EXPERIMENT STATION BULLETINS. 605 



The above hypothesis is supported by an overwhelmiug amount of evi- 

 dence and consequently it also appears to be valid. 



The percentage of moisture content at which solidification refuses to 

 lake place very readily is almost the same as that at which plants be- 

 gin to wilt. From this it becomes evident that the wilting coefficient of 

 soils can be determined by the freezing point method. 



In view of the great concentration of the soil solution at the wilting 

 coefficient, it seems logical to conclude that the wilting of plants, is 

 I>artly due also to the concentration of the soil solution. 



By means of the freezing point method the effect of application of 

 soluble salts and acids upon the concentration of the soil solution in the 

 soil was also studied. The results pertaining to the soluble salts show 

 that the different compounds employed have an entirely difiTerent effect 

 u])on the concentration of the solution of the diverse classes of soil. In 

 the case of the neutral salts the solution of the agricultural soils was in- 

 creased from 35 to 100% of their added strength, while in the case of 

 the phosphate salts only a very small portion of their concentra- 

 tion was added to the soil solution, amounting in the majority of cases 

 1o only 10%. All the salts including the phosphates behaved the same 

 ill regard to the artificial substances, the quartz sand, kaolin, burned 

 soils, etc., as they all increased the concentration of their solution to 

 about the same degree, 100%. The neutral salt solutions did not be- 

 liave uniformly in the different types of soil, some of the salts produced 

 the greatest increase in concentration in the sands and the smallest in 

 the claj'^s, while other salts caused about the same degree of concentra- 

 t ion in all the distinct types of soil. 



The different acids affected the concentration of the soil solution very 

 differently. Some of the acids augumented the concentration of the so- 

 lution of the agricultural soils from 50 to 70% of their added strength, 

 others about 130%, and still others only about 5%. 



The increase in concentration of the soil solution as produced by the 

 application of 1he salts and acids is due to the formation of new sub- 

 stances, the depression of the freezing point of which is as great, greater, 

 or less than that of the original substance. In the case of the artificial 

 substances such as quartz sand, kaolin, burned soils, etc., both the orig- 

 inal concentration and composition of the salt solutions remained pract- 

 tically unaltered. 



