jan. 17,1916 Effect of Sulphur and Calcium Sulphate on Plants 779 
held at 18 per cent. After four weeks these were seeded with red clover 
and inoculated with a pure culture of red-clover organisms. Two 
weeks later the number of plants was reduced to six per jar. There 
was no appreciable difference in the size of the plants until the fourth 
month. At this time those in the sulphur series showed an increase in 
growth. At the end of the fifth month this increase was more marked. 
The leaves of the plants in the jars to which 0.05 per cent of sulphur 
had been added were tinged with red at the edges. The stem also 
showed this red coloration, but to a lesser degree. At the end of the 
. fifth month the tops were cut and weighed, green and dry, with the 
results shown in Table X. 
Table X .—Effect of elemental sulphur on the growth of red clover 
Treatment. 
Weight of crop. 
Green. 
Dry. 
Untreated.. 
Gm. 
25-3 
32.6 
29.4 
30. 8 
34-0 
Gm. 
6 . 25 
6. 90 
6- 75 
6. 80 
7 . OO 
Given .01 per cent of sulphur.. 
.02 per cent of sulphur.. 
.05 per cent of sulphur.... 
.10 per cent of sulphur. 
The sulphur series showed a slight increase in yield. Several of the 
plants died, so that the number of plants in the various jars varied. 
The results therefore are not final. It seems safe, however, to say that 
sulphur increased slightly the yield of clover in Miami silt-loam soil. 
After the tops were cut the roots were carefully removed and washed. 
There was no apparent difference in the size or the number of nodules 
in the treated and the untreated series. All of the roots contained a 
great number of nodules. 
SUMMARY 
(1) Calcium sulphate, when added to a soil, apparently has no marked 
effect on the total number of bacteria that grow on agar plates; nor does 
it produce any marked increase in ammonification or nitrification. This 
confirms the observations of Fred and Hart. 1 
(2) Targe amounts of elemental sulphur cause a decrease in the total 
number of bacteria that grow on agar plates, but produce an increase in 
ammonification at concentrations of 0.05 per cent. This increase in 
ammonia is accompanied by a parallel decrease in nitrate formation. 
The decrease is very probably due to the acidity or toxicity produced by 
the oxidation of sulphur. 
1 Fred, E. B., and Hart, E. B. The comparative effect of phosphates and sulphates on soil bacteria. 
Wis. Agr. Exp. Sta. Research Bui. 35, p. 35-66, 6 fig. 1915. 
