SOIL DEFICIENCIES 



251 



were conducted upon permanent experiment plots of the Rhode 

 Island Station. Air slaked lime was applied in 1893 to two of the 

 plots at the rate of 5,400 pounds per acre, and 1,000 pounds in 1894, 

 and none since. Equal quantities of potash, phosphoric acid, and 

 nitrogen have been applied annually to each plot, and, since 1899. 

 sulphate of magnesia. Two of the plots receive nitrogen as sul- 

 phate of ammonia, and two as nitrate of soda. The tendency of 

 the two plots which receive sulphate of ammonia is to become 



Fig. 60. Bare spot in barley caused by acid soil. Woburn, England. 



acid, since removal of the nitrogen leaves sulphuric acid; while 

 the latter two plots tend to become basic, since the residue left 

 is soda. 



Equal numbers of plants were set out on each plot. A great 

 number of different crops have been grown at various times. A 

 few results are as follows : 



