622 Bulletin N0. 188.
The above experiments show that alfalfa readily appro- _
priates sulfur for its own growth whether the source of sup-
ply be the element or certain of its compounds.
Oxidation of Sulfur to Sulfur T rioxide in the Soil.
Mention has been previously made that when sulfur is
added to the soil, it is rapidly oxidized to sulfate and in this
form is probably taken up by the plant. That this is true
with respect to soil and to a lesser extent with sand, can be
seen from the following experiments which have been made
along this line.
The procedure used was to determine the sulfates in the
soil or sand immediately after adding the sulfur and then
later after the plants were grown on it. The official
method"‘ for the strong hydrochloric acid digestion of the
soil was used for the sulfate determinations and all samples l
were air—dried and put through a 100 mesh sieve for
analysis. "
ICXPISRIMENT I.
The soil to which sulfur had been added in Series I was
used for these experiments and gave the following results:
Table Xl. Oxidation of Sulfur to Sulfur Trioxide in Soil of Series I.
Box   Per cent Sulfate Sulfur Per cent l
` lr -— » we Sulfur
At the After Oxidized
_ Beginning 123 Days
No.1 No sulfur added. .012 .011
" 2 100 lbs. sulfur per A. .012 :016 60
" fl 500 “‘ " U " ·. .013 .032 57
il After
`_ 110 Days
" 3 No sulfur added. .009 .010
" 0 100 lbs. sulfur added. ` .012 .015 45
" T soo ·‘ " " *.013 .032 57
The above results show that after about four months, the ,
amount of sulfur oxidized was generally about G0 per cent of
the total quantity present. regardless of whether 100 or 500
pounds per acre had been added. `