34 
Here again it is shown that an increase in the ammonia and a de- 
crease in nitrates takes place in soil heating. The content of ammo- 
nia and nitrates at the end of two months is of special interest. The 
above data show that not only is ammonia formed by the action of 
heat but that subsequently ammonification took place at a greater 
rate in two cases out of three than in the unburned soils. Nitrifica- 
tion, however, was not restored under the existing field conditions. 
It is probable that reinoculation with both the ammonifying and 
nitrifying organisms gradually took place, but the lack of aeration 
prevented the development of the nitrifying bacteria. These soils 
had not been cultivated for two years previously and received no 
tillage during the time of observation. It is not possible to state the 
temperature to which the soil was heated in these instances. An ap- 
proximate test applied in another locality, however, indicates that 
the burning of small brush heaps similar to those burned on the soils 
above discussed created a temperature of about 200° C. 6 inches 
below the surface. The temperature would naturally vary greatly 
from place to place. 
EFFECTS OF HEAT ON THE ORGANIC NITROGEN. 
Having found that large amounts of ammonia are formed from the 
action of heat, a study of the organic nitrogen as affected by heat 
seemed of interest. It is well known that ammonia is one of the 
cleavage products of protein hydrolysis. It is also known that in 
the destructive distillation of organic nitrogenous substances ammo- 
nia is one of the decomposition products. It was observed that the 
amounts of ammonia recovered from heated soils by means of dis- 
tillation were not proportional to the total nitrogen present, but 
seemed to depend largely on the type of the soil. The amount of 
ammonia obtained, for example, from soil No. 335 was very much 
less than that from the other samples studied (page 32). Ammonia, 
therefore, was probably volatilized and driven out of the soil to a 
greater extent in some instances than in others. Soil 335 is a sandy 
soil composed very largely of coral sand (CaCO s ). In the foregoing 
work total nitrogen determinations were not made. Hence it is im- 
possible to correlate the rise and fall of ammonia with losses of 
nitrogen. 
In order to throw further light on these questions total nitrogen 
and the several groups of nitrogen compounds rendered soluble in 
boiling hydrochloric acid were studied. For this purpose the 
method of Hausmann 1 as modified by Osborne and Harris 2 was ap- 
plied. This method was devised for a study of protein chemistry, 
but has been previously used by Jodidi and others in studying the 
organic nitrogen of soils. 3 
Ztachr. Physiol. Chem., 27 (1899), p. 95. Jour. Amer. Chem. Soc, 25 (1903), p. 323. 
Michigan Sta. Tech. Bui., 4 (1909); Iowa Sta. Research Bui., 1 (1911). 
