CHEMICAL ANALYSIS OF SOILS 



317 



While it is supposed to measure the permanent fertility 1 of 

 a soil, there is no reason to suppose that there is any rela- 

 tionship between the nutrients extracted by a strong acid 

 in the laboratory and the amounts of the same constituents 

 absorbed by crops over a period of fifty or one hundred years. 

 Moreover, productivity is not necessarily controlled by the 

 amounts of available nutrients in a soil. This further vitiates 

 the data obtained by such an analysis. 



Snyder 2 has analyzed a number of Minnesota soils by 

 means of digestion with strong hydrochloric acid, decompos- 

 ing the acid-insoluble residues by fusion and determining 

 their composition. Veitch 3 has analyzed certain Maryland 

 soils by the hydrochloric acid method and by means of com- 

 plete solution. A few examples are given below to show how 

 soils may vary in the solubility of their constituents in strong 

 hydrochloric acid: 



Table LXX 



PERCENTAGE OF SOIL CONSTITUENTS INSOLUBLE IN 

 HQ, SP. GR. 1.115 



Soils 



Minnesota (Snyder) 



Fair Haven 



Holden 



Experiment Station. . 

 Maryland (Veitch) 



Columbia 



Chesapeake 



Hudson River Shale. 



so 3 



74 

 90 

 20 



169. Digestion with dilute acids. — A great number of 

 different acids have been used in a dilute condition for ex- 



1 Fertility is used here in the sense of potential productivity, the 

 nutrients in the soil being considered as the controlling factor. 



2 Snyder, Harry, Soils; Minn. Agr. Exp. Sta., Bui. 41, p. 35, 1895. 



* Veitch, F. P., The Chemical Composition of Maryland Soils; Md. 

 Agr. Exp. Sta., Bui. 70, p. 103, 1901. 



