CONDITIONS AFFECTING LEGUME INOCULATION. 



75 



A quantit}^ of soil was obtained from Blue Hill, Me., where the 

 culture tried last year had shown no benefit with garden peas. One 

 portion of this soil was placed in ordinary greenhouse pots; a second 

 portion was thoroughl}^ mixed with pulverized lime at the rate of 1 ton 

 to the acre, approximateh^, and placed in similar pots, and inoculated 

 seed sown in half of each series. Of 15 plants unlimed, 10 were with- 

 out nodules, 5 having a single nodule each; of IT plants limed, 15 were 

 well noduled and 2 apparently free, but nodules were evident on close 

 examination. The uninoculated pots in the unlimed series had no 

 nodules; in the limed series there were onh^ a few scattering nodules, 

 the majority of the plants, 10 out of 18, being free. 



This experiment was repeated, the soil itself being inoculated with 

 the liquid culture, with results even more striking. Of IT plants 

 unlimed, 12 were without nodules, 5 having' a total of 8 nodules; of 16 

 plants limed, all were well noduled, having a total of 8T nodules. The 

 uninoculated pots in the unlimed series had no nodules; in the limed 

 series, 15 out of 17 plants had no nodules, the other two having a 

 single nodule each. 



The combination of liming and inoculation was again striking!}^ 

 shown with alfalfa grown in a poor sandy soil from Lanham, Md. 

 In this case it seems reasonable to assume that alfalfa bacteria of low 

 virility were present in the soil. Under the normal unfavorable soil 

 conditions the native bacteria were unable to produce inoculation, and 

 the virile ones from the pure culture, while able to inoculate the alfalfa 

 plants, could benefit them only slightly. In the limed soil, however, 

 the native bacteria were able to produce nodules in considerable 

 numbers and to be of moderate benefit to the plants. The pure cul- 

 tures of virile bacteria under similar conditions, however, caused more 

 than double the increase that ma}^ be ascribed to the native bacteria. 



The following table shows the relative virility of the two types of 

 alfalfa bacteria in soil from Lanham: 



Treatment. 



Number of Number of 

 plants, j nodules. 



Average 

 height. 



Average 



dry 

 weight. 



Lime: 



Inoculated.. . 



Uninoculated 

 No lime: 



Inoculated... 



Uninoculated 



Inches. 

 15.5 

 13 



Grams. 

 0.39 

 .15 



.09 

 .06 



Similar results were obtained with a large number of soils concern- 

 ing which unfavorable reports had been received regarding attempts 

 at inoculation with cultures furnished by the Department of Agri- 

 culture. Field observations on the nodule formation of various 

 legumes showed the efiectiveness of using lime or some other agent 



100— VIII 



