48 
Journal of Agricultural Research voi. xxviii, no. i 
experiments were started. The better results obtained with the untreated as 
compared with the maximum hydrated and oiled material may be in part at¬ 
tributed to the presence of this dicyanodiamid in the latter. At no time could 
any dicyanodiamid be found in the original sample of untreated cyanamid. 
THE DECOMPOSITION OF UREA IN SOIL 
This experiment was conducted in order to obtain data in addition to that 
already given in Table III on the rate of ammonification and nitrification of 
urea. The procedure followed was the same as in the earlier experiment except 
that no calcium carbonate was used. Preliminary experiments on the recovery 
of known quantities of urea from soil immediately after the addition gave an 
average of 97.63 per cent. The failure to recover all of the added urea may have 
been due to the rapidity with which this compound is decomposed to ammonia. 
Fig. 3.—Diagram showing the rates of ammonification and nitrification of urea 
in the soil. Further experiments to determine if urea is broken up in the aeration 
method for ammonia gave negative results. 
The experimental results are given in Table V and figure 3. The results 
given for ammonia and nitrate nitrogen are the average of two determinations 
while those for urea are the average of three analyses, all made on the same 
sample of soil. 
The conversion of urea into ammonia took place very rapidly, 65 per cent of 
the urea having disappeared within 24 hours while at the end of 3 days no trace 
of undecomposed urea could be found. A comparison of the results given in 
Table V with those in Table III shows a maximum nitrification of 74.6 per cent 
after 57 days in the former case and 91.8 per cent in 28 days in the latter. This 
wide variation is due to the marked stimulation of nitrate formation by the 
presence of calcium carbonate. It will be remembered that exactly opposite, 
results were obtained in the case of cyanamid. 
