1164 
Journal of Agricultural Research 
Vol. XXVIII, No. 11 
not reported here, the soil is practically sterilized exactly as is the case with heavy 
applications of cyanamid. 
This experiment was planned to determine whether the marked stimulation to 
bacterial numbers following applications of cyanamid can be largely explained 
on the basis of its lime content. The results indicate that this is the explanation 
for a large part of the increase, but evidently the cyanamide and its transforma¬ 
tion products as well as the impurities in commercial cyanamid also enter into 
the results in a very marked manner. 
THE RELATIVE IMPORTANCE OF THE CYANAMIDE AND CALCIUM OXID 
IN CYANAMID IN INCREASING BACTERIAL NUMBERS 
In continuation of the work reported in Table III using the same methods 
and soil, an additional series of experiments was started on June 23, 1922, using 
pure cyanamide (H 2 CN 2 ) and calcium oxid singly and together in comparison 
with like applications of cyanamid basing the rates on the nitrogen and calcium 
contents of the cyanamid. These results are given in Table IV. 
Again it will be observed that cyanamid produced a big increase in bacterial 
numbers. With the three lowest applications, the larger the application the 
greater the stimulation, but with the heaviest application the numbers were 
less than with the medium rates, but still far above the control. Using calcium 
oxid in amounts comparable to that in the cyanamid, large increases in bacterial 
numbers were also noted and in every case the larger the application the higher 
the figures. In many respects, the data corresponds to that noted for cyanamid 
except that the largest application of calcium oxid did not produce a falling 
off as was observed with cyanamid. 
The effect of pure cyanamide was very peculiar. At the two smaller rates, it 
produced only moderate increases as compared with either cyanamid or calcium 
oxid, but with 50 mgm. N per 50 gm. soil, 36 times as many bacteria were 
present at the end of 13 days’ incubation as in the control. With double this 
application, the soil was partially sterilized. It is quite remarkable that cyan¬ 
amide, at one application produced such a marked effect, while at either slightly 
higher or lower rates showed only moderate effects. 
Table IV .—Numbers of microorganisms in soil receiving cyanamid , pure cyan- 
amide , and calcium oxid 
Treatment (per 50 gm. of soil) 
Millions per gram 
5 days 
13 days 
21 days 
Control.. _____ 
6.26 
2.85 
1.98 
Cyanamid 5 mgm. N _ . _ 
8.03 
4.13 
2.64 
Cyanamid 20 mgm. N_____-...-_ 
43.96 
23.39 
9.97 
Cyanamid 50 mgm. N_______-.. 
50.80 
54.16 
5.46 
Cyanamid 100 mgm. N........ 
17.20 
46.30 
14.66 
Calcium oxid 16 mgm ____ 
11.06 
5.30 
2.67 
Calcium oxid 64 mgm__ _ 
16.88 
8.11 
3.50 
Calcium oxid 160 mgm_____ 
25.90 
11.07 
7.03 
Calcium oxid 319 mgm___ 
71.05 
69.26 
8.24 
Pure cyanamide 5 mgm. N___ 
6.86 
3.75 
2.16 
Pure cyanamide 20 mgm. N....... 
9.81 
12.49 
6.46 
Pure cyanamide 50 mgm. N_• _. 
9.21 
102.84 
33.10 
Pure cyanamide 100 mgm. N _ _ _ _ 
.71 
.24 
.46 
Pure cyanamide 5 mgm. N+calcium oxid 16 mgm_ 
8.43 
6.93 
2.87 
Pure cyanamide 20 mgm. N+calcium oxid 64 mgm_____ 
19.87 
25.43 
16.16 
Pure cyanamide 50 mgm. N+calcium oxid 160 mgm___ 
107.08 
52.66 
6.76 
Pure cyanamide 100 mgm. N+calcium oxi£ 319 mgm__ _ 
1.47 
5.70 
6.14 
