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



That these earlier findings have a greater significance in 

 agricultural practice than was formerly attributed to them be- 

 comes very evident when the practical phase is attempted of 

 cropping the diffused, salt-treated, water-washed soils in our 

 cylinders. Heretofore, the residual effects left upon clays and 

 clay soils after salts have been washed from them have been 

 chiefly considered in connection with their application to the 

 ceramic industry, and have been largely omitted from considera- 

 tion by those dealing with soils. 



Since the striking soil behavior under discussion was first 

 observed by us, as above explained, in crop cylinder experiments, 

 it appears desirable to introduce here a brief description of thesii 

 experiments. 



The Cylinder Experiment on the Physiological Effects of 

 NaCl, NaoSOi and NaoCOg on Crop Plants 



The cylinders used in this experiment are of galvanized iron, 

 open at both ends, coated inside and out with asphaltum, and 

 are fourteen inches in diameter and five feet long. They were 

 placed, during September, 1913, in a clay loam soil at Davis. 

 California, by digging holes to the depth of five feet. During 

 the progress of digging the holes the soil from each foot was 

 carefully removed and set aside separately, thus permitting the 

 cylinders to be refilled with the soil layers in the same order as 

 they exist naturally. 



The soils within the cylinders were then supplied with vary- 

 ing percentages of the three sodium salts, NaCl, NaoSOj. and 

 NaoCOg. It seemed a difficult task to secure a satisfactory mixture 

 of the salts with the soil already in the cylinders, and it was 

 therefore deemed wise to apply the salts to the surface of the 

 soils b}^ means of a solution containing the weighed quantity 

 of salt in 8800 cc. of distilled water. Accordingly, each cylinder 

 received the same quantity of water, but of a different salt con- 

 centration. In addition to the salts some of the soils also re- 

 ceived other treatments which, together with the salt treatments, 

 are detailed in the following chart. The quantities of salts were 



