May IS, 191S 



Soil Moisture and Soluble Salts 



191 



of the manure-extract solution, however, there was a marked decrease in 

 the surface tension, but this change evidently exerted no apparent effect 

 upon the moisture content of the soils treated with the manure-extract 

 solution, for these soils showed an increase in the moisture movement 

 rather than a decrease, which would have resulted from any noticeable 

 action of a decreased surface tension. 



The fact that the treatments which influenced to any extent soil- 

 moisture content or movement are those known to have a marked in- 

 fluence on the physical structure of soils points very strongly to the 

 conclusion that herein lies the effect of the salts in this regard. Some 

 information as to the effect of the treatments on the physical structure 

 of the soils in this experiment was obtained by the following work. At 

 the close of the moisture work the soil columns were removed from the 

 tubes and allowed to air-dry. Those found to be intact were selected 

 and equal lengths of the columns, 2)4 inches, were removed from their 

 lower ends. The resistance of these sections to a crushing force was 

 determined. The results are shown in Table III. 



Table III. — Resistance of sectioiis of the soil columns to a crushing force 



SANDY LOAM 



CLAY LOAM 



NajCOs. .. 

 NaNOg... 



NaCl 



Check.... 

 (NHJ^SO, 



CaHPOi 



CaCOa . . 

 KCl . . . 



K2SO4. . 



74.90 



68.68 

 67.88 



67.56 



A comparison of the order of treatments here with that in Table II, 

 in which the effect of the treatments on moisture content or movement 

 is given, shows close correlation between the two. Treatments which 



