The Relation of SilUur to Soil Fertility. 625
added to the Fayette County soil accounts for this but this is
hardly probable in view of the fact that adding calcium car-
} bonate to the Graves County soil did not promote the oxida-
tion of the sulfur as will be seen from a comparison of Nos.
2, 3, 6 and 7 on that soil. Furthermore, it h s just been
shown that the oxidation of the sulfur proceeds with about
the same rapidity regardless of the acidity of the soil.
Another possible explanation is that the Graves County
soil was previously heated for one hour between 95 degrees
and 100 degrees C. while the other was not, and this may
account for the above differences, but further experiments
are necessary in order to verify this/point.
. EXPERIMENT III.
The sand to which sulfur had been added in Series VIII
was used for the experiment below:
Table X[V—Oxidati0n of Sulfur to Sulfur Trioxide in Sand of Series VIII. -
Jar Per cent Sulfate Per cent
Sulfur. Sulfur
At the begin- After 205 Oxidized.
ning. days.
No. 18 50 lbs. sulfur per A. .003 .009 120
" 19 100 “ " “ '“ .003 .012 120
“ 20 500 " " " " .005 .014 32
“‘ 21 1000 “ “ “‘ " .005 .023 34
" 22 No sulfur added .002 .006
The above results are probably too high for the amount of
sulfur oxidation because of the presence of some pyrite
in the sand which was also partially oxidized. There is no
doubt however but that some of the sulfur was oxidized in
these experiments but not to the extent that it was in the
soils.
Oxidation of Organic Sulfur to Sulfur Trioxide in Manure and
Manure—Soil Mixtures.
The object of these experiments was to determine if the
‘ organic sulfur of manure is oxidized to sulfate both in the A
presence and absence of soil. The material used was fresh
air-dried horse dung which had been ground very fine.