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Evolution et effets sur la structuration du sol de la matière organique apportée en grande quantité

Abstract : The RECONSTITUTED ANTHROPIC SOILS are defined as strongly modified by the human activities, and built from natural or transformed materials. The spatial and temporal variability of their physical properties is important, and they are characterized by the incorporation of great organic matter quantities. The organic matter decomposition and its influence on structuration and hydraulic properties were studied. Three organic products (green wastes compost, sewage sludge and woodchips compost, and sphagnum peat) were mixed by 20 or 40% (by volume) with a sandy loam, let in a 600L boxe under natural conditions during two years. Samples were taken 5, 12 and 24 months after the beginning of the experiment and the decomposition of the organic matter was measured (C rates, physical fragmentation, biochemical composition and mineralization potential), the mixtures structuration (bulk density, pore space and structural stability) and their hydraulic properties (retention curve and saturated hydraulic conductivity). The results show decreases in the organic matter quantities, with important modifications of the biochemical composition characterized by increases in solubles rates, and a decrease of the lignin in the coarse organic matter fractions. For the composts / sandy loam mixtures mineralization potential of the added organic matter decreases. For the peat / loam mixtures, mineralization potential increases, and the results show a decrease of the peat organic matter stability. A model describing the evolution of the organic matter quantities was proposed and its parameters were fitted under controlled and natural conditions. As the organic matter decays, important effects were measured on the compost / loam mixtures structuration, with an increase of the structural stability and a pore space reorganization. The creation of a macroporosity is as much important as it is made from elongated and winding pores, that are involved in the hydodynamic behaviour. The mixture structuration mecanism of the compost / loam mixtures backes up with the water retention and the saturated hydraulic conductivity improvement. The image analysis results are coherent with the van Genuchten model, fitted on the retention curves. On the contrary any effect of the sphagnum peat was measured on the mixture structuration. If immediate effects of the organic matter incorporation were similar, composts involved a structuration mechanism in 24 months, while the sphagnum peat had no effet. The most interesting results for structuration were obtained for the 40% composts doses.
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Submitted on : Monday, May 31, 2010 - 2:08:16 PM
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  • HAL Id : tel-00487882, version 1
  • PRODINRA : 247953


Claire Grosbellet. Evolution et effets sur la structuration du sol de la matière organique apportée en grande quantité. Autre. Université d'Angers, 2008. Français. ⟨tel-00487882⟩



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