10 CIRCULAK NO. 113, BUREAU OF PLANT INDUSTRY. 



nodules upon other plants of the same species in different localities. 

 Owing to the fact that different legumes are constantly being intro- 

 duced into agricultural regions, the importance of being able to dis- 

 seminate the nodule-forming bacteria is obvious. For many types of 

 legumes this is desirable, not only from the standpoint of making the 

 crop a better nitrogen fixer and better soil renovator, but because for 

 most legumes the crop is actually larger when properly inoculated. 

 Pure-culture inoculation is less certain than inoculation by means of 

 soil from old, well-inoculated fields, though of course it is free from 

 the danger of introducing troublesome weed seeds or plant diseases. 



WORK OF THE BUREAU OF PLANT INDUSTRY. 



The Bureau of Plant Industry is carrying on field experiments to 



determine, if possible, what soil conditions are most favorable for the 



successful inoculation of leguminous crops by the use of pure cultures 



and also to determine under what conditions it is useless to attempt 



to inoculate certain of the legumes without some radical change in 



the method of fertilizing or cultivating these fields. To extend this 



experimental work as far as possible, the Department of Agriculture 



is willing to supply cultures in any reasonable quantity, requiring 



only the filling in of blank reports which are occasionally forwarded 



for this purpose. 



CONCLUSION. 



A casual review of the present status of soil bacteriology shows that 

 it is a subject of almost bewildering complexity, but very intimately 

 associated with the normal physiology of all crop plants. By learning 

 what functions must be performed in the soil and by studying each 

 group of organisms that has a measurable function, we believe that 

 we can learn how to enhance the desirable activities of thaliving soil 

 and to check the undesirable ones. We may never find another rela- 

 tionship so simple as that existing between the legume crop and the 

 nodule bacillus or one which we can control so simply from a central 

 laboratory; but surely a thorough comprehension of what happens 

 in the soil will teach us how to maintain the fertility of the soil more 

 surely than blind and rather purposeless experimentation. The great 

 majority of plat tests of fertilizers illustrate the impossibility of satis- 

 factory deductions from experiments entirely upon an empirical 

 basis. We must deal in irons and not in generations if agricultural 

 science is to be advanced by the cut-and-try method. 



[Cir. 113] 



