THE SOIL SURVEY 719 



quirements of soils, their crop relations, and their agri- 

 cultural value make necessary the determination of the 

 properties of the soil, that are chiefly responsible for those 

 differences, and their arrangement into an orderly scheme 

 of classification. The aim is to divide the land into 

 areas of approximately the same general character. This 

 volume is largely an exposition of those properties of soils 

 that make differences in their crop relations and manage- 

 ment. It is evident that differences are numerous and 

 varied, and that some have greater significance than 

 others. 



Soils may be classified from many different points of 

 view. The basis may be purely geological, purely physical, 

 or almost entirely chemical. Any one of these alone is 

 likely to be inadequate for the purposes of the agriculturist. 

 The viewpoint of the agricultural soil survey should be 

 such as to secure unity in the crop relations of each distinct 

 area of soil recognized. 



The system of classification in use must employ as a 

 basis some combination of the groups of properties enu- 

 merated above. The combination selected has differed 

 in different parts of the world, depending on the training 



Principal Soil Areas of Iowa. Iowa Agr., Exp. Sta., Bui. 82. 

 1905. 



Mooers, G. A. The Soils of Tennessee. Tennessee Agr. 

 Exp. Sta., Bui. 78. 1906. 



Sherman, C. W. The Indiana* Soil Survey. Dept. Geol. 

 and Natural Resources, 32d Ann. Rept., pp. 17-47. 1907. 



Hopkins, C. G., and Pettit, J. H. The Fertility *of Illinois 

 Soils. Illinois Agr. Exp. Sta., Bui. 123. 1908. 



Hall, A. D., and Russell, E. J. Report on the Agriculture 

 and Soils of Kent, Surrey, and Essex. Dept. Bd. Agr. and Fish- 

 eries. London. 1911. 



Kummel, A. B. Soil Surveys as Related to Geology. N. J. 

 Bd. Agr., 36th Ann. Rept., pp. 162-169. 1908. 



