EXPERIMENT STATION BULLETINS. 



857 



Evidently, therefore, the application of soluble salts increases the lime 

 requirements of soils quite markedly. The question now is, is this in- 

 crease permanent or only temporary, and in either case how is it brought 

 about? 



To procure information upon these questions the following line of 

 research was pursued : To 20 grams of soil were added 20 c. c. of any one 

 of the salt solutions. The ratio of the soil to the solution and the 

 strength of the solution were the same as above. The mixture was stirred 

 and allowed to stand for about an hour. Then the mixture was poured 

 upon a filter paper in a funnel and washed with water. The soil was 

 allowed to dry in room temperature and its lime requirement was de- 

 termined in the usual manner. The results obtained are detailed in 

 Table 12. 



TABLE 12. LIME REQUIREMENT -QF SOILS WHICH WERE TREATED WITH SALT 



SOLUTIONS AND THEN WASHED. 



The data in the above table are highly interesting and very significant. 

 They show that the soils which were treated with various salt solutions 

 and then washed, have practically the* same lime requirement as that 

 before treatment. In other words, the substance which increases their 

 lime requirement when they are treated with the soluble salts disappears 

 upon washing, and they come back to their original lime requirement. 



These data tJien go to prove three main facts ^ (1) The substance which 

 caused an increase in the lime requirement of the soil upon being treated 

 with the soluble salts was soluble or i7i solution and was readily carried 

 away by ivashing, (2) The treatment did not produce any permanent 

 change in the soil, either chemical or physical and consequently (3) the 

 increase in lime requirement brought about by the application of soluble 

 salts teas only temporary and not permanent. 



Now what is the nature of the substance which is produced in the soil 

 by the salts, and is readily soluble or in solution, that causes the in- 

 crease in the lime requirement. Before attempting to answer this ques- 

 tion it is essential to consider first the type of curve that the soils con- 

 taining the substance, i. e., the soils which are treated with the salt solu- 

 tion and not washed, will yield upon being titrated with CalOH), 

 according to the freezing point method. The data pertaining to this 

 phase of the investigation are contained in Table 13 and graphically 

 represented in figures 7a, 7b, 7c and 7d. Only a few typical examples 

 are here submitted. 



