The soil mixture (300 g dry) was pl

The soil mixture (300 g dry) was placed in the bottom of a 2-L
(working volume) wide mouth jar (Ball Corporation, item #
383178). Distilled water was added to bring the moisture content of
the mixture to 60% of the moisture holding capacity. The test
specimens (1 g of sample carbon) were then mixed thoroughly into
the soil. A solution containing 20 ml of potassium hydroxide (KOH)
0.5 N (Fisher Scientific, PA, U.S.) was placed in a cup suspended
from the lid of each vessel to trap evolved CO2. All vessels were
sealed and incubated at room temperature (20  2 C).