CHEMICAL COMPOSITION OF THE SOIL 173 



Interpretation of Partial Soil Analyses. The chemical analysis 

 of a soil must be considered in connection with a knowledge of its 

 location, depth, drainage conditions, permeability to water and 

 air, and, if possible, the amount of crops it produces. Without 

 consideration of the other factors which influence the fertility of 

 a soil, the chemical analysis may not lead to satisfactory con- 

 clusions. We must also remember that the same general type of 

 soil varies somewhat in composition, physical properties, and pro- 

 ductiveness within a given area, and also that different methods 

 of farming may cause considerable differences in soils originally 

 the same. 



The interpretation of a chemical analysis unaccompanied by 

 knowledge of the other soil conditions which affect its fertility, 

 may be unsatisfactory in a large proportion of cases. A careful 

 interpretation of results with the aid of the knowledge referred to 

 may sometimes be disappointing, but it is more often correct. 

 Analyses of miscellaneous samples of soils is also of less value 

 than systematic studies of definite areas. Analyses of virgin 

 soils, or soils which have not been long under cultivation, or not 

 treated with fertilizers, are more likely to yield a satisfactory 

 interpretation than analyses of soils whose properties have been 

 modified by long continued cultivation, or by applications of 

 fertilizers. It cannot be expected that chemical analysis of soils 

 will always give a satisfactory interpretation ; there will be 

 exceptions which may be difficult to understand until the scope of 

 our information has been widened. 



Chemical analysis of a soil with strong acids, together with 

 other information concerning the soil, should aid us in applying 

 the results secured by field experiments in one locality on a given 

 type of soil, to other localities and to other types of soil. It is 

 well known that the results of field experiments with fertilizers 

 are applicable only to the same types of soils under similar con- 

 ditions and with similar chemical composition, and may, or may 

 not, be applicable to other types of soils. Chemical analysis, and 

 the other information referred to, should aid us in applying 

 knowledge secured by field experiments and by experience, to the 



