Differential Effects of Soil Water Content and Temperature on Nitrification and Aeration
- G. L. Grundmann ,
- P. Renault,
- L. Rosso and
- R. Bardin
Laboratoire de Biologie Alpine, Université Joseph Fourier, BP 53x 38041, Grenoble Cédex, and Laboratoire d'Ecologie Microbienne du sol, URA CNRS 1450, Université Claude Bernard Lyon I, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne, Cédex, France
INRA, Unité de Science de Sol, Domaine Saint-Paul, B.P.91, 84143 Montfavet Cédex, France
Laboratoire de Biométrie, URA CNRS 243, Université C. Bernard, Lyon I, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne Cédex, France
Laboratoire d'Ecologie Microbienne du Sol, URA CNRS 1450, Université C. Bernard, Lyon I, 43 Bd du 11 Novembre 1918, 569622 Villeurbanne Cédex, France
Environmental concerns have stimulated increased interest in NO−3 accumulation in soils. The aeration status of the soil, which is mainly governed by the water content and temperature, is a central factor. The biological process responsible for NO−3 accumulation, nitrification, was measured to estimate the combined effects of water content and temperature and determine their joint effect on soil aeration. The effects of temperatures of 15, 20, 25, 30, and 35°C and water contents equivalent to 0.35, 0.42, 0.50, 0.52, 0.57, and 0.60 relative water content (volumetric water content/total porosity) on the nitrification activity of soil samples containing 2-mm sieved soils taken at 0 to 20 or 20 to 40-cm depth were determined by measuring NO−3 accumulation for 17 h. A descriptive model including three biological parameters, maximum nitrification rate (Nrmax), optimal relative water content (Θopt), and temperature, was developed. Maximum Nrmax occurred at 25.5°C in 0- to 20-cm soil and at 20°C in 20- to 40-cm soil, suggesting an adaptation of soil nitrifying populations to the temperature regime of the soil. The Nrmax value was negatively related to Θopt, and Θopt was dependent on temperature (T). This Θopt (T) relationship was parabolic in nature, with Θopt being at a minimum between 20 and 25°C. It could be simulated using O2 diffusion and respiration rates, inferring that these processes influenced Θopt and T correlation. The ranges of O2 concentrations favorable to maximum nitrification within an aggregate volume fraction were estimated for different temperatures. Nitrification was generally maximum when the intraaggregate pore spaces were saturated with water, with no water in the interaggregate pore space (i.e., 0.44 relative water content at 25°C and 0.36 at 20°C at 0- to 20- and 20- to 40-cm depths).
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