Organic Matter Decomposition as Influenced by Oxygen Level and Flow Rate of Gases in the Constant Aeration Method

Laboratory experiments were conducted to determine the rate of decomposition of wheat straw added to soil when continuous aeration was conducted with N 2 ‐O 2 gas mixtures containing 0, 0.5, 1.0, 2.5, 5.0, and 21% oxygen at flow rates of ⅛, ¼, ½, 1, and 2 liters per hour. Rates of decomposition and total decomposition were followed by determination of wheat straw carbon evolved as CO 2 . Total decomposition at all oxygen levels varied directly with aeration flow rate, except for the 0% level where an inverse relationship was observed. Microbial activity at the 21% oxygen level was greatly stimulated as flow rate increased from ⅛ through 2 liters per hour. A rapid increase in microbial activity occurred for the 0.5, 1.0, 2.5, and 5.0% oxygen levels as flow rate increased from ⅛ through ½ liters per hour, however, little increase in CO 2 production was observed at higher flow rates.