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This article in SSSAJ

  1. Vol. 62 No. 3, p. 553-563
     
    Received: Jan 28, 1997
    Published: May, 1998


    * Corresponding author(s): pierre.renault@avignon.inra.fr
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doi:10.2136/sssaj1998.03615995006200030001x

Air Pressure Fluctuations in a Prairie Soil

  1. Pierre Renault ,
  2. Dalila Mohrath,
  3. Jean-Claude Gaudu and
  4. Jean-Claude Fumanal
  1. INRA, Unité de Science du Sol, Domaine St-Paul, Site AgroParc, 84914 Avignon Cedex 9, France
    IUT de Marseille St-Jérôme, Dépt. Mesures Physiques, 142, traverse Susini, 13388 Marseille Cedex 13, France

Abstract

Abstract

The influence of air convection on soil aeration has not been investigated in great detail. A study was conducted to measure air pressure changes by depth in the first 2 m of a prairie soil that was known for its denitrification properties. An absolute air pressure probe was used to measure air pressure fluctuations at the soil surface and newly designed differential air pressure probes were placed at depths of 0.1, 0.2, 0.3, 0.4, 0.5, 0.75, 1, 1.5, and 2 m. A procedure of in situ recalibration was used every 6 or 7 wk for these probes. At the same depths, capacitive probes and thermocouples measured the volumetric water content and temperature, respectively. The bulk density profile, water table level, and rainfall amounts were recorded. The atmospheric pressure ranged between 97 000 and 101 000 Pa during the experiment. The signal drift of the air pressure probes was negligible for four of the probes and <50 Pa for the others. The accuracy of the measurements with signal drift compensation was superior to 10 Pa. Differences of air pressure between the soil at the surface and at depth may be >2000 Pa. These differences, which are not necessarily linked to the depth, are probably due to soil heterogeneities and generally to water infiltration. Air pressure seemed to level out quickly when the air-filled pore space was continuous. This generally prevented “dephasing-amortization” effects. When the air-filled pore space was discontinuous, differential air pressures depended simultaneously on the atmospheric pressure and temperature fluctuations.

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