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



to find, on the other hand, that a similar state of dififusion existed 

 in the soils to which NaCl or Na2S04 had been added appeared 

 wholly inexplicable in the light of the prevailing conception of 

 these salts as agents capable of producing flocculation in the 

 soil colloids. However, this apparent contradiction of well- 

 established facts brought out by the field observations becomes 

 more intelligible as the accumulating data define more clearly the 

 conditions necessary to produce the remarkable effects observed. 

 Thus it has been demonstrated, not only in the field but also in 

 the laboratory, that ihe removal from the soil by water of NaCl 

 or NaoS04, together with the water-soluble products of their 

 chemical reaction with the soil constituents, either wholly or in 

 part, is the initial step in creating a condition favorable for the 

 diffusion of the soil colloids and possibly for the formation of 

 new colloidal matter. Therefore the net result of salt application 

 to and subsequent washing of a soil is to render the soil com- 

 paratively impervious and to injure seriously its physical con- 

 dition. The leaching out of added NaoCOg from the soil also 

 presents some interesting phenomena, which are discussed below. 



Although the alteration in the physical condition of the soil 

 was first observed by the writer as purely incidental to an investi- 

 gation primarily designed to ascertain the toxicity limits of the 

 common alkali salts for crop plants, yet it has proved, at least 

 in the case at hand, a most perplexing factor in the production 

 of crops. Our experience would lead us to believe that these 

 after-effects of salt treatments, which appear during the course 

 of leaching the salts from the soil, would have some application 

 to the management of alkali lands, and perhaps some significance 

 with respect to fertilizer treatments. However, the literature 

 on these subjects, with a few exceptions, seems quite devoid of 

 any pertinent reference to the possible importance in these 

 problems of the factor discussed above. 



A survey of the literature concerning soils reveals the chief 

 exceptions just mentioned in the following important contribu- 

 tions to this subject. Thus, a brief but significant chapter, 

 "Veranderung der Durchlassigkeit durch Auswaschen der 

 Salze, ' ' by Adolph I\Iayer.^ records a somewhat .sudden reduction 



1 Forschungen auf dem Gebiete der Agrikultur-Phvsik, vol. 2, 1879, p. 251. 



