33 
equal facility. From the large number of cultures that have been 
reported and the many observations made it is safe to assume that the 
ammonia of natural soils is absorbed and assimilated to a greater or 
less extent by nearly all plants. We may conclude, therefore, that 
an important part of the action of heat on soils has to do with the pro- 
duction of ammonia. 
As previously stated, Schreiner and Lathrop (page 29) have shown 
that the major portion of the organic nitrogen compounds, split off 
from more complex bodies in soils under the action of heat, is also 
beneficial to plant growth. With the additional production of rela- 
tively large amounts of ammonia it is probable that marked stimu- 
lation would result. 
The effect of heat viewed from this standpoint is also of interest in 
its relation to the effects of partial sterilization. As already stated, 
one of the pronounced effects of partial sterilization, either with heat 
or volatile antiseptics, is the abnormal ammonification thus induced 
and which seems to be correlated with marked plant stimulation. 
In some Hawaiian soils the effect of partial sterilization on subse- 
quent ammonification has recently been found to be exceptionally 
great. If the accumulation of ammonia as a result of partial sterili- 
zation reacts beneficially on plants, we certainly have a right to con- 
clude that its direct production by means of heat would also prove 
stimulative to crops. 
EFFECTS OF BRUSH BURNING IN THE FIELD. 
With the view to determining the effects produced by burning 
refuse, brush, etc., in the field, a few samples of soil from spots where 
brush had been burned were examined at two different times. The 
brush was burned about September 1 and the samples were taken 
September 10 and November 7, respectively. Care was taken to 
remove the ashes so as to secure portions of the uncontaminated 
soil. Samples of unburned soil near by were taken at the same 
time. Ammonia and nitrates were determined in the samples as 
follows : 
Effects of burning brush on soil nitrogen. 
[Parts per million of nitrogen in air-dried soil.] 
As nitratos. 
As ammonia. 
Laboratory No. 
After 10 
days. 
Two 
months 
later. 
After 10 
days. 
Two 
months 
later. 
402 (burned ) 
6.5 
20.0 
• 6.0 
6.0 
16.0 
£2.0 
5.5 
18.0 
8.0 
8.0 
22.0 
52.0 
50.4 
39.2 
161.0 
21.0 
77.0 
8.4 
100.8 
402a (not burned; 
70.0 
403 (burned) 
10H. 4 
403a (not burned) 
32. 2 
404 (burned ) 
114 S 
30.8 
