B. P. I.— 233. 



VIll-CONDITIOXS AFFFXTIXG LEGUME IXOCULA- 



TIOX." 



By Karl F. Kellerman, PhyshlogiM in Charge of Soil Bac(enolo(jy ami Wnter 

 I\inficatio7i Inrestigatiow, and T. K. RoiuxsoN, Assiskml Phyifioloyist. 



INTRODUCTION. 



The widespread use of bacteria for inoculating leguminous crops 

 has made possible more accurate study of the conditions under which 

 a particular species of legume might be successfuU}' inoculated and 

 the conditions under which failure to obtain inoculation might be 

 expected. Inoculation tests carried on in different soils and under 

 different cultural and climatic conditions but using the same stock 

 culture have shown results so contiicting in certain cases that one is 

 bound to be misled by an}' general statement based on one factor 

 alone, such, for instance, as the condition of the bacteria used. 



To accept as indicative of the general usefulness of pure cultures 

 results obtained on a single type of soil is clearly opposed to progress 

 along a line of investigation now recognized as closely connected with 

 soil fertility problems. The advantage of numerous tests covering 

 many types of soil becomes increasingly apparent. The effect of pre- 

 vailing cultural practices is no less to l)e considered; aeration b}^ cul- 

 tivation, the use of lime, and the effect of such factors on the bacterial 

 flora, the bacteriological testing of the soil itself — all these problems 

 call for extensive field experiments to determine how far they may 

 become part of practical routine for successful farming. 



The work here recorded emphasizes the intimate connection of soil 

 bacteriology with certain phases of soil fertilit3\ Soil fertility is a 

 strictly relative term; it is possible for a soil to be fertile in regard to 

 one crop and unfertile in regard to another, the conditions of tem- 

 perature and moisture being optimum in each case. The interaction 



ffThe identification of soil bacteria and their distribution in and correlation with 

 different types of soil, the changes in the bacterial flora with different modes of 

 treatment and different systems of rotation, the individual and combined action of 

 the species in producing changes in the soil favorable or unfavorable to plant growth, 

 the introduction of favorable species and groups of species and their improvement 

 by selection or special cultivation, and the elimination of unfavorable forms are 

 problems calling for extended investigation; liut with the information already at 

 hand and work under way both in this country and in Europe it is not too much to 

 expect large increases in our present knowledge along these lines. —B. T. Galloway, 

 Pathologist and Physiologist, and Chief of Bureau. 



100— VIII ^^ 



