CHEMICAL ANALYSIS OF SOILS 



317 



While it is supposed to measure the permanent fertility^ 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^ 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 ^ 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 op soil constituents insoluble in 



HQ, SP. GR. 1.115 



Soils 



Minnesota (Snyder) 



Fair Haven 



Holden 



Experiment Station . . . 

 Maryland (Veitch) 



Columbia 



Chesapeake 



Hudson Eiver Shale . . 



K20 



CaO 



MgO 



P.O. 



94 



25 



58 



40 



81 



61 



76 



45 



83 



41 



36 



18 



95 



90 



34 



66 



67 



82 



29 



15 



73 



37 



28 







SOs 



74 

 90 

 20 



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

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



* 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., TTie Chemical Composition of Maryland Soils; Md. 

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



