Dec. 4, 1916 
Nitrification in Semiarid Soils 
423 
soil weighs 2,000,000 pounds per acre of 6 inches, the average concentra¬ 
tion of dried blood that obtains in the field would be 0.054 P er cent. On 
the other hand, a concentration of 1 per cent was employed in the pre¬ 
ceding laboratory experiments, which is 18.5 times that which obtains 
in the field. 
It was at once suggested that an excessive concentration had been used 
in the laboratory. Accordingly a preliminary set of experiments was 
made, in which widely different concentrations of dried blood were added. 
The result was that the soil from the plots which had previously failed to 
nitrify a 1 per cent concentration of dried blood was found to support 
active nitrification of this material when added in low concentrations. 
An extended study has been made on the rates of nitrification of differ¬ 
ent nitrogenous materials when used in varying concentrations. Fresh 
samples were drawn from the same plots as in the preceding series. The 
nitrogeneous materials used were dried blood, bone meal, and ammonium 
sulphate, representing a high-grade and a low-grade organic form and an 
inorganic compound, respectively. The dried blood (13.20 per cent of 
nitrogen) was added in quantities ranging from 1 to 0.0625 P er cent. The 
bone meal (4.25 per cent of nitrogen) was varied from 4 to 0.25 per cent. 
Ammonium sulphate (21 per cent of nitrogen) was varied from 0.6 to 
0.0375 per cent. The experiments were made in duplicate. Control por¬ 
tions of each soil without the addition of nitrogenous material were also 
incubated. The incubation period was four weeks. The results are 
given in Table II. 
Table; II. —Nitrification as affected by different concentrations of nitrogenous materials 
Virgin soil. 
Control plot. 
Manured plot. 
Nitrogen 
Materials added. 
added per 
100 gm. 
Nitric 
Percent¬ 
Nitric 
Percent¬ 
Nitric 
Percent¬ 
of soil. 
nitrogen 
age nitri¬ 
nitrogen 
age nitri¬ 
nitrogen 
age nitri¬ 
found. 
fied. 
found. 
fied. 
found. 
fied. 
Mgm. 
P. p. m. 
P. p. m. 
P. p. m. 
T'Jnne . 
O 
34.O 
19. 6 
38-7 
Dried blood: 
1.0 per cent. 
132. 0 
66.0 
22. O 
0 
3-8 
21. O 
0 
3 i6 -° 
248. O 
140. O 
21. 0 
0.5 per cent. 
42. O 
57*5 
I. 2 
0. 2 
3**7 
3 °* 7 
0.25 per cent. 
33 * 0 
7 * 1 
120. O 
30*4 
0.125 per cent. 
rf-5 
hi. 0 
46.6 
99-0 
48. I 
96. O 
34 - 8 
0.0625 per cent. .*. 
! 8.25 
73 *o 
47*3 
75 *o 
67. I 
82. O 
5 2 * 5 
Bone meal: 
4.0 per cent. 
! 170. 0 
24- 5 
0 
18. 9 
O 
l88. O 
8.8 
2.0 per cent. 
: 85.0 
2. 1 
27* 5 
0.9 
240. O 
23*7 
1.0 per cent. 
! 42. 5 
109. 0 
17.7 
96. 0 
17.9 
220. O 
42. 7 
0.5 per cent. 
21.25 
99 * 5 
30*9 
104. 0 
39*7 
150.0 
5 2 * 4 
0.25 per cent. 
10.62 
80. 0 
43*3 
69.0 
46. 5 
91. O 
49*3 
Ammonium sulphate: 
126. 0 
0.6 per cent.*. 
15*4 
0 
31.0 
0.9 
94.O 
4.4 
0.3 per cent. 
63.0 
53 *o 
3. 0 
63.0 
6.9 
176. O 
21. 8 
O 
9.8 
0.15 per cent. 
31-s 
65.0 
82. 0 
19. 8 
158.O 
37*9 
0.075 per cent.... 
I 5 - 7 
78. 0 
28. 0 
' 88.0 
43-6 
148.0 
69. 6 
0.0375 per cent... 
Original soil. 
7-85 
69. 0 
1. 8 
44. 6 
74.0 
4 .S 
69.3 
112. O 
I 3 * 6 
93*4 
. 
