772 
Journal of Agricultural Research 
Vol. V, No. 16 
EFFECT OF ELEMENTAL SULPHUR AND SULPHATES ON SOIL 
BACTERIA 
MIXED CULTURES 
For these experiments ten i-gallon jars containing 2 kgm. each of 
Miami silt loam taken from the Wisconsin Experiment Station farm 
were used. The analysis of this soil is as follows: 
Per cent. 
Potassium. 2.16 
Nitrogen.15 
Phosphorus....15 
Sulphur.016 
Calcium carbonate..33 
Humus. 1. 38 
The moisture content of the soil was held at 18 per cent, or about half- 
saturation. Each jar was covered with a layer of cotton and gauze to 
prevent contamination, and was incubated at 28° C. Various amounts 
of sulphur and of calcium sulphate were added to the pots, as shown in 
Table I. At definite intervals samples were taken from the jars and 
bacterial counts as well as determinations of ammonia and of nitrates 
made. The results of the latter are given in Table I. 
Table I .—Effect of calcium sulphate and elemental sulphur on soil bacteria 
Number of organisms per gram of soil after— 
x realm enx. 
12 days. 
30 days. 
44 days. 
72 days. 
93 days. 
Untreated. 
Given 0.01 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 caldum sulphate_ 
Untreated. 
Given 0.01 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. 
6,866,000 
6,866,000 
8,506,000 
7,221,000 
8,290,000 
8,580,000 
6,590,000 
7,429,000 
9,106,000 
8,290,000 
8,864,000 
6,504,000 
8,746,000 
10,544,000 
14,140,000 
7,923,000 
8,029,000 
9,585,000 
9, 166 ,000 
8,746,000 
8,866,000 
8,208,000 
11,020,000 
7,070,000 
10,790,000 
13,900,000 
13,789,000 
13,060,000 
13,420,000 
12,938,000 
8,626,000 
8,866,000 
10,065,000 
10,300,000 
4,914,000 
2,635,000 
6,350,000 
6,590,000 
8,028,000 
7,923,000 
7,548,000 
7,668,000 
6,949,000 
7,923,000 
7,668,000 
6,590,000 
3,594,000 
2,329,000 
10,782,000 
11,026,000 
9,945,000 
9,824,000 
10,305,000 
9,945,000 
9,705,000 
8,626,000 
8,116,000 
8,866,000 
2,995,000 
719,000 
The data show that calcium sulphate in the quantities used apparently 
has little effect on the number of soil organisms. Elemental sulphur, 
however, decreases the number of soil organisms that grow on agar 
plates. This decrease is not noticed until after 44 days, and only in soils 
to which 0.05 and 1 per cent of sulphur had been added. Quantitative 
acidity tests of the soils of these two jars showed it to be distinctly acid. 
This is corroborated by the work of Lint, * 1 who has shown that in soil 
elemental sulphur is oxidized to sulphate and that the acidity produced 
is proportional to the amount of sulphur added. Acidity determination s 
were made according to Truog’s 2 method and are given in Table I I. 
1 Lint, H. C. The influence of sulphur on soil acidity. In Jour. Indus, and Engin. Chem., v. 6, no. 9, 
p. 747 - 748 * 1914* 
1 Tfuo g, E* A new test for soil acidity. Wis. Agr. Exp. Sta. Bui. 349.16 p., 3 fig., 1 pi. 1915. 
