AN APPRAISAL OF POWER USED OS" FARMS 
23 
ililBli 
Fig. 23.— Soils originally 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 ashy 
gray in desert areas. The light-colored forest soils in the United States total about 800 million acres, 
the dark-colored grass-land soils about 600 million acres, and the light-colored arid soils about 500 mil- 
lion acres. (U. S. Dept. Agr. Yearbook 1921.) 
