Modeling oxygen and water flows in peat substrate with root uptakes

Abstract : Distribution and movement of liquids and gases in growing media present high specificity compared to in situ soil. This is due to the limited volume of susbtrate in which water and oxygen availability highly fluctuate over a short period of time (a few hours), and could rapidly lead to stress conditions. In order to improve our knowledge of the substrate-plant system, we first precisely characterized all transfer properties of a peat substrate (water retention, hydraulic conductivity, oxygen diffusivity and volume variation), during a drying-wetting cycle. All these characteristics were integrated into a one-dimensional transfer coupled model of water and oxygen, combining a macroscopic approach, Richards' equation, with a root function (water and oxygen uptakes). By imposing conditions close to those found in soilless production, our model allow us to follow the evolution of hydrodynamic and structural parameters of the substrate-plant system on a one-day time scale. If one replaces in the "not-limiting" range of water content, corresponding to a high hydraulic conductivity (theta > 0.45 m3 m-3) and a high oxygen diffusivity (&theta < 0.70 m3 m-3), our model underline that little changes in the initial conditions involve rapid decrease of water and oxygen content in the susbtrate. Consequently, it could lead to important and sustained water and oxygen stress conditions in the root vicinity.
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Rémi Naasz, Jean-Charles Michel, Sylvain Charpentier. Modeling oxygen and water flows in peat substrate with root uptakes. Proceedings of the International Symposium on Growing Media, Sep 2005, Angers (FR), France. pp.191-197. ⟨hal-00729768⟩

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