624 STATE BOARD OF AGRICULTURE. 



which would be detrimental to the growth of plants. Through the ab- 

 sorption-adsorption phenomena, salts are given up to the soil solution 

 when the latter becomes dilute, or salts are withdrawn from it when it 

 becomes concentrated and thus a constant equilibrium is maintained. 



Since it was found that by means of the freezing point method the 

 concentration of the soil solution can be measured directly in the soil, 

 it was at once suggested that this method might be used to study directly 

 the effect of application of soluble salts upon the concentration of the 

 soil solution in the soil. The results thus directly obtained ought to 

 show definitely whether or not the concentration of the soil solution in 

 the soil can be increased by application of soluble salts. 



The procedure consisted of treating different types of soil with 

 n / 100 solution of various salts, allowing them to stand in room tem- 

 perature and saturated atmosphere for about 24 hours, and then deter- 

 mining the lowering of their freezing point. To each soil sample was 

 added a sufficient amount of a solution to bring it up to a very high 

 moisture content, thus eliminating some of the errors that occur at the 

 low moisture content. For each treated sample there was always a 

 check having the same percentage of moislure, but made up only of 

 water. Great care was taken to mix each soil sample with the solution 

 or water, very thoroughly. The results obtained are detailed in table 11, 



Tahle 11. Effect of Application of SoluMe Salts upon the Concentration of the Soil Solution 



in the Soih 



Before entering into the discussion of the foregoing data, an explana- 

 tion as to their form of presentation is necessary. The first column 

 to the left of each salt solution contains the loAvering of the freezing 

 point of the solution itself; the second column contains the lowering 

 of the freezing point of soil treated with the solution, and, this lower- 

 ing is entirely due to the solution applied, as the amount of depression 

 due to the soil itself at that moisture content has been subtracted ; the 

 third column shows the difference in the depression of the solution be- 

 fore and after it is added to the soil ; the fourth column contains the 

 percentage of change in the depression that the salt solution suffered 

 in the soil; and, the fifth column shows Avhat percentage of the original 

 concentration of the salt solution went to increase the concentration of 

 the soil solution. 



With this explanation, the above data showing the influence of ap- 

 plication of soluble salts upon the concentration of the soil solution in 

 the soil may. now be considered. An examination of the figures in the 

 fifth column of the various salt solutions shows many remarkable 

 facts. Starting with the KCl solution it will be seen that from 70.81 

 to 100% of the concentration of the salt solution went to concentrate 

 the soil solution. The concentration of the soil solution is increased 

 greatest in quartz sand, kaolin, sandy loam, and peat, and least in 

 humus loam. 



Considering next the KoSO^ solution it will be seen that a much 

 smaller percentage of the concentration of this salt solution went to 

 increase the concentration of the soil solution of the various soils. 

 With the exception of quartz sand and kaolin, where the increase Is 



