NITRIFICATION OF SAMPLES IN SOLUTION. 19 
explained, however, by the original high nitrate content of the soil, 
as there is often a tendency for the nitrifying power of a soil to 
decrease as nitrates accumulate. 
NITRIFICATION OF SAMPLES IN SOLUTION. 
In order to further test for the presence of nitrifying bacteria and 
also to study some of their characteristics, inoculations were made 
DEPTH AT WHICH S4IIIPLES WERE TAKEN. 
67012” 1270187 187024” 247036” 
PARTS FER /4/LL/0N OF CHLOAIDS. 
R 
N 
IS 
S 
% 
x 
= 
: 
8 
S 
S 
= 
S 
N 
S 
& 
w 
S 
x 
Fic. 12.—Diagram showing the nitrification of ammonium sulphate in samples of soil from different depths 
from plats 260 and 270, Truckee-Carson Experiment Farm. Original nitrate present in samples from 
plat 260: Depth, 0 to 6 inches, 62 parts per million; 6 to 12 inches, 30; 12 to 18 inches, 18.75; 18 to 24 
inches, 35.7; 24 to 36 inches, 30. From plat 270: Depth, 0 to 6 inches, 100 parts per million; 6 to 12 
: inches, 27.7; 12 to 18 inches, 30; 18 to 24 inches, 40; 24 to 36 inches, 50. 
into media consisting entirely of inorganic material which is not suit- 
able for the growth of saprophytic bacteria.t Curves have not been 
plotted from the data thus obtained, as the conditions were too 
abnormal to warrant considering the differences from a quantitative 
1 Winogradsky and Omelianski’s Fluid Culture-Medium for Isolating the Nitrate 
Bacteria from Soils, and Winogradsky and Omelianski’s Fluid Culture-Medium for 
Isolating the Nitrite Bacteria from Soils. Centralblatt fiir Bakteriologie, Parasiten- 
kunde und Infektionskrankheiten, vol. 5, pt. 2, 1899, pp. 537-549. 
211 
