730 SOILS: PROPERTIES AND MANAGEMENT 



much wider intervals. In getting acquainted with new 

 types, more borings and detailed observations are neces- 

 sary than after the soil properties have become familiar 

 and can be more readily identified. Where the soil is 

 highly variable, much more frequent observations are 

 necessary than where it is more uniform. As the survey 

 proceeds the field man progresses from point to point, 

 along the highway and in the field, on foot or by convey- 

 ance as may be more convenient, extending his observa- 

 tions about half the distance to the next highway in order 

 that all the territory may be covered most conveniently. 

 Usually the trip is arranged in a circuit. All areas of soil 

 essentially alike in their properties and plant relations are 

 recognized as of the same soil type, and their position on 

 the map is represented by one of the colors. As the 

 observations proceed, a change in the character of the soil 

 may occur. When this change becomes of such char- 

 acter and importance as to cause difference in agricultural 

 relations and to be recognizable under the plan of classi- 

 fication outlined above, a new type is recognized. The 

 boundary line between the two types must be carefully 

 traced out by observation and by borings. As the work 

 proceeds ether types of soil may be recognized and the 

 boundaries are determined and represented on the map, 

 each type being indicated by a particular color or symbol. 

 A large number of types of soil ifiay be recognized in each 

 area surveyed. The character and relationships of these 

 must be studied carefully in order to decide how they 

 may be grouped in series and larger units. 



In practice it is usually better for the field party to 

 first make general observations over the area, in order 

 to recognize the main divisions of the soil that may later 

 require subdivision into types. To this end all available 



