Apr. 5,1924 
Studies with Cyanamid 
39 
and nitrification is inhibited. In further work {4) with cyanamid he concluded 
that urea formation is the result of a purely chemical process and not biological. 
The breaking down of the urea is the result of the work of microorganisms. 
Cyanamid decomposition was more rapid in clay than in sandy soils. 
The wide variations in the results reported by investigators who have studied 
cyanamid decomposition may be attributed largely to the differences in the 
methods of experimentation, including variations in the cyanamid and soils used. 
For instance, any experimentation with cyanamid containing appreciable quan¬ 
tities of dicyanodiamid or under conditions that favored its formation would 
undoubtedly greatly affect the conclusions reached by the investigator. This 
point will be considered more fully in the latter part of this report. However, 
the most recent investigations, as well as the observations of the writers, make 
it seem ^probable that under normal soil conditions cyanamid quickly changes 
into calcium acid cyanamid, then free cyanamid, urea, and ammonia. The 
ammonia is in turn oxidized to nitrites and nitrates. Dicyanodiamid is produced 
as a side reaction but only in small amounts, except under unfavorable soil con¬ 
ditions. This point has been considered in another publication {!) particularly 
in relation to the utilization of cyanaihid by plants. The exact nature of the 
changes taking place, whether the result of chemical or biological action, is still 
disputed. However, it seems that the changes which result in the production 
of urea from cyanamid are largely, if not wholly, chemical and physical. Colloids 
are especially important in hastening these processes. The formation of ammonia 
from urea and its oxidation to nitrates is the result of the work of microorganisms. 
DICYANODIAMID 
In a study of dicyanodiamid De Grazia (6) failed to obtain nitrification. 
Perotti {23) studied the growth of bacteria on culture media containing dicyano¬ 
diamid and concluded that it is a good nitrogen food for many microorganisms. 
Ulpiani {26) reported that dicyanodiamid is slowly converted into ammonia. 
Loew {17) found that dicyanodiamid is not a good source of nitrogen for many 
kinds of soil bacteria. Lohnis {16) failed to secure any evidence that bacteria 
attack dicyanodiamid in either dilute or concentrated solutions. Stutzer {25) 
reported that dicyanodiamid can not be used by microorganisms, but in the 
soil is converted into ammonia by the chemical action of certain soil constituents. 
Reis {24) stated that certain microorganisms can use dicyanodiamid and also 
guanylurea and biguanid nitrogen in concentrations of less than one part per 
thousand of water. Brioux {2) found that if thoroughly mixed with the soil 
dicyanodiamid is quickly converted into ammonia and nitrified. Cowie {3) 
failed to obtain any evidence of nitrification of dicyanodiamid in soils even after 
several months. Furthermore, it was toxic to the nitrifying organisms and 
stopped the oxidation of ammonia in soils containing ammonium sulphate. It 
did not prevent the formation of ammonia from cyanamid or other forms of 
nitrogen but it did prevent the oxidation to nitrates, resulting in an ammonia 
accumulation. This extreme toxicity was limited to the nitrifying bacteria, 
the other soil organisms apparently being practically unaffected. Lin ter {11) 
did not find that any decomposition of dicyanodiamid occurred in soils during 
a period of several days. 
The results of the investigations mentioned vary as to the readiness with 
which dicyanodiamid is attacked by bacteria. Where decomposition was 
obtained, some writers attribute it to purely chemical action, others to biological. 
No attempt was made in the work reported here to determine the agents respons¬ 
ible for the breaking down of the compound, but certainly there is no doubt but 
that the material does go over to ammonia. With the exception of the work of 
