Apr. 5, 1924 
Studies with Cyanamid 
49 
The importance of the manner in which the percentage nitrification is deter¬ 
mined needs to be emphasized. There is no satisfactory method of measuring 
the actual per cent of the added nitrogen converted into nitrates in soil contain¬ 
ing a mixed biological flora. All that is done is to determine the nitrates which 
accumulate over any given period. While the agents of decomposition are 
converting the nitrogen to ammonia, which in turn is oxidized to nitrites and 
nitrates, there are also numerous other organisms which are using the nitrates 
for their own growth. In this case the nitrates are usually converted into organic 
forms but under certain conditions may be merely denitrified. The soil condi¬ 
tions are, therefore, extremely important in determining the maximum nitrate 
accumulation at any given time. The more favorable the conditions for nitrate 
formation the quicker the maximum nitrate accumlation and usually the higher 
the figures. This is due chiefly to tlie fact that less time is available for the organ¬ 
isms, other than nitrifiers, to utilize the nitrate nitrogen. Where conditions 
permit only a slow rate of nitrification the nitrates may be utilized almost as 
fast as formed. The nitrogen thus converted into the organic form is again 
nitrified when the organisms die. Finally, an equilibrium point is reached after 
a long period where nitrate formation and nitrate utilization practically balance 
under a constant set of conditions. The nitrate nitrogen present at such a point 
is considerably lower than the maximum nitrate accumulation. 
Table V .—Ammonification and nitrification of urea 
Soil alone 250 gm. 
Urea 52.25 mgm. N per 250 gm. soil 
Incubation period 
Recovery of N 
Ammonia 
mgm. N 
Nitrates 
mgm. N 
Urea 
mgm. N 
Ammonia 
mgm. N 
Nitrates 
mgm. N 
Ammonia 
mgm. N 
Nitrates 
mgm. N 
Total, 
including 
urea 
mgm. N 
Days * 
0.. 
1.88 
1.63 
52.25 
1.88 
1.63 
1... 
3.40 
2.40 
17.92 
37.73 
4.08 
34.33 
1.68 
53.93 
3.. 
3.81 
3.80 
.00 
61.81 
4. 73 
58.00 
.93 
58.93 
5.... 
3.26 
5.43 
.00 
58.70 
8.23 
55.44 
2.80 
58.24 
8... 
2.81 
7.85 
.00 
51.54 
13.82 
48.73 
5.97 
54.70 
12... 
1.88 
10.01 
.00 
40.02 
23.39 
38.14 
13.38 
51. 52 
16..... 
.11 
9.26 
.00 
29.61 
32.53 
29.50 
23.27 
52. 77 
22.. 
.47 
10.09 
.00 
22.31 
40.65 
21.84 
30.56 
52.40 
36__ 
1.12 
12.08 
.00 
17.37 
49.00 
16.25 
36.92 
53.17 
57.. 
1.30 
15. 57 
.00 
16. 53 
54. 55 
15.23 
38.98 
54.21 
The necessity for having a neutral or basic soil reaction in order to secure a rapid 
formation and accumulation of nitrates is very important in this connection. As 
nitric acid is formed, available basic elements must be present for the formation of 
neutral salts; otherwise further nitrification is practically prohibited. At the 
same time the growth of soil fungi, which prefer an acid medium, is favored and 
these organisms help further to decrease the nitrate supply. The failure of cal¬ 
cium carbonate to favor the nitrification of cyanamid, as previously mentioned, is 
an exception, but this is thought to be due to the increase in dicyanodiamid under 
such conditions. 
EFFECT OF MOISTURE UPON THE NITRIFICATION OF CYANAMID AND UREA 
The use of cyanamid as a fertilizer under field conditions has shown quite variable 
results apparently due largely to seasonal conditions in many instances. For 
instance, it has been stated that a wet period in the early summer retards the 
nitrification of cyanamid and hence poor responses from the use of the material 
are secured. Again, it has been claimed that cyanamid should be applied only 
