620 



STATE BOARD OF AGRICULTURE. 



Tahle 12 Effect of Normal Solutions of KiH PO* and CaHt (POili Upon the Concentration of the 



Soil Solution of Red Clay 



The&e results show that by iiicreasing the concentration to n /I a 

 greater percentage of the concentration goes to increase the concentra- 

 tion of the soil solution of the clay than when n / 100 strength is used, 

 but the amount of increase, however, is small in comparison with the 

 strength (jf the salt solution used. 



This part of the investigation goes to show, therefore, that the differ- 

 ent compounds employed have an entirely different effect upon the con- 

 centration of the soil solution of the various types of soil. In the case 

 of the neutral salts the soil solution was increased from 20 to 100% 

 of their strength added, while in the case of the phosphate salts very 

 little if any of their concentration was imparted to the soil solution 

 of the agricultural soils. 



The contention of the two theories already mentioned that the con- 

 centration of the soil solution tends to remain constant and is in equili- 

 brium with the soil and that the application of soluble salts may not 

 increase this concentration, are not entirely confirmed or borne out by 

 the data of this investigation. The only compounds which do not 

 seem to cause an increase in the concentration of the soil solution 

 the phosphates, and that is only in certain soils. 



The question now is: How is this increase in concentration of 

 soil solution by the soluble salts brought about? And, what is 

 composition of the resulting soil solution? 



As already stated the lowering of the freezing ])oint indicates only 

 total concentration, and it tells nothing of the reactions that might take 

 place between the soil and Siolution, or of the composition of the result- 

 ing soil solution. To obtain an answer to the abo\'e question, or ques- 

 tions, therefore, it is necessary to resort to other means. 



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

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

 of soil with an excess amount of solution, and analyse the supernatant 

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

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

 neutral salts the amount of the base of the salt solution added is dimin- 

 ished and an equivalent or nearly equivalent amount of other bases are 

 dissolved in 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 by an almost equivalent amount 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 a chemical reaction between the soil and solution 



are 



the 

 the 



