298 Proceedings of Indiana Academy of Science 
amount of nitrates present. Although the accuracy of this method has 
been severely criticized it is the one most widely used and most prac- 
tical for this type of work where comparative rather than absolute 
results are sought. 
A one hundred gram aliquot of soil was weighed into tumblers 
marked for the respective plots 1A to 13A. Each tumbler was covered 
with a petri plate lid and set away in a locker. After two weeks incu- 
bation nitrates were determined as before. 
One hundred grams of each sample were placed in tumblers marked 
1B to 13B and one cubic centimeter of a ten per cent solution of am- 
monium sulphate was dropped over the soil in each tumbler. They 
were covered and incubated two weeks then tested as in the case of 
the fresh nitrates. In the case of both incubated samples when too 
dry equal amounts of distilled water were added to each tumbler or 
if too wet the covers were left off of each tumbler for equal periods 
until of the proper moisture content. 
Duplicate plates were made of dilutions 1 : 100,000 and 1 : 1,000,000 
from each sample. A 1 : 10,000 dilution was also plated for a few of 
the tests but the colonies were too crowded to make the count accurate. 
Several different media recommended by soil bacteriologists were tried 
in an effort to determine which of them would give the best growth 
of bacteria and not encourage the spread of molds over the plates. The 
following synthetic agar media seemed most satisfactory and was used 
through the major part of the investigation: 
5 grams of sodium potassium tartarate; 
.) gram of di-basie potassium phosphate; 
1 gram of peptone; 
.2 gram of magnesium sulphate; 
15 grams of agar; 
1 liter of distilled water. 
The plates were incubated for one week at room temperature be- 
fore counting colonies of bacteria and molds. However, in two instances 
low temperature in the room deterred growth so that they were in- 
cubated longer. 
TABLE 2. 
Moisture Percentage. 
Plot | 
No. | Mar. Apr. May June July Aug. | Sept. Oct. Nov. Total Ave. 
| | | | 
1 23.65 21.25 10.60 | 13.24 | 14.49 18.89 20.83 | 165.21 18.35 
2 25.15 22.77 14.39 | 16.34 13.01 20.17 22.60 | 164.59 18.29 
3 24.26 22.95 |} 12.48 15.68 15.93 24.82 21.79 | 168.36 18.70 
4 24.38 | 22.05 | 12.65 | 15.55 15.84 20.97 29.11 | 174.48 19.39 
5 23.32 21.60 8.86 | 15.55 13.93 21.61 20.21 | 153.59 17.07 
6 24.00 | 20.75 12.88 15.13 15.25 | 20.92 21.53 | 158.91 17.66 
u 23.62. | 21.55 12.30 | 15.74 / 16.46 21.53 21.01 | 163.59 18.17 
8 23.84 | 21.05 12.40 | 14.17 | 14.17 20.73 20.52 | 155.93 17.32 
9 23.40 21.85 11.65 14.38 14.32 20.02 20.03 | 154.84 17.20 
10 23.14 20.45 12.75 14.17 14.01 20.23 20.38 | 153.30 17.03 
11 21.76 20.40 10.75 13.76 13.70 20.01 19.92 | 145.37 16.15 
12 23.15 20.45 10.70 13.57 12.94 20.26 19.80 | 148.42 16.50: 
13 22.85 20.25 11.58 13.48 13.15 20.78 20.77 | 151.38 16.82 
Total] 306.52 | 277.37 153.90 | 190.77 | 187.20 | 270.94 | 278.50 |........ 226.43 
Ave 23.58 21.33 11.84 14.67 14.40 20.84 21.42 | 158.32 17.45 
