40 
Journal of Agricultural Research 
Vol. XXVIII, No. 1 
Brioux, the previous investigations noted agree that dieyanodiamid does not 
nitrify. Using the ordinary applications of nitrogen and the short incubation 
period, the present work bears out this statement, but using 12.7 mgm. of nitrogen 
per 250 gm. of soil a nitrification of 38.6 per cent was obtained after 40 weeks. 
It is logical to suppose that nitrification should eventually take place since 
ammonia is formed fairly readily. The extreme toxicity of the dieyanodiamid 
for the nitrifying organisms prevents the normal oxidation process until most 
of the material has gone over to ammonia and the bacteria have recovered. 
It is this property of dieyanodiamid which is largely responsible for its injurious 
effect in fertilizers, but doubtless it is also directly toxic to many plants. 
GUANYLUREA 
The experimental work with guanylurea which has been reported is very 
limited and consists for the most part of plant culture studies. Since such studies 
are not directly related to the work here reported no references are given. It is 
sufficient to state that for the most part guanylurea has not served as a satis¬ 
factory plant food and in some cases has been reported as toxic. The behavior 
of the material in laboratory studies would lead us to expect just such a response. 
The material ammonified very slowly, and hence nitrate formation was limited. 
Where guanylurea sulphate was applied with ammonium sulphate the nitrifica¬ 
tion of the latter was inhibited for some time, but the toxic effect was decidedly 
less than with dieyanodiamid. However, such large quantities of gaunylurea 
sulphate were required to appreciably affect the oxidation of ammonium sulphate 
under laboratory conditions that it seems highly improbable that the material 
would ever be present in fertilizers in quantities sufficient to be injurious to 
field crops. Nitrogen present in the guanylurea form should be considered as 
inert material without fertilizer value. 
GUANIDIN 
Guanidin has given quite variable results when used as a fertilizer. In most 
cases the nitrate salt has been used and any increases in growth have been 
attributed to the nitrate rather than to the guanidin. Again, the nitrification 
experiments would lead us to expect the material to be an unsatisfactory source 
of nitrogen since it prevented nitrification for several weeks after application. 
Later it was quite rapidly converted into nitrates. If used on a soil containing 
sufficient nitrate nitrogen to supply the needs of the plants for the first four to 
eight weeks until the guanidin nitrogen had become available then the salts 
might act as good fertilizers. This also explains why in some cases guanidin 
salts gave better results on the second crop than on the first. 
BIGUANID 
Laboratory or field studies with biguanid nitrogen are very limited and its 
value still remains to be established. Reis {2Jf) found that in the laboratory 
the compound could be used by microorganisms if the concentration was suffi¬ 
ciently low. In the present nitrification studies a maximum conversion of 9.7 
per cent was obtained after 50 days. This figure is so low that the slight increase 
in nitrates may have come from the soil organic matter rather than from the 
biguanid nitrogen. Again, the increase may have represented merely the injury 
which the biguanid caused to the organisms which use nitrate nitrogen. 
PLAN OF THE WORK 
The experiments, which consisted chiefly of ammonification and nitrification 
studies, were conducted in the laboratory, using either 100 or 250 gm. of air-dried 
