84 SOILS AND FERTILIZERS 



The figures under i give the composition of the 

 particles, while under 2 are given the results calcu- 

 lated on the basis of the total amount of each element. 

 For example, the clay contains 1.47 per cent, of 

 potash, while 50.8 per cent, of the total potash of the 

 soil is in the clay particles. 



A soil may contain a comparatively low per cent, of 

 potash or phosphoric acid, mainly in the finer particles 

 and evenly distributed so that the crop is better 

 supplied with food than if more were present in 

 the larger particles, unevenly distributed. The dis- 

 tribution of the plant food in the soilhas not been so 

 extensively studied as the question of total plant food. 

 Sometimes in judging the character of a soil from a 

 chemical analysis, a soil fault, as lack of potash in the 

 surface soil, is corrected by a high per cent, of 

 the same element in the subsoil. The distribution of 

 plant food in both surface soil and subsoil, as well 

 as in the various grades of soil particles, is an im- 

 portant factor of fertility. 



92. Composition of Typical Soils. — A few exam- 

 ples are given, in tabular form, of the chemical compo- 

 sition of soils from different regions in the United States. 

 On account of variations in the same localities, the 

 figures represent the composition of only limited areas 

 of soils. There have been made in the United States 

 a large number of soil analyses, which as yet have not 

 been compiled nor studied in a systematic way. 





