ATMOSPHERIC-XITROGEjtf FERTILIZERS. 41 
ing bacteria, and the ammonia can not be oxidized to nitrates until 
the injurious compounds are so dispersed, changed, or absorbed as to 
be no longer present in sufficient concentration to be injurious. 
Until this does occur the plants are forced to take up ammonia or 
undergo nitrogen starvation. The unusually green color of many 
plants fertilized with cyanamid is probably in some way connected 
with ammonia absorption. 
The explanation of why the retardation period following the use 
of cyanamid lasts for only a few days in one case and throughout 
the summer in another probably depends upon the particular com- 
pound primarily responsible for the effect. If it is merely ammonia 
or free cyanamid, these materials will be quickly changed or dis- 
persed and nitrate production may proceed normally. If dicyanodi- 
amid, the effect may be expected to continue for a considerable 
period, since the compound is not only relatively insoluble but not 
readily attacked by chemical or biological agents. 
SUMMARY. 
This bulletin presents the results of field tests with 10 atmospheric- 
nitrogen products conducted during a period of three years on an 
area of about 10 acres the first year and 20 acres the last two years. 
Cyanamid usually was not as satisfactory as the other sources of 
nitrogen, chiefly because so many factors influence the rate and 
manner in which the material is decomposed either in fertilizer 
mixtures or in the soil. When mixed with acid phosphate in large 
proportions the results were poor, probably owing to the transfor- 
mation of a portion of the cyanamid nitrogen to dicyanodiamid, 
a compound which is not only unavailable but toxic for some crops 
and for the nitrifying bacteria. Where applied separately with 
acid phosphate the results were good even with 1,000 pounds of 
an 8-8-4 fertilizer. Calcined phosphate and basic slag appear to 
be entirely satisfactory as to compatibility as sources of phosphorus 
for use with cyanamid. 
The behavior of cyanamid in the soil depends upon a number of 
factors, such as time and method of application and the type, com- 
position, temperature, and moisture content of the soil. Applica- 
tions should be made at the time of seeding, or preferably earlier. 
It is, furthermore, believed that thorough mixing of the cyanamid 
with the soil is preferable to drilling in the row. Even under the 
best conditions cyanamid nitrogen is converted to nitrates rather 
slowly and for this reason is usually slow to act. The soil condi- 
tions which are known to hasten nitrification are, in general, the 
ones which favor an efficient utilization of cyanamid. 
The marked differences in the response of different crops to cyana- 
mid under the same conditions has been very clearly brought out 
by the experiments with corn and cotton. Corn gave as good 
yields in most instances with cyanamid as with any other fertilizer 
used. Only a very temporary period of retardation was in evidence 
during early growth. Cotton was usually retarded for a consider- 
able period subsequent to germination and in most cases never 
produced as good growth or as large yields with cyanamid as with 
ammonium sulphate or sodium nitrate. This is believed to have been 
due to the fact that cotton requires nitrate nitrogen for its best 
