54 
Journal of Agricultural Research 
Vol. XXVIII, No. 1 
are based upon the dry weight of the soil. The analyses, which were made by 
the colorimetric method, are given in Table VIII and figure 6. 
The presence of phenol even in the smallest amounts used decreased nitri¬ 
fication in practically every instance and at percentages above 0.1 per cent 
prevented nitrification altogether. There was a very slight stimulation of nitri¬ 
fication at 0.01 per cent at the end of two weeks but not-later. It is quite evident 
that phenol is very injurious to the nitrifying organisms, probably to an even 
greater extent than for other groups of bacteria. A partial sterilization of the 
soil could not, therefore, prove beneficial to nitrification if the nitrifiers were the 
first organisms to be killed. In Table VIII it will be observed that in most cases 
slightly more nitrates are present in the soils containing 1 and 2 per cent of 
phenol than with 0.2 to 0.4 per cent. This is probably because the larger per¬ 
centages of phenol completely sterilized the soil while with the smaller appli¬ 
cations some groups of organisms survived and used up the nitrates present. 
With the highest percentages of phenol the nitrate content of the soil remained 
at near that of the dry soil prior to incubation. With the lower percentages the 
phenol practically stopped all nitrification for the first two weeks but there was 
a partial recovery later. 
PART II. CHANGES WHICH DIC YANODI AMID, GUANYLUREA,* GUANIDIN, 
AND BIGUANID NITROGEN UNDERGO OR PRODUCE IN SOIL 
COMPARATIVE RATES OF NITRIFICATION OF DICYANODIAMID, GUANYLUREA SUL¬ 
PHATE, AND AMMONIUM SULPHATE 
This experiment was made for the purpose of determining if dicyanodiamid 
and guanylurea sulphate nitrify in the soil provided a considerable period of time 
is allowed for the process to take place. For comparison ammonium sulphate 
