SOME FACTORS AFFECTING NITRATE-NITROGEN ACCU¬ 
MULATION IN SOIL 
By P. L. Gainey, Soil Bacteriologist , and L. F. METZGER, Research Student , Research 
Laboratory in Soil Biology , Kansas Agricultural Experiment Station 
INTRODUCTION 
The literature of nitrification in soils impresses one with the varied 
technic employed in such studies. It is an exception to find identical 
methods in use in any two laboratories. In many instances the differ¬ 
ences are so slight that they would seem to have little effect upon nitrifi¬ 
cation, but in other instances the differences are too great, it would seem, 
not to influence bacterial activity. The variations in volume of soil, 
depth of column, ratio of volume to surface exposed, shape, size, and 
type of container, degree of compactness, and methods of preventing 
contamination and evaporation suggest that the variations which might 
be produced in bacterial activity could in part explain the wide variations 
in results often reported from different laboratories. 
PRELIMINARY EXPERIMENT 
Some preliminary experiments designed to test the validity of such a 
conception were conducted. No attempt was made to duplicate iden¬ 
tically the various methods that have been used or suggested, but the 
principal variable factors were varied sufficiently to produce different 
results, provided differences actually arose from such variations. In 
Table I are reported the variations to which a soil was submitted, to¬ 
gether with the results such variations produced upon nitrate accumu¬ 
lation. 
In these and most of the succeeding experiments an Oswego silt loam 
of the following mechanical analysis was used: Fine gravel, none; coarse 
sand, 0.6 per cent; medium sand, 0.3 per cent; fine sand, 1.5 per cent; 
very fine sand, 6.9 per cent; silt, 71.8 per cent; clay, 17.8 per cent. 
Ammonium sulphate was added at the rate of 60 mgm. of nitrogen per 
100 gm. of soil; calcium carbonate, 1 gm. per 100 gm. of soil; water, 27 
gm. per 100 gm. of soil. Incubation was for four weeks at room tem¬ 
perature. Nitrate nitrogen, as in all succeeding experiments, was de¬ 
termined by the phenoldisulphonic-acid method as modified by Lipman 
and Sharp (9). The results in this experiment are reported in milligrams 
of nitrogen recovered as nitrates per 100 gm. of soil. Ammonia was 
tested qualitatively by Nessler’s reagent. Where reported as “abund¬ 
ant," a heavy red precipitate was formed. Where reported as “some," 
Journal of Agricultural Research, 
Washington, D. C. 
kb 
(43) 
Vol. XI, No. 2 
Oct. 8, 19x7 
Key No. Kans.—10 
