108 Proceedings of Indiana Academy of Science. 
TABLE V. 
Average Percent 6 and 7-Day Counts are of 10-Day Counts. 
(Silt Loam Subjected to Different Systems of Soil Management.) 
Time oF INCUBATION 5 7 19 Days* 
1 41.9% 100.0% 100.9% 
Clean Cultivation 2 27.2 97.3 100.0 
me 23.5 100.0 100.0 
_ 1 42.3 82.3 100.0 
Sod 2 41.5 78.8 100.0 
he 33.3 79.0 100.0 
; 1 65.1 85.3 100.0 
Straw Mulch 2 55.2 87.4 100.0 
“3 65.2 81.7 100.0 
1 67.3 88.2 100.0 
Light Grass Mulch 2 58.3 96.9 100.0 
ax ee 37.0 82.2 100.0 
Meeauge Rn Some ewe eee 46.5 88.3 100.0 
Average Clean Cultivation............|......... 30.9 99.1 100.0 
Se DOG, cocoon ee eee Oe eel See ae yee 39.0 80.0 100.0 
"Average Straw Mulch...............-0|..c.0000- 61. 84.8 100.0 
Average Light Grass Mulch...........]......... 54.2 89.1 100.0 
Table V shows: 
1. The rate of development of colonies varies with the system of 
soil management. 
2. Those conditions which unify differences in soil aeration are 
present where the rates of development of colonies check 
closest. 
3. Short periods of incubation would not show the relative num- 
bers of bacteria actually present in the soils. 
Many sets of plates have been counted after twelve and fifteen days’ 
incubation, but very rarely have counts increased at all after ten days’ 
incubation. With suitable media the counts obtained after seven days’ 
incubation have uniformly shown the comparisons between samples, and 
this does not mean that the increases from seven to ten days are numer- 
ically or proportionately the same. 
