336 



ROOT-NODULE BACTERIA 



about i6 per cent exists as primary amino nitrogen and 20 per cent as amid nitrogen. 

 The nitrogen of the nodule is rapidly transferred from the underground nodule to the 



TABLE II 

 Effect of Inoculation on the Nitrogen in Soy Beans 



UNINOCULATED 



INOCULATED 



seed and stems. Thus the activity of the bacteria results in the formation of a nitrogen 



supply for the plant. Figure 3 shows the effect of the bacteria on the growth of red 



clover on poor, sandy soil. 



Since nitrogen may be the 



element limiting plant 

 growth, it is to be expected 

 that the addition of the 

 proper bacteria to certain 

 leguminous plants will make 

 possible a profuse growth 

 and larger amounts of pro- 

 tein. Some examples of the 

 effect of the nodule bacteria 

 on the host plant are pre- 



Nitrogen 



TAKEN FROM 



Air 



None. 



Total 

 Nitrogen 



Crops 



\ 



Nitrogen 

 taken from 

 Soil 



\ 



WOA 



sentedinTable II.' Figure 4 

 is prepared from the results 

 of field tests of soy beans 

 grown with and without bac- 

 teria. Field tests with new 

 crops show that inoculation 

 of the seed with the nodule 

 bacteria has a double ad- 

 vantage to the farmer. There 

 is an increase in the protein 

 and often an increase in the 

 yield. Numerous analyses 

 have been made of alfalfa, 

 clover, peas, and soy beans 

 grown with and without 

 nodule bacteria, some of 

 which are given in Table III. The results are in accord with the general facts 

 brought out by field tests. Aside from the favorable effects of inoculation on nitro- 

 ' Fred, E. B.: ibid., p. 469. 1921. 



Fig. 4. — Source of nitrogen for inoculated and uninocu- 

 lated soy beans. Areas in black represent total nitrogen; shaded 

 areas represent nitrogen from air and from soil in pounds 

 per acre. 



