Apr. 5, 1924 
Studies with Cyanamid 
67 
SUMMARY 
The study of the changes which cyanamid nitrogen and its transformation 
products undergo in the soil emphasized the following points: 
1. Cyanamid was rapidly converted into its various decomposition products, 
chiefly urea and ammonia. Tests for cyanamid showed none present after 5 to 
10 days depending upon the rate of application. Urea was likewise present for 
only very short periods, being broken up into ammonia so rapidly that no accu¬ 
mulation occurred. Other decomposition products of cyanamid which were 
precipitated by silver nitrate were present in soils receiving cyanamid for a con¬ 
siderable period after applying. No attempt was made to isolate these com¬ 
pounds but they probably consisted largely of dicyanodiamid and possibly 
guanylurea. 
2. The nitrification of cyanamid usually took place more slowly than tha4> of 
urea or ammonium sulphate and the larger the application the slower the process. 
After the initial retarding period of two to four weeks nitrification proceeded at a 
more nearly normal rate. Some of the transformation products of cyanamid are 
toxic to the nitrifying bacteria and where present in appreciable amounts in¬ 
directly cause an ammonia accumulation. 
3. Cyanamid which had been hydrated and oiled nitrified at practically the 
same rate as did the untreated material. The slight difference in favor of the 
latter is thought to have been due to the presence of a trace of dicyanodiamid in 
the hyrdated material and not to the presence of the oil. 
4. The addition of calcium carbonate to soil receiving cyanamid retarded 
nitrification, contrary to results obtained with urea and ammonium sulphate. 
This peculiar behavior was probably due to an increase in dicyanodiamid forma¬ 
tion in the presence of the calcium carbonate. 
5. The rate of nitrification of cyanamid at different moisture contents was the 
highest at one-fourth of saturation (10 per cent) while for urea the rate was 
higher with both one-half and three-fourths than with one-fourth. The maximum 
nitrate accumulation for both fertilizers was with 30 per cent moisture but in the 
case of cyanamid the nitrates present after two months was very nearly the same 
with either 10, 21 or 30 per cent. With 40 per cent moisture there was little if 
any nitrate formation. 
6. Nitrate formation from cyanamid was more rapid and complete at 38.5° C. 
than at lower temperatures. At room temperature no nitrification had taken 
place in one experiment after 42 days. At 30° C. the results were intermediate. 
Under similar conditions urea nitrified at all temperatures, the rate rapidly 
increasing up to 30° C. but decreasing at 38.5° C. 
7. The partial sterilization of soil with phenol practically stopped all nitrifica¬ 
tion of cyanamid. 
8. Dicyanodiamid when added to soil slowly disappeared, more than one-half 
being decomposed during a period of two months. The nitrogen accumulated 
in the soil as ammonia which was not readily nitrified. With 12.72 mgm. of 
nitrogen as dicyanodiamid per 250 gm. of soil 36 weeks were required for any of 
the added nitrogen to nitrify while with larger applications no nitrification took 
place in 40 weeks. In all cases where dicyanodiamid was applied the nitrate 
formation from the soil organic matter was markedly retarded. 
9. The nitrification of ammonium sulphate in the presence of dicyanodiamid 
was prevented for a period of 210 days where the dicyanodiamid was used at 
the rate of 10.5 mgm. per 100 gm. soil. Even as little as 0.1 mgm. per 100 gm. 
of soil greatly delayed nitrification. 
10. The rate of ammonification of urea was not appreciably affected by con¬ 
centrations of dicyanodiamid as high as 315.2 mgm. per 250 gm. soil. 
