40 



SUCCESSFUL FARMING 



as influenced by presence of organic matter, their water-holding capacity 

 varies directly with the increase in fineness of texture, the sand having 

 the smallest water-holding capacity and the silty clays and clays the largest. 



In classifying soils in the field the soil expert determines the type by 

 the appearance and feel of the soil. He takes numerous samples which 

 are sent to the laboratory where they are subjected to a mechanical analysis 

 in order to verify his judgment and field classification. 



The accompanying map shows the extent and location of the several 

 soil provinces and regions in the United States. 



Crop Adaptation. — That certain soils under definite climatic conditions 

 are best adapted to certain plants is obvious to anyone who has studied 



Inspecting and Sampling the Soil. 



different soils under field conditions. The marked variation in the char- 

 acter of vegetation is often made use of in defining the boundaries of soil 

 types and soil series. Adaptation is also manifest in the behavior of 

 cultivated crops. Among our well-known crops tobacco is the most 

 susceptible to changes in character of soil, and we find that a specific 

 type of tobacco can be grown to perfection only on a certain type of soil, 

 while a very different type of tobacco demands an entirely different type 

 of soil for its satisfactory growth. The red soils of the Orangeburg series 

 in Texas will produce an excellent quality of tobacco, whereas the Norfolk 

 series with gray surface soil and yellow subsoil, occurring in the same 

 general locality, gives very unsatisfactory results with the same variety of 

 tobacco. This difference in the tobacco is not due to the texture of the 

 soil, since soil of the same texture can readily be selected in both of these 

 series. The most casual observer cannot fail to distinguish the difference 

 between the Norfolk and Orangeburg soils, as manifested chiefly in their 

 color. 



