SOIL AND SUBSOIL. 



155 



It is very important that the bacillus should be present in 

 the earliest stages of the growth of the seedlings ; otherwise the 

 latter will undergo a longer or shorter period of starvation, 

 unless the soil contains, or is furnished with, a sufficiency of 

 available nitrogen to supply their immediate wants. When 

 such a supply is very abundant, the legume crop will sometimes 

 develop no nodules at all ; but the best crops appear to be the 

 result of a thorough infection, and abundant formation of the 

 excrescences. 



Cultural Results. The marked results obtained in certain 

 soils by inoculation with the legume-root bacillus are exempli- 

 fied in the following table, showing results of experiments by 

 J. F. Duggar, at the Alabama Experiment station. 1 



TABLE SHOWING INCREASE OF PRODUCTION BY SOIL INOCULATION. 



Such marked increases from soil inocculation cannot of 

 course be expected in cases where the soil has previously borne 

 leguminous crops of similar nature and therefore already con- 

 tains the root bacteria. Hence Duggar found no increase of 

 production when inoculating for cowpea, land that had borne 

 that crop two years before and already contained the root bac- 

 teria. In the arid region, where the almost universally calcare- 

 ous soils usually bear a natural growth largely composed of 

 various leguminous plants, inoculation is likely to be less com- 

 monly effective than in the humid region east of the Missis- 

 sippi, where leguminous plants are much less generally present 

 in the native flora. 



The distinctive agricultural function of supplying nitrogen 

 to the soils on which they grow, renders inexcusable the per- 

 sistence of some writers and teachers in designating all forage 

 plants as " grasses." \Yhatever excuse there may have been 

 for this practice so long as the nitrogen-gathering function of 

 the legumes was unknown, disappears with this discovery, and 



iBull. Ala. Exp't Station, No. 96, 1898. 



