428 
Journal of Agricultural Research 
Vol. VII, No. 10 
per cent dried blood and 0.15 per cent ammonium sulphate; but it pro¬ 
duced no effects on the nitrification of a concentration of 0.1 per cent of 
dried blood. 
With one exception it is noteworthy that the effects produced by either 
sodium carbonate or sodium sulphate were quite similar when equal 
amounts of nitrogen in the form of dried blood and ammonium sulphate 
were employed in low concentrations. 
The above results are in harmony with those of Lipman (18) in showing 
that sodium carbonate is extremely toxic to the nitrification of a high 
concentration of dried blood and far more toxic than sodium sulphate. 
NITRIFICATION DURING DIFFERENT LENGTHS OF TIME 
In the preceding studies the samples were incubated for four weeks, 
and, as already stated, conclusions on the relative rates of nitrification 
of different materials and in different soils have frequently been drawn 
from data obtained in this way. In the light of the preceding results it 
becomes a matter of interest to study nitrate formation at different 
intervals of time. In a preliminary study with the use of 1 per cent of 
dried blood in soil from the control plot it was found that no nitrifi¬ 
cation took place during a period of 68 days. In another series with the 
use of the same soil the incubation period was extended to 105 days, with 
the same result. With still other soils in which a concentration of 1 per 
cent of dried blood failed to be nitrified in four weeks, it has been found, 
however, that active nitrification may set in later, and in some cases 
eventually becomes quite as active as in soils which have the power of 
nitrifying 1 per cent vigorously within four weeks. 
For the purpose of studying nitrification progressively with low con¬ 
centrations of materials, 2,000 gm. of the fresh soil from the check and 
manured plots were kept in large jars. Dried blood and ammonium 
sulphate were added in quantities supplying 10 mgm. of actual nitrogen 
per 100 gm. of soil. The mositure content was brought up to 15 per cent 
and maintained near this point by the occasional addition of distilled 
water as evaporation took place. The soils were incubated as before. 
One-hundred-gm. portions were withdrawn at intervals and the nitrate 
determined, as shown in Table VI. 
Table VI .—Nitrification during different intervals of time 
Nitric nitrogen (parts per million). 
Soil. 
Nitrogenous materials 
added. 
Origi¬ 
nal 
soil. 
After 
4 • 
days. 
After 
days. 
After 
days. 
After 
days. 
After 
3 * 
days. 
After 
a 9A 
days. 
Control plot... 
Manured plot.. 
Control plot... 
None. 
I. 2 
4.0 
7.0 
7*4 
9. O 
7 * 5 
16. 5 
.do.. 
Dried blood. 
4.9 
I. 2 
9.8 
2. 2 
10. 0 
10. 4 
12. 0 
33 * 5 
13. 2 
66. 0 
14.0 
60. 0 
23.O 
72. 0 
Manured plot.. 
Control plot... 
.do. 
Ammonium sul¬ 
4*9 
1. 2 
10. 4 
4-4 
44 - 0 
16. 5 
58. 0 
37 * 0 
73 *o 
65. 0 
64. 0 
76. 0 
64. 0 
88.0 
Manured plot.. 
phate. 
4-9 
14.4 
60. 0 
72. 0 
96. 0 
96. 0 
96. O 
