304 
Journal of Agricultural Research 
Vol. XXIV, No. 4 
culture media containing soluble carbonates or bicarbonates or blacl< 
alkali soil; the elemental sulphur will be oxidized only comparatively 
slowly, but, in the presence of T. thiooxidans this oxidation will be 
rapidly hastened and the reaction quickly changed to any degree of 
acidity, depending merely on the quantity of sulphur used. 
The possibility of the participation of other organisms oxidizing sulphur 
or sulphur compounds in the soil, or in any way influencing the process, 
in addition to the two mentioned, is not excluded. Neither is the possi¬ 
bility excluded that the oxidation of sulphur in alkaline soil is carried 
on chiefly by a strain of Thiohacillus thiooxidans which has adapted itself 
to alkaline conditions. While T. thiooxidans grows vigorously on arti¬ 
ficial media and does not deteriorate with age, Thiohacillus B rapidly 
deteriorates under cultural conditions and the very slow oxidation of 
sulphur by this organism, particularly in the latter part of the work, may 
be due to this phenomenon. 
SUMMARY 
(1) The use of sulphur in the presence of the proper sulphur-oxidizing 
bacteria will result in the transformation of black alkali soil to white 
alkali soil. 
(2) The final reaction of the soil depends on the quantity of sulphur 
used and the length of time which the sulphur is allowed to be in con¬ 
tact with the soil. 
(3) The oxidation of sulphur in black alkali soil is probably carried 
on by the agency of more than one sulphiu'-oxidizing bacterium. 
(4) In the presence of two bacteria, one of which can act upon sul¬ 
phur under distinctly alkaline conditions while the other rapidly oxid¬ 
izes sulphur under acid conditions, the speed of the reaction is greatly 
hastened. 
