092 STATE BOARD OF AGRICULTURE. 



In the second place the preceding experimental data show that the 

 extent of solubility is very considerable in all the salt treatments and 

 in all of the soils, with few exceptions. All the soils, except sand, 

 treated with NaNO, KNO„ KCL K.SO,, (NHJ^SO^, MgSO,, and 

 XaO^H.p^ yielded quite a large amount of material to solution by the 

 end of the experiment. Thus, the depression of many of these salts rose 

 from about .005° to about .110°C or from 125 to 2750 parts per million. 

 Tlie only salt treatments which rlid not cause a large solubility product 

 were the CaCNO,).,, KH,PO^, and CaHJPOJ,. The depression in some 

 of these salt treatments rose only from about .007° to 015C or from 175 

 to 375 parts per million of solution. Considering the solubility products 

 of each salt treatment and taking the check for basis of comparison it is 

 evident that the amount of material that goes into solution varies con- 

 siderably l)etween the various salt treatments within any one soil, except 

 sand. As a rule NaNO,, and NaCr.HoOo treatments yielded the greatest 

 s(.lubilitv product, the CafNO,).,, KH.rO, and raHjrO,)., the smallest 

 and the KN()3, KCL, K,SO„ (^^HJ.SO, and MgSO^ an intermediate. 

 In man}' soils the CaH^CPO^)^ and in a few soils the Ca(N03)^ and 

 KHaPO^ treatments did not only give the smallest concentrations but 

 even a smaller concentration than the check. Evidently these salt treat- 

 ments tended to have an indifferent or depressing effect upon the solu- 

 bility of soils. Besides there being a difference in the extent of solu- 

 bility between the various salt treatments within the same soil there 

 is also a difference in the extent of solubility between the various soils 

 treated witli the same salt. Between the claj's, clay loams, silt loams and 

 sandy loams, this difference is not verj^ marked, but between these 

 classes of soil and sand the difference is very great. Indeed, the extent 

 of solubility of sand treated with the various salts is practically negligi- 

 ble. Thus, tlie dei)ressi()n rises only from 00:'° to .010°C as compared 

 to the depression of from .005° to .110° in some of the other soils. The 

 salt treatments of sand therefore, had practically no effect upon its 

 . solubility. 



The study on tlie rate and extent of solubilitv of soils treated with 

 salts and then washed until all their free soluble salts vv'cre eliminated 

 seems to prove quite conclusively the two general facts, (1) the rate of 

 solubility of the treated soils is comparatively very slow and gradual 

 and the process continues for a long time, but usually about 60 days, 

 and (2) the extent of solubility of these same soils is very considerable, 

 with few exceptions. 



Now it would be highly interesting and very important to know what 

 the chemical composition is of the material that goes into solution in 

 the different soils treated with the various salt solution. Unfortunately 

 tlie freezing point method does not itself yield any information upon 

 this point and consequently no definite statements can be made on it. 

 It may be stated, however, that this problem is now being investigated 

 by Spurway in this laboratory and he finds that the substances which 

 go into solution consist principally of the base radical of the salt added, 

 of aluminum, iron, calcium, magnesium, potassium, phosphorus, and 

 organic matter. The amount of the base radical of the salt added 

 always predominates, but tlie amount and presence of other constitu- 

 ents varies Avith the soil and salt added. 



