290 STATE BOARD OF AGRICULTURE. 



that the reaction, between soils and salts seems to be chemical and not 

 physical. 



In view of the different residual effects that the different salts or fertil- 

 izers have upon the solubility of soils, and in view of many theoretical and 

 practical considerations it was concluded that the solubility factor cannot 

 be considered an absolute or reliable criterion for the state of fertility or 

 crop-producing power of soils. In general, however, it can be said that a 

 very heavily fertilized or extremely rich soil gives a greater solubility product 

 than an unfertilized or poor soil. 



Although the solubility attained a constancy at the end of about 60 days, 

 this constancy was not believed to be a true equilibrium, the solution not 

 being saturated when solubility apparently ceases. This seems to be demon- 

 strated by the fact that when different proportions of soil and water are 

 employed an apparent equilibrium is attained in all the ratios, while the 

 solubility product is not at all the same when the equilibrium is reached, 

 and does not become the same no matter how long the soil and water in 

 the different ratios are kept in contact. Furthermore, considering the char- 

 acter of the soil it is deemed extremely doubtful if true equilibrium can 

 ever be attained in the soil solution. The solubility process of the soil would 

 undoubtedly go on for a long time, probably almost indefinitely, in view 

 of the extremely slow rate of solubility, if some factors did not intervene. 



When different soils were treated with a combination of salts, including 

 Ca(N03)2, NaNOa, KNO3, KCl, K2SO4, (NH4)2S04, MgSO^, KH2FO4, CaH4 

 (P04)2 and NaC2H302, and washed and kept under the same conditions as 

 indicated above, their rate of solubility was also slow, but the extent of 

 solubility was very appreciable. The phosphates in this combination did 

 not depress the solubilitj^ very markedly, but when (NH4)2S04 and NaC2H302 

 were omitted the decrease became more marked. 



Experimental field soils from the IHinois, New York (Cornell), Rhode 

 Island, and Ohio Experiment Stations, which had been fertilized in the usual 

 way were washed and kept at a moisture content of 1 of soil to 0.7 of water 

 and at room temperature. Their rate of solubility was very slow but their 

 extent of solubility varied, being rather appreciable in some of them and 

 quite small in others, and the variation failing to bear any close relation to 

 to the previous fertilizer treatment. These results w^ere in general agree- 

 ment with those of the single salt treated soils. Even when these soils were 

 kept at an optimum moisture content and placed outdoors under natural 

 conditions, they failed to give a solubility product which bore a close re- 

 lation to the previous fertilizer treatment, the rate of solubility being very 

 slow and the extent of solubility quite appreciable but far smaller than that 



Soils'treated with HNO3, HCl, H2SO4, H3PO4, H2C2O4, HC2H3O2 and 

 CeHsOy, washed, maintained at a moisture content of 1 of soil to 0.7 of water 

 and kept at room temperature shawed a quiet rapid rate of solubility, 

 although the extent of solubility varied being very small in the case of the 

 inorganic acids, slightly higher with phosphoric acid, and quite appreciable 

 with the organic acids. 



In the untreated soils, which were washed, kept at room temperature, 

 and at a moisture content of 1 of soil to 0.7 of water, both the rate and ex- 

 tent of solubility varied considerably between the different soils, there being 

 no close and consistent relationships between the solubility factor and the 

 class of soil, the organic matter content and the fineness of particles. Prac- 

 tically the same results were obtained when an optimum moisture content 



