the: nitrifying efficiency of certain COLORADO SOILS 
39 
COMPARATIVE SUMMARY OF COLORADO AND FOREIGN 
SOILS. 
A comparison of the nitrifying efficiencies of these two groups of 
soils, taken as integrals, shows at a glance that the Colorado samples 
are superior to the others in their power of converting arnmoniacal 
and proteid nitrogen into nitric nitrogen. 
Considering only those soils that gave a positive reaction for nitri¬ 
fication, we find that the average net gain in nitric nitrogen made by a 
Colorado soil from ammonium sulphate was 672 p. p. m., while that of 
a foreign sample amounted to only 150.82 p. p. m.; again, the former 
TABLE NO. 8.—Increase in Nitric Nitrogen in Colorado Soils and Foreign Soils Without 
the Addition of Any Nitrifiable Substance. .Nitrogen in Parts Per Million of Air-dried Soil. 
Duration of Experiment: 6 Weeks at 28 Degrees C. 
Colorado 
A 
Soils 
Foreig: 
A 
n Soils 
r 
•\ r 
Sample 
Sample 
No. 
At beginning 
At end 
Net gain 
No. At 
beginning 
At end 
Net gain 
75 
7. 
64. 
57. 
52 
7. 
60. 
53. 
76 • 
54. 
110. 
56. 
53 
5. 
Trace 
—5. 
77 
26. 
76. 
50. 
54 
5. 
90. 
85. 
78 
140. 
140. 
0 . 
55 
9. 
70. 
61. 
79 
5. 
66. 
61. 
56 
11. 
50. 
39. 
80 
13. 
50. 
37. 
57 
7. 
46. 
39. 
81 
1360. 
1360. 
0 . 
58 
7. 
50. 
43. 
82 
46. 
120. 
74. 
59 
14. 
60. 
46. 
83 
6. 
100. 
94. 
60 
6. 
70. 
64. 
84. 
Trace 
68. 
68.— 
61 
3. 
20. 
17. 
85 
6. 
60. 
54. 
62 
4. 
24. 
20. 
86 
130. 
240. 
110. 
63 
4. 
46. 
42. 
87 
6. 
40. 
34. 
64 
6. 
70. 
64. 
88 
70. 
100. 
30. 
65 
4. 
24. 
20. 
89 
180. 
260. 
80. 
66 
40. 
126. 
86. 
90 
13. 
60. 
47. 
67 
120. 
140. 
20. 
91 
Trace 
40. 
40.— 
68 
7.4 
40. 
32.6 
92 
320. 
320. 
0 . 
69. 
2. 
30. 
28. 
93 
4. 
48. 
44. 
70 
5. 
34. 
29. 
94 
34. 
92. 
00 
71 
0 . 
12. 
12. 
95 
600. 
640. 
40. 
73 
7.4 
70. 
62.6 
96 
20. 
60. 
40. 
74 
26. 
160. 
134. 
97 
20. 
132. 
112. 
yielded 520.88 p. p. m. from ammonium carbonate and the latter but 
214.76 p. p. m.; from dried blood the Colorado soils averaged 431.50 p. 
p. m. as compared with 267.39 f° r the other series. This means that 
the Colorado samples produced an average of 521.18 p. p. m. or 345.56 
percent, more nitric nitrogen from ammonium sulphate than the other 
soils; that they yielded an average of 306.12 p. p. m. or 142.54 per cent, 
more from the ammonium carbonate, and 164.11 p. p. m. or 61.37 per 
cent, more from the dried blood. (See Plate II.) 
The maximum net gain produced by a Colorado soil from ammonium 
sulphate amounted to 972 p. p. m., while the highest foreign (1) 
(1) Inasmuch as the Kansas 6oil is in all essentials a Colorado soil, it has not been 
considered in this comparison. 
