774 
Journal of Agricultural Research 
Vol. V, No. 16 
appreciable effect on nitrification. It should be noted that while the 
bacterial counts begin to decrease after 44 days, the ammonia content 
begins to increase at this time. 
Table IV. —Effect of calcium sulphate and elemental sulphur on nitrate production in 
the soil 
Quantity (in milligrams) of ammonia nitrogen per ioo 
gm. of soil after— 
Treatment. 
Untreated. 
Given o.oi per cent of calcium sulphate_ 
.05 per cent of calcium sulphate_ 
.10 per cent of calcium sulphate_ 
.50 per cent of calcium sulphate_ 
1.00 per cent of calcium sulphate_ 
Untreated. 
Given o.oi per cent of sulphur. 
.05 per cent of sulphur. 
.10 per cent of sulphur. 
.50 per cent of sulphur. 
1.00 per cent of sulphur. 
12 days. 
30 days. 
44 days. 
72 days. 
93 days. 
1.87 
i -34 
2.95 
3-93 
4. 70 
2.12 
i- 25 
2-35 
4*13 
5-07 
2.42 
1.01 
2.49 
4-58 
5-72 
1.14 
1.25 
2.10 
4-03 
5-47 
1.86 
1-23 
2-45 
2.92 
4.99 
i -35 
1.82 
2-39 
2.87 
4 - 5 i 
1-53 
1.66 
2-93 
3-93 
4*35 
1.80 
1.99 
2.65 
3-13 
4-13 
2.17 
1.88 
2. 29 
3- 20 
4 - 53 
1.38 
1. 69 
2. 92 
4 -13 
4 - 93 
1.24 
•54 
1.41 
1.14 
.89 
•94 
•54 
.64 
•95 
•85 
PURE CULTURES 
In order to determine the effect of calcium sulphate on pure cultures 
of legume bacteria (red clover), Ashby’s solution, minus the sulphate, was 
used. To 100 c. c. portions of this solution in 10 large Erlenmeyer flasks 
were added 30 gm. of pure quartz sand and various amounts of calcium 
sulphate. The sand was used to aid in breaking up the aggregates of 
bacteria when samples were taken for counts. All cultures were incu¬ 
bated at 20 0 C., and at intervals of one and two weeks bacterial counts 
were made. The results of these counts are given in Table V. 
Table V. —Effect of calcium sulphate on the growth of red clover organisms in Ashby*s 
solution 
Treatment. 
Number of organisms per cubic centimeter 
of solution after— 
oday. 
7 days. 
14 days. 
Untreated. 
30, OOO 
30, 000 
30, OOO 
30, OOO 
30, OOO 
53, OOO, OOO 
139, OOO, OOO 
177, OOO, OOO 
198, OOO, OOO 
12 1, OOO, OOO 
157, OOO, OOO 
425, OOO, OOO 
400, OOO, OOO 
450,000,000 
350, OOO, OOO 
Given 0.01 per cent of calcium sulphate. 
.02 per cent of calcium sulphate. 
.05 per cent of calcium sulphate. 
.10 per cent of calcium sulphate. 
The data show that the numbers of bacteria that grow on Ashby’s agar 
were increased by the addition of calcium sulphate. The increase is 
very marked after both 7 and 14 days. It should be noted that 0.01 per 
cent of calcium sulphate is apparently just as efficient in producing an 
increase in the number of bacteria as is 0.1 per cent. This seems to 
indicate that only a trace of calcium sulphate is needed to stimulate 
the legume bacteria. 
