GOO STATE BOARD OF AGRICULTURE. 



The above data reveal many facts of high interest and great funda- 

 mental importance. Tliey slioAV (1) that the IICl and HNO3 increased 

 the concentration of the soil solution to about the same degree in all 

 soils except in the quartz sand, tind the magnitude lies between GO and 

 70% for the majorit}' of the agricultural soils; (2) The HoSO^ increased 

 the concentration of the soil solution in the majority of the agricultural 

 soils only about half as much as did the HCl and HNO3. (3) The C2H2O4 

 caused very little if any increases in concentration in the agricultural 

 soils, except in the artificial substances. (4) The CsHsOt caused an 

 increase of over 50% in the agricultural soils and nearly 100% in the 

 artificial substances. (5) The HC2H3O2 produced an augmentation in 

 the strength of the soils solution of all the soils employed of over 100%. 

 In some cases the magnitude of increase is as great as 130%. These last 

 results are certainly remarkable for they signify that the concentration 

 of the soil solution is augmented above the total concentration of the 

 acid added. 



The question raised above — how is the increase in concentration of the 

 soil solution by the application of soluble salts brought about, and what 

 is the composition of the resulting solution — may be raised also in the 

 case of the acids just considered. 



To obtain an answer to the above question it is necessary to resort to 

 other means for the lowering of the freezing point unfortunately indi- 

 cates only concentration and tells nothing of the reactions that might 

 take place between the soil and the salt solutions or acids, or of the 

 composition of the resulting solution. 



In the study of absorption or fixation of salts by soils one of two 

 methods is generally employed: (1) either shake a certain amount of 

 soil with an excess amount of solution and analyze the supernatant 

 liquid, or (2) pass through a column of soil a salt solution and analyze 

 the percolate. These studies have shown that in the case of neutral 

 salts the amount of the base of the salt solution added is diminished and 

 an equivalent or nearly equivalent quantity of other bases is dissolved 

 into the solution. Thus, if a soil is treated with a solution of KCl the 

 amount of K in the resulting solution is diminished but is replaced al- 

 most by an equivalent quantity of other bases such as Ca, Mg, etc., while 

 the amount of CI remains practically unchanged. 



In explanation of this phenomenon two theories have been proposed. 

 One is based upon the chemical reaction between the soil and solution 

 with an exchange of bases; and, the other is based upon a physical 

 selective adsorption of the base of the salt with a resulting acid which 

 dissolves an equivalent amount of soil bases. In the first theory it is 

 assumed that a neutral salt reacts with the polysilicates of the soil with 

 the base becoming fixed, at least at the beginning, and an equivalent 

 quantitv of another base being replaced, thus: Al^ Fe^ Mg^ Na^Ca 

 (SiOg), (H20),+2 KC1 = A1^ Fe, Mg, Na, K^ (SiOg), (H20),+CaCl2. This 

 equation typifies the metathetical reaction that may take place be- 

 tw^een a neutral salt and the zeolitic compounds of the soil. The 

 CaCL or any other salt formed is supposed to be in solution. 



The fixation of the soluble phosphates is supposed to be accomplished 

 by the bases present in the soil such as iron, aluminum, calcium, etc. 

 The reaction which is different from the above is typified by the follow- 



