June 14,1924 
Effect of Cyanamid on Microorganisms in Soil 
1165 
Where cyanamide and calcium oxid were used together in the approximate 
proportions found in cyanamid, the figures show clearly the importance of cyan- 
amide in determining the results. At the two smaller rates, there was a fairly 
marked increase in numbers, probably due more to the calcium oxid than to the 
cyanamide. With the third highest rate, there was the usual marked stimulation 
observed with both the lime and cyanamide, used singly, as well as with cyanamid. 
However, the maximum effects were observed at the 5-day incubation period 
instead of 13 days as with cyanamide. Evidently, the lime was largely responsible 
for hastening the bacterial multiplication. With the highest application of the 
combination of cyanamide and calcium oxide, there was marked retardation at 
first followed by a small increase over the control later. In this case, the cyan¬ 
amide was the important factor and neutralized the good effect that the same 
application of lime produced in the absence of the cyanamide. 
EFFECT OF UREA, GUANYLUREA SULPHATE, GUANIDIN NITRATE, AND 
BIGUANID NITRATE UPON THE NUMBERS OF BACTERIA IN SOIL 
After observing the very marked effects of cyanamid on bacterial numbers, it 
was of interest to extend the previous studies to include some additional trans¬ 
formation products of cyanamide. In this connection, guanidin nitrate and 
biguanid nitrate were used, as well as guanylurea sulphate and urea, previously 
studied. All applications were based upon the nitrogen content, the rates being 
25-50, and 100 mgm. N per 50 gm. soil. In addition, sodium nitrate was used 
singly in amounts equivalent to the nitrate contents of guanidin and biguanid 
nitrates at the highest rates of application. In like manner, a test was included 
using magnesium sulphate equivalent to the sulphate content of the largest 
application of guanylurea sulphate. The data secured in this experiment, started 
on April 20, 1922, using the Susquehanna loam soil, are given in Table V. 
In marked contrast to the effect produced by cyanamide, all of the materials 
used in this experiment produced only slight effects. The increases and decreases 
noted were usually only comparatively slight and almost within the experimental 
error. In this particular experiment, a large proportion of these variations may be 
attributed to the fact that the dilution used in plating was much too small, and 
consequently a variation of three or four colonies on a plate made a very 
great difference in the final figures. 
Table V. —Numbers of microorganisms in soils receiving nitrogen in the forms 
of urea , guanylurea , guanidin , and biguanid 
« 
Treatment (per 60 gm. of soil) 
Mgm. 
Millions per gram 
N 
8 days 
18 days 
Control . _ 
1.70 
1.20 
25 
1.80 
1.05 
60 
1.77 
1.98 
100 
2.03 
1.15 
Guanylurea sulphate_ _ 
25 
1.50 
1.98 
Guanylurea sulphate . .-__ 
50 
1.33 
.65 
Guanylurea sulphate _ 
100 
1.23 
.67 
Guanidin nitrate....... 
25 
1.93 
1.15 
Guanidin nitrate__________- 
50 
3.67 
.43 
Guanidin nitrate.....-. 
100 
1.06 
1.67 
Biguanid nitrate_____ 
25 
2.20 
1.32 
Biguanid nitrate_______ 
50 
1.23 
1.20 
Biguanid nitrate - -- _ ___ 
100 
3.27 
1.25 
Sodium nitrate O 1 NO* in biguanid nitrate.. 
2.70 
1.20 
Sodium nitrate NOj in guanidin nitrate _ -_ 
2.23 
.83 
Magnesium sulphate SO 4 in guanylurea sulphate. _ 
2.30 
1.23 
96162—24f-9 
