J 
80 SOILS OF THE TRUCKEE-CARSON IRRIGATION PROJECT. 
The fact that nitrification was feeble in the good soil and also in 
one of the poor soils should not be overemphasized, for soils that will 
nitrify under normal conditions frequently fail to do so in solutions. | 
On the other hand, the rapidity with which the nitrate bacteria 
worked in solutions, even when they failed to do so in the soil, is 
interesting and almost without parallel. It is not surprising that a 
soil should fail to nitrify in solution, but it is remarkable that samples 
which failed to nitrify when kept warm and moist—ideal conditions 
for nitrification—should produce nitrates rapidly when inoculated 
into solutions. 
The production of ammonia from organic material by soil bacteria 
furnishes a means of measuring the power of the soil flora to break 
down nitrogenous organic substances. Thus it would seem that the 
soils of the plats in which organic matter remained indefinitely in a 
DEPTH AT WHICH SAMPLES WERE TAKEN. 
0706” 6012” 127018" 187024” 
3) 
on) 
=) 
1100 
x 
S8 
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SS 
aS 
xs 
Wy 
8 
Re 
AT: 
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Fig. 19.—Diagram showing the ammonification of peptone in 7 days in samples of soil from plat 350 (good 
soil) and from plats 330 and 340 (poor soil), Truckee-Carson: Experiment Farm. 
state of preservation must have a very low ammonifying power. 
The medium described previously, consisting of 1.5 per cent peptone 
and inorganic salts, was inoculated with samples from plats 330, 
340, and 350, and the ammonia produced determined at 10-day and 
20-day incubation periods by distillation with magnesia.! The 
results of this experiment are shown in figures 19 and 20. 
As the ammonification of the samples of poor soil, plats 330 and 
340, was very similar, the results are averaged and shown as a single 
curve. 
The fact that there is no increase between the 7-day and 15-day 
periods indicates that the maximum had been reached before any 
1 Dr. J. G. Lipman has recently suggested the use of dried blood as a source of 
nitrogen for work of this character. See Lipman, Jacob G., and Brown, Percy E., 
‘“‘Experiments on Ammonia and Nitrate Formation in Soils,’’ in Centralblatt fiir 
Bakteriologie, Parasitenkunde und Infektionskrankheiten, pt. 2, vol. 26, no. 20-24, 
April 9,1910, pp. 590-632. 
211 
