Measuring Soil Microbial Activity

Middle School High School Undergraduate

This activity examines how soil microbes, such as bacteria and fungi, are involved in carbon cycling. Students design experiments to explore the relationship between microbial respiration rates and soil variables such as temperature, habitat, soil type, and agricultural management choices. Four methods for measuring CO2 released from soil are provided, one in the field (CO2 probe), and three in the lab (CO2 probe, bromothymol blue (BTB), and acid-base titration).

Get the Guide Download the Full Package




Earth Science

Environmental Science

Physical Science

Carbon Cycle & Climate Change


Decomposition, respiration, carbon sequestration, climate change, microbial ecology, soils, carbon cycle, data analysis, scientific argumentation

Familiarity with the components of experimental design, data collection and data analysis. Basic understanding of cellular respiration, carbon cycle, role of soil microbes in ecosystems, and role of CO2 as a greenhouse gas.

Varies by technique and experimental design. Two to seven 50-minute class periods spread out over a one to two week period.

Varies depending upon activity. See activity description for details. Basic lab method requires either, BTB (bromothymol blue), CO2 probe or NaOH titration set-up. Field method requires CO2 probe and chamber constructed from 5-gal. bucket or similar vessel.