Oxygen deficiency negatively affects crop yield and has a major impact on soil biological activity. This work was performed to ascertain the factors affecting the O 2 concentration in a soil profile, and to analyze the hypothesis used in O 2 transport models. Oxygen concentration was measured using platinum microelectrodes. Soil porosity, water content, temperature, groundwater depth, and microbial respiration were analyzed as the driving variables affecting O 2 concentration. Soil respiration was well described by a Michaelis kinetics; the maximal rate of respiration for the 0‐ to 0.1‐m layer (2.5 × 10 ‐5 mol m ‐3 s ‐1 ) was five times higher than for the 0.3‐ to 0.5‐m layer. This implies that the simplification of vertical homogeneity and zero‐order kinetics for O 2 consumption are invalid to estimate O 2 transport. In the topsoil, the amplitude of the changes in O 2 concentration after rainfall decreased in the order autumn > winter > summer. At 0.2 m for rainfall of ≈40 mm, the O 2 concentration decreased 0.09 m 3 m ‐3 within 3 d after rainfall in autumn, and 0.05 m 3 m ‐3 within 6 d in winter. The fluctuations observed in O 2 concentration after rainfall indicated that the steady‐state approximation used in models is too restrictive to describe O 2 transport in soil. In the subsoil, O 2 concentration varied slightly due to low O 2 consumption (≈10 ‐7 mol m ‐3 s ‐1 ). Oxygen concentration in the topsoil was negatively associated with the water‐filled pore space, except for measurements taken immediately after rainfall >30 mm d ‐1 , which indicated the presence of entrapped air. This suggests that the hypothesis of instantaneous equilibrium between water content and soil O 2 concentration is a reasonable simplification except for the 12‐ to 24‐h following high‐intensity rainfall.
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Sierra et al. (1998) studied this question.