Life in the Soil 125 



These solutions were to be used to sprinkle the seed down, 

 and thus to convey the bacteria to the soil when the seed 

 are sown. Some years ago a similar preparation was sent 

 out from Germany under the name of "Nitragin," which 

 was to be applied to the soil to increase the number of the 

 nitrifying organisms concerned in the formation of nitrates 

 from organic nitrogen. This nitragin was a complete 

 failure, and no better results have so far been obtained 

 from the nitro-cultures for the inoculation of the legumes. 

 The artificially grown bacteria do not seem to adapt them- 

 selves readily to the soil conditions, and the nitro-cultures 

 will soon be relegated to the same disuse that has over- 

 taken nitragin. 



How, then, shall we bring about the needed inoculation 

 of the soil for the growth of the various legumes? The 

 easiest way is to get some soil from a field where the par- 

 ticular legumes have thriven and made nodules, and scatter 

 this over the soil to be sown. This method has uniformly 

 been successful. It has been found that soil, in which 

 certain more or less related legumes have grown, will inoc- 

 ulate the soil for others. The plant generally known as 

 sweet clover, melilotus alba, which grows as a weed in 

 nearly all parts of the United States, has been found to 

 contain bacteria which will Hve on the roots of alfalfa. It 

 has also been found that the more nearly related plant, 

 burr clover, medicago denticulata, when sown in the 

 rough burr-Uke seeds, will carry the bacteria of alfalfa 

 with it; since alfalfa, medicago saliva, is a very near gen- 

 eric relative. Then it has been found that the bacteria, 

 which Hve on the roots of the garden pea, will also live on 

 the roots of the vetch, and that crimson clover seed sown 



