The moist soil mixtures were transferred into plastic containers, tapped
and patted to produce a consistent bulk density (~1.2 g cm−3) across
the C addition treatments. We set up each experimental unit in 1.2 L
sealed plastic containers, which held three small containers: a 200 mL
container with the soil mixtures, a 70 mL jar containing NaOH (2.5 M)
to capture CO2 emanating from soil mixtures and a 70 mL jar with
40 mL of DI water as a humidity control.