376 University of California Publications in Agricultural Sciences [Vol.3 



of Soils, and differs from its methods in a number of ways. Since the 

 soils of Illinois are of a much narrower range of variation than are 

 those of the whole of the United States, the system of classification 

 for the state need not be so elaborate. The soils are divided accord- 

 ingly as they have been glaciated or not, and if glaciated, in what glaci- 

 ation period. They are further divided according to color, topogra- 

 phy, and texture of soil and subsoil. 23 Correlation of the types of 

 soil mapped in the various areas, one of the greatest sources of criti- 

 cism of the Bureau of Soils survey methods, is more easily handled 

 in the Illinois work, since it is possible for the one in charge of the 

 work to pass personally, while in the field, upon all correlation and 

 the establishment of all new types. It is insisted that the field men 

 map accurately and in sufficient detail. This insures the accuracy of 

 the maps as regards the standards adopted, the information is specific, 

 and the local users of the maps are not misled. 24 In connection with 

 the field classification and mapping, pot and plot cultures are carried 

 on, not so much to test the relative fertility of the untreated soils, but 

 to determine the effects of the application of various sorts and quanti- 

 ties of fertilizers. Hopkins, 25 to show the differences in detail between 

 the U. S. Bureau of Soils mapping and that of the Illinois Experi- 

 ment Station, compares a U. S. Bureau survey of 1902 with a state 

 survey published in 1911. This is not entirely fair, because with the 

 increase of field knowledge of soils gained by them and the realiza- 

 tion of the need of representing the soils in more detail, a survey 

 made bv the Bureau in 1911 would almost certainlv show much more 

 detail and show it with greater accuracy than the maps made in the 

 early period of the work. This point may be strengthened by the 

 notes given below on the comparison of a portion of an early survey 

 made in southern California by the Bureau of Soils with a recent 

 survey of the same soils made by the Bureau and the University of 

 California working in cooperation. 



PLAN OF THE PRESENT STUDY 



The present study is an attempt to see if certain soil types mapped 

 as the same from different areas in the state of California, and judged 

 to be the same by the criteria used by the Bureau of Soils, are the 



23 Hopkins, Soil Fertility and Permanent Agriculture (Boston, Ginn, 1910), 

 pp. 54-57. 



24 Ibid., p. 115. 



25 Ibid., pp. 114-15. 



