soils of the grasslands, profiles have thick, dark A horizons and yellow- 

 ish or grayish faintly mottled B horizons. 



4. Well drained. — Water is removed from the soil readily hut 

 not rapidly. Well-drained soils are commonly intermediate in texture, 

 although soils of other textural classes may also be well drained. Among 

 the podzolic soils, well-drained soils are free of mottlings (except for 

 fossil gley), and horizons may be brownish, yellowish, grayish, or red- 

 dish. They may be mottled deep in the C horizon or below depths of 

 several feet. Among the dark-colored soils of the grasslands, well- 

 drained soils have thick, dark A horizons, reddish, brownish, or yel- 

 lowish B horizons, and C horizons that may or may not be mottled. 

 Well-drained soils commonly retain optimum amounts of moisture for 

 plant growth after rains or additions of irrigation water. This is the 

 characteristic drainage of modal representatives of the zonal great soil 

 groups. 



5. Somewhat excessively drained. Water is removed from the soil 

 rapidly. Some of the soils are lithosolic. Many of them have little 

 horizon differentiation and are sandy and very porous. Among podzolic 

 soils, somewhat excessively drained types are free of mottling through- 

 out the profile and are brown, yellow, gray, or red. Among the dark- 

 colored soils of the grasslands, many profiles have relatively thin A 

 horizons, brownish, yellowish, grayish, or reddish thin B liorizons, and 

 no mottlings within the solum. Only a narrow range of crops can l)e 

 grown on these soils, and the yields are usually low without irrigation. 



6. Excessively drained. Water is removed from the soil very 

 rapidly. Excessively drained soils are commonly Lithosols or lithosolic, 

 and may be steep, very porous, or both. Shallow soils on slopes may be 

 excessively drained. Among podzolic soils, excessively drained types 

 are commonly brownish, yellowish, grayish, or reddish in color and 

 free of mottlings throughout the profile. Among the dai-k-colored soils 

 of the grasslands, profiles commonly have thin A horizons (except for 

 sand types that may have thick ones). Enough precipitation is com- 

 monly lost from these soils to make them unsuitable for ordinary crop 

 production. 



28 



