28 
COLORADO EXPERIMENT STATION 
Table No. 3. They indicate that this compound of ammonium is broken 
down with ease compared with the ammonium chlorid, but mot quite 
as readily as the sulphate. Eighteen of our soils gave positive 
gains in nitric nitrogen from the carbonate; one showed no increase and 
four produced less than the controls. We find the samples which failed 
to nitrify the carbonate the same four that fell below with the sulphate, 
and what has been said by way of an attempted explanation of this 
under the sulphate series should hold equally well here. With the 
exception of No. 78, all are high in chlorin. A few points of interest 
in connecting with these negatively reacting soils may be mention¬ 
ed here: No. 78, the raw adobe hill, failed by 8 p. p. m. to produce as 
much nitric nitrogen in the presence of the carbonate as of the sulphate; 
the vigorous denitrification appears to have carried the nitrates beyond 
the nitrite stage since the nitrous nitrogen is less than in the begin¬ 
ning. We have a rather striking coincidence in the exact agreement 
of soils 80, 81 and 86 with respect to the nitric nitrogen that they pro¬ 
duced in the presence of both ammonium carbonate and ammonium 
sulphate. No. 92, which failed to give a net gain in nitric nitrogen with 
(NH*) 2 SC>4 yielded an increase of 20 p. p. m. over the control with 
(NHOsCCh, and this with 7,800 p. p. m. of chlorin present. 
The average net gain in nitric nitrogen made by the positively 
reacting soils was 520.88 p. p. m., the maximum was 1148.0 p. p. m. by 
soil No. 97, and the minimum 20 p. p. m. by No. 92. 
The results of this study indicate that both our normal and in¬ 
cipient niter soils are equally efficient in nitrifying ammonium car¬ 
bonate. 
The presence of large quantities of initial nitrate in the soil 
without high chlorin such as we find in No. 95 with 600 p. p. m. of 
nitric nitrogen did not interfere seriously with the nitrificaton process. 
In this particular instance, a net gain of 680 p. p. m. of nitric nitrogen 
was secured, although the sample to begin with contained a large 
excess, it being the brown crust from a niter spot. 
Series IV. Dried Blood 
As stated elsewhere, we were curious to learn whether the am¬ 
monium compounds that are formed by the ammonification of pro- 
teid nitrogen, through the agency of ammonifying bacteria, would re¬ 
spond more or less readily to the nitrifying organisms than would the 
chemically pure salts. To this end, a fourth series of soils was pre¬ 
pared, to which dried blood was added to furnish the necessary organic 
nitrogen. 
The results of the experiment appear in Table No. 4. In the pre¬ 
vious investigation, we determined the ammonifying efficiency of soils 
from all of these localities except three and found them to be abundantly 
stocked with ammonifying organisms and capable of converting the 
nitrogen of the blood into ammonia nitrogen. Having ascertained this 
fact, we have proceeded on the assumption, in the present work, that 
ammonium compounds would be available for the nitrifying organisms, 
and that if there was no increase in nitrate at the end of the experi¬ 
mental neriod, it was chargeable to the nitrifying flora and not to the 
ammonifiers. 
