42 
COLORADO EXPERIMENT STATION 
yield was 526 p. p. m.; from ammonium carbonate, the largest net gain 
by a Colorado sample was 1148 p. p. m., by a foreign soil, 606 p. p. m.; 
from dried blood the former gave 820 p. p. m., the latter 650 p. p. m. 
(See Plate I.) 
In looking over the net gain columns of the Colorado tables one 
sees but few positive results under 300 p. p. m. and many above 500 
p. p. m. with the exception of the ammonium chlorid series. On the 
other hand, an inspection, of the corresponding columns of the foreign 
group shows many figures between 20 and 90 p. p. m. and only a few 
above 250 p. p. m. 
A comparison of the average gains in the two sets is given in 
Tables 9 and 10. 
The second conspicuous difference between the two series we find 
in their inverse ability to nitrify the different materials placed at their 
disposal. To illustrate—52.94 per cent, of the Colorado samples made 
their largest net gains in nitric nitrogen from ammonium sulphate as 
compared with 29.41 per cent, of the others; 33.33 per cent of the soils 
TABLE NO. 9. —Average Net Gain in Nitric Nitrogen by Positively Reacting Colorado 
and Foreign Soils in Parts Per Million of Air-dried Soil. 
Nitrifiable substance added: 
Nothing 
(nh> 2 so 4 
(NH 4 ) 2 C0 3 
Dried Blood 
Colorado Soils. 
59.30 
672.00 
520.88 
431.50 
Foreign Soils. 
47.08 
150.82 
214.76 
267.39 
Excess of Colorado Soils over 
Foreign Soils . 
12.22 
521.18 
306.12 
164.11 
Gain per cent, by Colorado 
Soils . 
25.95 
345.56 
142.54 
61.37 
TABLE NO. 10.—Average 
Net Gain in 
Nitric Nitrogen by Colorado 
and Foreign Soils 
in Parts Per ] 
Million of Air-dried Soil, all 
Samples Considered. 
Nitrifiable substance added: 
Nothing 
(NH 4 ) 2 S0 4 
(NH 4 ) 2 co 3 d 
ried blood NH Cl 
4 
Colorado Soils. 
51.30 
484.26 
398.34 
341.30 56.80 
Foreign Soils. 
44.93 
110.36 
161.63 
214.72 
Excess of Colorado Soils over 
Foreing Soils. 
6.37 
373.90 
236.71 
126.58 
Gain per cent, by Colorado 
Soils . 
14.17 
338.80 
146.4S 
58.95 
from Colorado produced their highest yields from ammonium carbon¬ 
ate as against 35.29 per cent of the others; 30 per cent, of those from 
Colorado made their maximum gains with dried blood as compared 
with 44 per cent, of those from outside of the state. From this, it is 
very clear that the majority of the Colorado soils nitrify ammonium sul¬ 
phate most readily and dried blood least easily, whereas exactly the 
opposite is true of the foreign samples—ammonium sulphate least easily 
and dried blood most readily. (See Plate III.) 
The superior nitrifying efficiency of the Colorado soils and the 
inverse relation of their nitrifying power to that of the foreign samples 
suggest the following: 
1. The conditions for nitrification in Colorado soils are superior 
to those found in the other soils. 
