Mar. 6 ,1917 
Fermentation of Corn Silage 
375 
RISE IN TEMPERATURE 
Another characteristic phenomenon of silage fermentation, but one 
very much misunderstood in the early days of silage making, is the rise 
in temperature of the silage. Temperatures as high as 130° F. have been 
observed in the silo at or near the surface of the silage. This excessive 
heating is due to activity of microorganisms greatly accelerated by the 
presence of atmospheric oxygen, and occurs whenever silage is uncovered 
and left exposed to the air for a time. The temperature deep in the silo, 
however, protected from the air and sufficiently removed from the con¬ 
duction of heat from 
the surface of the si¬ 
lage, is rarely higher 
than 8o° to 90° F. It 
is rather unsatisfactory 
to attempt to obtain 
curves characteristic 
of bacterial or enzymic 
fermentation from the 
rise in temperature of 
the medium, on ac¬ 
count of the number of 
somewhat extraneous 
factors involved. The 
outside temperature is 
always a factor, and 
the rise in temperature 
of the silage might 
easily affect the rate of 
chemical reactions or of bacterial growth, thus increasing the rate of 
temperature rise and perhaps changing the nature of the curve. 
Data which have been obtained from the farm silos 1 and from very 
carefully insulated laboratory silos suggest that the greater part of the 
heat developed is due to microbial action. It is considered unnecessary 
to reproduce these data here, as similar data have been published (14). 
However, one table is subjoined (Table IX) showing the rise in tempera¬ 
ture at the surface of the silage in one of the farm silos. An iron pipe 
was forced down into the silage for about 4 feet, and a thermometer, 
immersed in a test tube full of water, lowered into the pipe so that the 
bulb was 2 feet below the surface of the silage. The top of the pipe 
was closed except when the thermometer was pulled up for reading. 
These data when plotted give a smooth and typical bacterial fermentation 
curve. Of course, this does not exclude the possibility of some heat 
production by enzym action. 
1 With the cooperation of the Agricultural Engineering Section of the Iowa Station. 
78365 °— 17 -- 2 
DAYS 
Fig. 10.—Curve showing the increase in amino nitrogen in series 4 
