No. 6. DEPARTMENT OF AGRICULTURE. 205 



past year. It is a subject which offers wide opportunities for start- 

 ling write-ups and rosy predictions; moreover, the whole subject of 

 bacteria is such a hazy conception in the layman's mind that it is 

 doubly easy to obtain an erroneous idea of the proper usefulness of 

 soil inoculating cultures. To begin with, let it be understood that 

 soil inoculation is not a process "to get something for nothing." It 

 is no scheme for "perpetual motion" in crop-production; it con- 

 templates no real revolution in agricultural methods and ideas. 



The bacteria w T e are to consider are really but a small part of the 

 soil bacteria, namely, the group which nature has adapted to infect 

 the roots of leguminous or "pod-forming" plants, thereby forming 

 protuberances called "nodules" or "nitrogen-knots." This latter 

 name is derived from their well recognized ability to supply the 

 plant with nitrogen derived from the air and it is this power which 

 accounts for the fact that soil which bears a clover crop is actually 

 enriched for the succeeding crop. This fact has been utilized to ad- 

 vantage since the earliest days of agriculture by including in the 

 crop rotation some of the pea-like plants for adding nitrogen to the 

 soil. 



It is only in comparatively recent years, however, that the precise 

 reason for this soil improving power of the legumes has been estab- 

 lished. The demonstration by experiment that legumes could be 

 made to grow normally in soils entirely lacking in nitrogen, provided 

 the nodule-forming bacteria were present, proved beyond doubt their 

 nitrogen-fixing power, and gave a sufficient reason for a further study 

 of these organisms. The importance of soil nitrogen need not be 

 urged in addressing such a body as this. As Prof. Bailey recently 

 said: "The quest of nitrogen has enlisted not only many of the wisest 

 men, but it has absorbed the attention of even the major part of 

 mankind; for, by far the greater number of men have lived on the 

 bounty of the soil and their accustomed work has been an effort to 

 maintain that bounty." 



Now the question may arise, "If these beneficial bacteria are al- 

 ready in the soil, why need we concern ourselves about them?" 

 Doubtless in many cultivated soils there is no need to take them into 

 consideration, except as we utilize them by occasionally sowing 

 legumes. But, unfortunately, there are many soils which are not 

 naturally stocked with these bacteria. The attempt to grow legumes 

 in such soils results in one of three things: 



(1) The crop sown either fails absolutely, or it 



(2) Makes a scanty growth the first year and only after repeated 

 sowings becomes established, or it 



(3) Grows (in fairly rich soil) without the aid of the bacteria 

 (that is, having no nodules) drawing its nitrogen entirely from the 



