Effective microorganisms or EM is a consortium of beneficial microorganisms (primarily photosynthetic
and lactic acid bacteria, yeast, actinomycetes, and fermenting fungi) that can be applied as inoculants to
increase the microbial diversity of soil. Two fields of sugar cane in the province of Tucumán, Argentina
were treated with either EM containing brewery fermentation tank residual yeast (YS) or just EM (NYS).
The outcome was 1000 kg Ha−1 less of sugar cane harvested from YS field. The aim of this work was to
analyze both soils to find outif calorimetry could assess the negative effect of yeast. Mass specific thermal
power–time curves were obtained during 100 or more h of measurement. Once a day, a vial containing
NaOH solution was introduced into the calorimetric ampoule to determine CO2 evolution. A plot of log
SMB (soil microbial biomass) as a function of log p gave a similar relation as previously reported for those
samples that showed an energy expenditure of 16–22 J cm−3 CO2 respired. Thus, soil microbial biomass
could be determined during microbial growth. Results showed that yeast suppressed the activity of part
of the soil microorganisms. Also, soil microbial activity increased with time in NYS due to successive
applications of EM.