Plate 1. — Illustration of the effects of con- 

 tinuous fallowing or cropping on the ability of 

 representative Californian soils to support a crop 

 of barley. Also illustrates general nature of in- 

 stallations used in investigations of soil solution 

 phenomena. 



In foreground 13th successive annual crop of 

 barley cropped soils ("A" soils). 



In background 2nd successive annual crop of 

 barley following a 10-year fallow period ("B" 

 soils). Only part of tanks shown. (From BURD 

 and Martin, unpublished). 



