils, 

 in general, are dark colored, the humid prairie soils being commonly almost black and 

 highly fertile — the subhumid prairie soils, blackest of all — while the semiarid short- 

 grass plains soils are dark brown or chocolate colored, the color gradually fading to 

 medium brown in regions of lesser rainfall, and to light brown or even ashv grav in 

 desert areas. The light-colored forest soils in the United States total about 800 million 

 acres, the dark-colored grassland soils about 600 million acres, and the light-colored 

 and soils about 500 million acres. 



