296 University of California Publications in Agricultural Sciences [Vol. 1 



1913-1-i aud l'Jl-i-15 were accompanied with similar manifesta- 

 tions of the extreme retentiveness and imperviousness of the salt- 

 treated soils. 



As previously remarked, all of the check soils responded 

 readily to cultivation and excellent seed beds were easily pre- 

 pared, while the soils to which XaCl and NaoSO^ had been added 

 were in an unworkable condition. A crust, an inch or so in 

 thickness, formed as soon as the surface dried, and was so hard 

 that even heavy tools made Imt little impression on it. Just 

 below the crust the soil was far too wet for plant roots aud re- 

 sembled putty in consistency. Contrary to expectations, the 

 soils treated with Na^COg exhibited better cultivating qualities 

 than the soils receiving the other salts, but inferior to those 

 of the control soils. 



"With a view to obtaining further information concerning the 

 great dissimilarity between the control soils and the salt-treated 

 soils, it seemed wnse to examine some of the surface water stand- 

 ing in the cylinders as well as the soil in contact therewith. These 

 proved to contain but mere traces of any salts. Of next im- 

 portance a study of the vertical distribution of the salts in the 

 cylinders disclosed the fact that the first few inches of soil 

 contained relatively small quantities of the salts, the first foot 

 more, the second still more, and the third foot most salt. From 

 these results it was concluded that the addition of XaCl or NaoSO^ 

 to a soil and subsequently washing the added salt, or at least 

 part of it. from the soil with water, produces a high degree of 

 diffusion in the soil colloids. Moreover, this alteration in diffusion 

 Avas accompanied with proportional changes in the other physical 

 characteristics of the soil. These conclusions based on our field 

 experience were soon verified by laboratory experiments. 



Laboratory Experiments Reproducing Field Observations 



It has been found that the field conditions can be readily 

 reproduced in the laboratory. Thus a simple procedure, illustrat- 

 ing qualitatively the lessened percolation, is to place 10 grams or 

 more of soil in a filter paper in a funnel, adding thereto either 

 NaCl or NaoSO^ as a solid or iii a water solution, and then wash- 



