Apr. 5, 1924 
Studies with Cyanamid 
51 
with the exception of the first incubation periods. This initial retardation is 
characteristic of cyanamid and occurs even under the most favorable conditions. 
In the presence of 21 and 30 per cent of water urea nitrified more rapidly in all 
cases than did cyanamid and even at the end of two months the nitrate accumula¬ 
tion was still higher in the case of urea. It should be noted that nitrification 
was the highest with both materials in the presence of 30 per cent of moisture 
which corresponds to nearly three-fourths of saturation. At half saturation (21 
per cent), which is usually considered the optimum, the nitrate accumulation 
was appreciably below the figures for 30 per cent moisture. At 40 per cent 
moisture, which is near the saturation point, nitrification was negligible. In 
fact, there was usually a decrease of nitrates with an increase in the length of the 
incubation period. This may have been either the result of denitrification or 
utilization of the nitrates by microorganisms. 
Table VI.— Nitrate formation from cyanamid and urea in soils containing different 
percentages of moisture 
10 PER CENT MOISTURE 
Soil 
Urea 10 mgm. N 
per 100 gm. soil— 
Cyanamid 10 mgm. 
N per 100 gm. soil— 
Incubation period 
alone 
nitrates 
mgm. N 
Nitrates 
mgm. N 
Recovery 
of N as 
nitrates 
mgm. N 
Nitrates 
mgm. N 
Recovery 
of N as 
nitrates 
mgm. N 
Days 
14..... 
3.57 
5.15 
1.58 
2.53 
-1.04 
30...—. 
4.00 
7.95 
3.95 
7.73 
3.73 
44.....— 
4.47 
10.17 
5.70 
10.63 
6.16 
61... 
4.38 
11.94 
7.56 
12.07 
7.69 
21 PER CENT MOISTURE 
14... 
4.65 
7.72 
3.07 
3.50 
-1.15 
30...... 
5.27 
11.94 
6.67 
6.87 
1.60 
6.21 
14.37 
8.16 
12.27 
6.06 
61..... 
7.37 
16.21 
8.84 
14.77 
7.40 
30 PER CENT MOISTURE 
14...... 
4.16 
9.54 
5.38 
2.23 
-1.93 
30.... 
5.25 
13.61 
8.36 
7.35 
2.10 
44.. 
6.00 
15.95 
9.95 
13. 61 
7.61 
61... 
7.73 
17.16 
9.43 
15.60 
7.87 
40 PER CENT MOISTURE 
14_ .... 
0.38 
3.81 
3.43 
(«) 
(a) 
30...... 
.27 
1. 21 
.94 
2.42 
2.15 
44..... 
.12 
1.29 
1.17 
.35 
.23 
61..... 
.00 
1.08 
1.08 
.68 
.68 
« Lost. 
EFFECT OF TEMPERATURE UPON THE NITRIFICATION OF CYANAMID AND UREA 
This study of the nitrification of cyanamid was made according to the usual 
methods, using four different temperatures. One set of samples was kept in the 
open at a temperature varying from —9 to 18° C. Another series was main¬ 
tained at a room temperature of 15 to 20° C. The remaining two sets of samples 
were kept at constant temperatures of 30° and 38.5° C. in incubators. The 
nitrate determinations, which were made by the colorimetric method, are given 
in Table VII. These data are plotted in figure 5. 
