24 SOIL COMPOSITION, CLASSES AND TYPES 



"^^ Greenville " may be applied, that soil is specified as "Green- 

 ville loam/' 



Soils specified in this manner are called "types." Thus 

 "Dunkirk loam" and "Greenville loam" are the names of two 

 types of soil. 



Soil Type Defined. — ^A soil type may be defined as soil that has 

 similar characteristics regarding texture^ mode of forma- 

 tion, origin of material, color, natural drainage, organic matter, 

 and subsoil. 



Types may be Grouped into Series. — Soil types may be classi- 

 fied or arranged into groups called "series." This is possible 

 because two or more soil types may have the same general charac- 

 teristics regarding mode of formation, range of color, etc. For 

 example, we have the following types grouped into a series:^ 



Dunkirk sand 



Dunkirk j&ne sand 



Dunkirk sandy loam 



Dunkirk fine sandy loam 1 a ^n «^«:^ m, ,^i • i « '^» \ 

 Dunkirk loam f = A soil series. (Dunkirk series.) 



Dunkirk silt loam 

 Dimkirk clay loam 

 Dunkirk clay 



In a similar manner are derived Greenville series, Miami 

 series, Volusia series and many others. The soil types composing 

 a series differ mainly in texture and productive power. 



Soil Series Defined. — ^A soil series may be defined as a 

 group of soil types similar in all respects except in texture 

 and productiveness. 



Soil Classification in Soil Survey. — In soil survey and mapping, 

 type is the unit used in soil classification. Types having similar 

 general characteristics aside from texture are classified in series. 



To facilitate the correlation of soil types and series the United 

 States Bureau of Soils has divided the United States generally 

 into thirteen soil provinces and regions (Fig. 13). The types of 

 soil derived through glacial and wind actions are to be found largely 

 within the Glacial and Loessial province. Types of lake origin are 

 included in the Glacial Lake and River Terrace province. Types 

 of marine origin are to be found in the Atlantic and Gulf Coastal 

 Plains province, etc. 



^The word "series" may be used in both a singular and plural sense. 



