338 Universiiy of California Publications in Agricultural Sciences [Vol. 1 



Summary 



1. The Davis elay-loam soil to which surface applications of 

 solutions of NaCl, Na.SO^ and Na^CO.. had been made became 

 very impervious to water, difficult to cultivate, and manifested 

 the characteristics of a high degree of diffusion, although these 

 salts have been shown to exercise flocculating powers on sus- 

 pensions of this soil. 



2. The salt-treated soils referred to were in cylinders exposed 

 to natural conditions. 



3. Examination of the soils showed that the salts had moved 

 downward into the lower layers of soil and that only the surface 

 soil had been affected in the direction described. 



4. The deflocculated condition resulting from adding certain 

 salts to and subsequently washing them from soils can be repro- 

 duced in the laboratory. 



5. The defloccnlation of soils treated in the manner described 

 above is intimately associated with the leaching of the NaCl and 

 Na2S04 down into the lower layers of soil by water. In the case 

 of NaoCO.^ the leaching process is not so essential for the diffusion 

 of the soil colloids. 



6. The addition of NaCl, Na^SO^ and NaXOg to the Davis 

 soil when followed with applications of water was particularly 

 effective in diminishing the rate of percolation through the soil 

 so treated. 



7. NaCl and NaoSO^ in con.stant contact with the Davis soil 

 increased the rate of percolation, except when a comparatively 

 dilute solution of NaCl was slowly passed through the soil for a 

 considerable period of time. 



8. The Davis soil treated with NaCl, NaOH, NaoCO.^ and other 

 salts, followed by leaching with water, yields a suspension in 

 water containing approximately ten times as much solid matter 

 as the same soil washed with water only. A real diffusion in such 

 salt-treated soils seems evident. 



9. The soil once diffused by washing out added NaCl requires 

 considerably more salt to completely flocculate it, than does the 

 water-washed soil. I^ikewise the injured physical condition of 

 such soils is not readily repaired by a second addition of NaCl. 



