18 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1016, 



The soils on the roUiiifi; land and certain areas of smooth land were 

 well enough drained and well enough protected from amuial fires to 

 permit the development of a forest vegetation. This in turn pro- 

 moted the formation of light-colored soils. They are usually brown 

 to light brown or gray in color and their content of organic matter is 

 low. 



The soils developed under conditions of excessive moisture or 

 insufficient subsoil drainage did not favor the development of a forest 

 vegetation. Their native vegetation therefore consisted of grasses. 



Well-drained soils on areas of flat or smooth land lying adjacent to 

 or surrounded by areas of wet lands were influenced in the native vege- 

 tation they produced by the latter, possibly because of the frequent 

 fires on them, so that as a rule they produced a grass vegetation also. 

 The greater part of the flat or smooth land area, therefore, were prai- 

 ries in their native state and because of their grass vegetation they 

 are dark in color and contain a liigh percentage of organic matter. 



These soils are prairie soils, however, and not steppe soils. They 

 are treeless because of excessive moisture, or were controlled by 

 neighboring areas of that kind, and not because of deficient moisture 

 as in the case of steppe soils. They lack the high content of soluble 

 constituents or readily decomposable minerals usually present in 

 steppe soils, their loose powdery structure, their thick humus horizon, 

 and their black color. 



The soils of the county have l^een identified as members of 23 

 series differing from each other in source of material and character 

 and composition of the soil and subsoil. 



The Miami series embraces the weU-drained timbered lands, having 

 hght grayish brown surface soils and yellow or yellowish-brown sub- 

 soils with little or no mottling and rcstmg upon miweathered cal- 

 careous material at a depth of 2| to 3 feet. The series is represented 

 in this county by three types, the fine sandy loam, loam, and silt loam. 



The Crosby series differs from the Miami cliiefly in having a grayer 

 surface soil and a white or mottled light-gray and yellowish-brown, 

 compact clay subsoil. The surface is flat to very gently undulating, 

 and the natural drainage is deficient. Only the silt loam member is 

 recognized in Porter County, 



The surface soils of the Carrington series are dark brown, and the 

 subsoils are brown to yellowish brown, resting upon miweathered, 

 moderately calcareous till at 2| to 3 feet. These soils have a nearly 

 level to roUing topography and are naturally well drained. They are 

 derived from ice-laid deposits, and the areas have existed under 

 prairie conditions, where large quantities of organic matter accumu- 

 lated in the soil. The Carrington silt loam is mapped and is one of 

 the important types of the county. 



