30 
COLORADO EXPERIMENT STATION 
maintained them constant to the end, and while it can show no net gain 
in nitric nitrogen, it has not lost what it already had, as before. 
In soil No. 80, Series I and III, nitrification seems to have been 
retarded by the presence of the ammonium salts, due probably to 
combinations of chlorids with the sulphates or carbonates or perhaps to 
mere concentration of the saline solution. The dried blood in the pres¬ 
ent series has evidently changed the soil conditions quite materially, for 
here No. 80 gave a net gain of 50 p. p. m. nitric nitrogen and 88. p. p. m. 
of nitrons nitrogen over the control, whereas in both preceding studies 
it had shown a loss in the former but a gain in the latter due presumably 
to denitrification. 
Soil No. 88, which gave no gains in any of the preceding experi¬ 
ments, responded to the dried blood with a net increase of 140 p. p. m. 
of nitric nitrogen. 
Samples Nos. 81 and 86 were unable to utilize the dried blood in 
the manufacture of nitrates. These same soils, it will be remembered, 
were deficient in nitrifying efficiency when tested out with the ammon¬ 
ium salts. 
No. 81 showed the largest loss in nitric nitrogen, 620 p. p. m., of 
any soil in any series. 
No. 92, which gave no increase with the sulphate and chlorid, 
showed a gain of 20 p. p. m. here as with the carbonate. 
The maximum net gain in nitrogen was made by No. 96 with 820 
p. p. m. This figure is rather interesting in view of the fact that the 
yields of this soil from both ammonium carbonate and ammonium chlo¬ 
rid were among the lowest. The average gain for the positively reacting 
soils of this series was 431.50 p. p. m., and the minimum 20 p. p. m. by 
No. 92. 
The presence of large quantities of nitrate in the soil to begin with 
does not appear to interfere seriously with the nitrification of dried 
blood provided the chlorin is not also high; this is apparent from the re¬ 
sults of samples Nos. 81 and 95. Comparing the nitrifying efficiency of 
our positively reacting normal soils with that of our incipient niter 
soils, we find that in this series the normal samples have considerably 
the advantage; the normal gave an average gain of 519.60 p. p. m. of 
nitric nitrogen against 405.14 p. p. m. for the niter. 
SUM MM ARY OF COLORADO SOILS 
Seventeen or 73,91 per cent, of the soils under examination were 
able to convert the nitrogen of ammonium sulphates into nitrate nitro¬ 
gen ; eighteen or 78.26 per cent, accomplished the same with ammoni¬ 
um carbonate and twenty or 86.95 P er cent, with dried blood. Of the 
fifteen that received ammonium chlorid, nine or 60 per cent, gave 
positive results. 
The largest total amount of nitric nitrogen was produced from 
ammonium sulphate; the next largest from the ammonium corbonate, 
then the dried blood and least from the ammonium chlorid.. 
The largest amount of nitric nitrogen produced by any one soil 
