40 BULLETIN 1180, U. S. DEPARTMENT OF AGRICULTURE. 
experiments with soils from fields 1, 2, 3, and 4. In every case the 
soils nitrified ammonium sulphate satisfactorily, but the nitrates 
present in the soils two months after receiving cyanamid were fre- 
quently less than in untreated portions. A general average of the 
numerous determinations made showed that the soil of field 1 nitri- 
fied best, that from field 4 came second, while fields 2 and 3 were the 
poorest. This agrees almost exactly with the relative increases in 
cotton yields obtained from these various fields. The fact that all 
soils readily nitrified ammonium sulphate but not cyanamid indicates 
rather definitely that the dicyanodiamid formation in the poorly 
aerated and sometimes poorly drained soils of fields 2 and 3 was 
primarily responsible for the lack of nitrification and poor cotton 
yields with cyanamid. Very small amounts of this material are 
sufficient to prevent nitrification entirely. 
The crops which usually give the best results with cyanamid, 
judging from results reported in the literature and those here obtained, 
are the ones that have a long growing period and can utilize ammonia 
nitrogen. Crops that require nitrate nitrogen frequently make very 
poor growth, because cyanamid nitrifies so slowly. This fact is 
thought to explain the results here reported, where cotton frequently 
gave poor responses to cyanamid nitrogen, while corn always grew 
rapidly and produced as good yields as with standard fertilizers. 
Since the transformation of cyanamid nitrogen to nitrate nitrogen 
is usually a slow process, cyanamid should never be used as a fertilizer 
for quick-growing crops, such as vegetables, unless the material is 
applied several da}^s or weeks before seeding. Even then a nitrate 
fertilizer would probably prove more profitable. The use of nitrate 
nitrogen in combination with cyanamid is advisable provided such a 
mixture is a compatible one, as was not the case in the tests reported 
in this bulletin. 
The time and method of application are of very great importance in 
cyanamid fertilization. In order tliat sufficient time will be avail- 
able for nitrification, the material should be applied at least 10 days 
before seeding, or in the case of most perennial crops an early spring 
application before growth begins is best. In these experiments the 
cyanamid was usually applied at the time of seeding in order to 
conform to the prevailing American practice. A retarded early 
growth and a delayed maturity were the natural results. Applica- 
tions to growing crops usually depress growth for a month following. 
This occurred in the time-of-application studies reported on previous 
pages, particularly with cotton. Since corn can utilize ammonia 
it is less susceptible to what is ordinarily considered as bad practice 
in the use of cyanamid. With regard to the method of application, 
it seems that a more intimate mixing of the cyanamid with the soil 
than can be obtained by distribution in the row is desirable. 
The explanation for the peculiar behavior of cyanamid under 
some of the conditions outlined depends upon the chemical changes 
which take place. From the studies which have been reported on 
this subject and from those made in connection with the present 
investigation, it appears that almost immediately upon coming into 
contact with moist soil cyanamid changes into calcium-acid cyanamid, 
then free cyanamid (H 2 CN 2 ), urea, and eventually ammonia. A 
varying quantity of dicyanodiamid may be produced as a side reac- 
tion. The free cyanamid and dicyanodiamid are toxic to the nitrify- 
