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Soil Atmosphere as Influenced by Temperature and Moisture¹

ABSTRACT

Composition of the atmosphere of Yolo sandy loam soil columns was determined at different depths and different soil moisture conditions. After saturation with water, soil columns were placed in 30, 25, 20, 15, or 10C constant temperature rooms and moisture was allowed to evaporate from the soil surface. Soil moisture content was determined with a gamma-ray densitometer; CO₂, O₂, and N₂ concentrations were determined by gas chromatography. After 14 days at 30C, moisture tension at the 65 cm depth was 0.1 bar and the soil atmosphere contained 17% CO₂ and 4% O₂. At the 35-cm depth, the moisture was 0.3 bar and the CO₂ and O₂ concentrations were 7% and 14%, respectively. At the 5-cm depth the CO₂ did not rise over 1.5%. At lower temperatures the CO₂ did not rise over 1.5%. At lower temperatures the CO₂ concentrations were less and the maximum was reached more slowly. However, the N₂ concentration increased to almost 90%. At each temperature and all depths, rapid changes occurred in the concentration of gases when the soil moisture tension reached 0.10 to 0.15 bar.

¹ Contribution from the Department of Vegetable Crops, University of California, Davis. Presented before the Western Society of Soil Science, June 15, 1966, at Seattle, Wash.

² Olericulturist, Associate Olericulturist, and Associate Olericulturist, respectively. The technical assistance of George Zimmerman, Robert Thompson, and Paul Juncker is gratefully acknowledged.

Received for publication August 15, 1966. Accepted for publication September 22, 1966.