202 THE BOOK OF ALFALFA 



2. In soil that is deficient in fertilizers, such as potash, 

 phosphoric acid or lime. 



The activity of the bacteria in securing nitrogen from 

 the air and rendering it available to the legumes does not 

 do away v^ith the need for such fertilizing elements as 

 potash and phosphorus. 



3. It must also be remembered that inoculation does 

 not ''act like magic" ; it v^ill not overcome results due to 

 bad seed, improper preparation and cultivation of the 

 ground, and decidedly adverse conditions of weather and 

 climate. 



In the use of the cultures, also, failure is almost certain 

 where the directions are not carefully studied and intel- 

 ligently followed. 



SWEET CLOVER SOIL USED TO INOCULATE ALFALFA 

 FIELDS 



The discovery in Illinois that inoculation of the soil for 

 alfalfa was necessary in certain places and not in others 

 suggested the theory that bacteria living on some other, 

 probably native, plant were identical with the alfalfa bac- 

 teria. Investigations led to satisfactory evidence that this 

 was the case and that the native plant was the ordinary 

 Sweet clover {Melilotus alba). The illustration facing 

 page 231 shows the results of a series of pot culture ex- 

 periments made at the University of Illinois and reported 

 in Bulletin No. 94 by Prof. Cyril G. Hopkins. The four 

 photographs were made five, six, seven and eight weeks, 

 respectively, from the time of planting. Alfalfa seed 

 were planted in each of the five pots, in carefully prepared 

 soil practically free of combined nitrogen, and at the same 

 time four of the five pots were inoculated as follows : 



