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



fully filled with the Davis clay loam to which chemically equiva- 

 lent salt solutions were added, much in the same manner as the 

 salt applications wei'e made to the cylinder soils. A constant 

 head of water was then carefully maintained in the tubes. The 

 downward movement of the water was observed from time to 

 time and is graphically portrayed in Figure 2. 



From the curves in it it is verj^ apparent that the influence of 

 these salt additions, accompanied by subsequent surface applica- 

 tions of water to the soil, has been to retard, markedly, the down- 

 ward movement of the water through the soil. In less than 33 

 hours the water had penetrated the entire 141/2 inches of soil in 

 the control tube, while at the end of 552 hours, under a constant 

 head of three inches, the maximum distance reached in any of 

 the salt-treated soils was 13% inches in the case of the soil 

 receiving NaCl, followed by 13^4 inches in the Na^COg soil, and 

 but 11 inches in the soil to which Na2S04 had been added. At 

 the expiration of 56 days no percolation had occurred, though 

 the entire soil columns were moist. The total absence of percola- 

 tion in the salt-treated soils was attributed to the growth of algae 

 in the tubes. 



To test further the points under consideration, a second series 

 w^as prepared to study the rates of percolation through Davis 

 clay loam to which salts had been added in various ways. The 

 results of this experiment are embodied in Table I. 



In the above experiment the chemically equivalent quantities 

 of salts were mixed uniformly with the dry soil before placing 

 the mixture in the paraffine-coated brass percolation tubes, except 

 in the case of Nos. 12, 13, and 14, through which salt solutions 

 were passed of a strength (calculated on the basis of a previously 

 determined water-holding power of the soil) to give compara- 

 tively equal quantities of salts with those soils receiving the dry 

 salts. A head of one to two inches was carefully maintained on 

 the soil in all the tubes throughout the experiment. 



The results recorded in the foregoing table fully corroborate 

 the field experience. Thus, the average rate of percolation of 

 the check soil was 1.59 cc. per hour, while that of the soil to 

 which NaCl has been added was reduced to .19 cc. per hour. The 

 percolation through the other two soils which received solid 



