114 SOIL PHYSICS AND MANAGEMENT 







Classes, Types and Phases in Illinois. It may be of interest 

 to give the classes of soils and their limits, with some of the types 

 and their phases as used in the Illinois classification. In numbering 

 soil types a system somewhat similar to the Dewey library system 

 has been used, in which the whole numbers represent the sub- 

 provinces and types, and the decimals, the phases. To illustrate: 

 A soil has the number 726.5. The number 7 means that it occurs 

 in the lowan glaciation, the 26 that it is brown silt loam, and .5 

 that rock is found less than 30 inches below the surface. These 

 numbers are convenient for use upon the soil maps in numbering 

 small soil areas. 



Peats consisting of 35 per cent or more of organic matter sometimes 

 mixed with some sand, silt or clay. 



1. Deep peat with peat more than 30 inches in depth. It is best 



drained by open ditches because of the unequal settling of tile, 

 thus getting them out of line. 



2. Medium peat on clay with peat between 12 and 30 inches in depth. 



Tile drains are usually below the peat and therefore have a 

 good bed. 



2.1 Medium peat on clayey sand. 



2.2 Medium peat on sand. 



2.4 Medium peat on gravel. 



2.5 Medium peat on rock. 



2.6 Medium peat on marl. 



3. Shallow peat on clay with peat 6 to 12 inches deep. It may be 



plowed sufliciently deep to bring up some clay for supplying 

 potassium. 



3.1 Shallow peat on clayey sand. 



3.2 Shallow peat on sand. 



3.4 Shallow peat on gravel. 



3.5 Shallow peat on rock. 



3.6 Shallow peat on marl. 



Peaty loams consisting of 15 to 35 per cent of organic matter with 

 a large proportion of sand and very little silt or clay. 

 10. Peaty loam on clay. 



10.1 Peaty loam on clayey sand. 



10.2 Peaty loam on sand. 



10.4 Peaty loam on gravel. 



10.5 Peaty loam on rock. 



Mucks 15 to 35 per cent of decomposed organic matter mixed with 

 much clay and silt. 

 13. Muck on clay. 



13.1 Muck on clayey sand. 



13.2 Muck on sand. 

 13.5 Muck on rock. 



Clays soils with more than 25 per cent of clay, usually containing 

 much sift. 



15. Drab clay. 



15.1 Sandy drab clay. 



15.2 Gravelly drab clay. 



15.3 Drab clay on sand. 

 Ifi. <C,ray clay. 



