EXPERIMENT STATION BULLETINS. 



365 



INOCULATION WITH NODULE FORMING BACTERIA. 



Circular No. 5. 



EXPLANATION OF FIGURES : — Fig. 1. These two pea plants were grown in clean 

 quartz sand to which had been added small quantities of all the necessary elements of 

 plant food except nitrogen. The conditions were exactly identical except that plant A was 

 without root nodudes (see Fig. 2) and plant B had numerous nodules well developed (see 

 Figure 3. J 



Failure to obtain a good stand of alfalfa, or. any of the legumes, may 

 be due to the following factors : 



1. 



3. 

 3. 

 4. 

 5. 



Poor seed. 



Inadequate drainage. 

 Unsuitable soil. 

 Weed competition. 



Absence of iiodule-forniing bacteria. 



FIGURE 2. 



The Value of Nodules. — 



When the proper bacteria are present in the. soil, some plants, such 

 as alfalfa, clover, peas, beans, and other legumes develop nodules upon 

 their roots in which these bacteria live in enormous numbers. In these 

 nodules the free nitrogen of the air is so changed that these plants are 

 able to make use of it in their gTowth. At the Illinois station, it was 

 shown that 40 lbs. per acre of nitrogen might be added to a single 

 cutting of alfalfa in this way, a gain of more than six dollars per acre. 

 Beside this, a large amount of available nitrogen had been stored in 



