SOME FACTORS INFLUENCING NITROGEN FIXATION 
AND NITRIFICATION: 
BRUCE WILLIAMS 
Progress in the knowledge of soil bacteriological investigations 
must necessarily depend upon an acquaintance with the individual . 
factors that determine the efficiency of a particular group of soil 
organisms. Once the relative importance of these factors is deter- 
mined, the unessential discriminated from those which are of para- 
mount importance, a constructive policy for the promotion of 
bacterial activity may be announced that will be reflected in an 
increased fertility of agricultural lands. Investigations on the two 
general processes, nitrogen fixation and nitrification, have been 
reported recently from these laboratories? These reports have 
announced the effects of various organic and inorganic fertilizers 
in developing certain bacterial floras; the stimulus exerted by cul- 
tivation on the two processes just mentioned has been noted; and 
the comparison of a number of soil types with reference to their 
bacterial activities was emphasized in the investigations. The 
results of this work were such as to suggest a number of interesting 
possibilities to account for unusual conditions that were here and 
there encountered. Accordingly, an effort has been made to detect 
some of the influences that are responsible for these conditions and 
to place certain factors in the relative positions of importance. The 
data in this paper, which are in every case somewhat preliminary 
are closely connected with those of the previous publication and 
are accumulative toward establishing certain contentions which 
have heretofore been suggested. 
The moisture content of a soil with relation to its free nitrogen 
fixing power is a matter which it would be well to investigate. The 
rather meager information on this subject has recently been aug- 
* Paper 44 from Lab. Plant. Path. and Bact. Va. Agric. Exp. Sta. 
?ReEp, H. S., and Witrrams, Bruce, Nitrogen fixation and nitrification in 
various soil types. Va. Agric. Exper. Sta. Tech, Bull. 3. rors. 
311] [Botanical Gazette, vol. 62 
