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THESE Maha DEEB Influence des plantes, des vers de terre et de la matière organique sur la structure de Technosols construits

Abstract : Constructed Technosols are mixtures of technogenic materials used to create a new soil dedicated to growing plants. Constructed Technosols provide an opportunity to recycle and optimally use urban waste, and are an alternative to the use of agricultural soils for producing urban soils. This work is assessing in particular the influence of the OM levels and interactions with earthworms and plants on the physical properties of Constructed Technosols. The materials used to build our Technosols are compost and excavated deep horizons. In a first experiment, we tested the influence of OM rates on hydrostructural properties of Technosols, realizing 6 mixtures of increasing volume proportions of compost (0 to 50%). The shrinkage and retention curves show that the hydrostructural properties of Technosols are similar to those of natural soils. Increasing the amount of organic material is accompanied with a positive effect on micro and macro porosity, as well as on the water available for plants. Secondly, these mixtures were incubated in a growth chamber with or without earthworms (Aporrectodea caliginosa) and with or without plants (Lolium perenne). After 5 month of experiment, we measured hydrostructural properties, aggregation, and distribution of carbon in each fraction. The presence of plants and / or earthworms explains 19% of the variance of hydrostructural properties of the soil, and compost dose affects 14%. The interaction between organisms and compost further explains the variance (40%) than the effects of these individual factors. Compost and plants play a positive role in the available water by acting on both macroporosity and microporosity, while earthworms play a positive role only on the latter. Furthermore, the proportion of aggregates >3 mm is more important in the treatments control and earthworms, while the proportion of aggregates <3 mm is greater in the presence of plants, regardless of the presence of earthworms. Organisms have a stronger effect on the structural stability (77%) than compost (4%). All have a positive effect on the amount of Corg in the different fractions of aggregates. Finally, mineralization of Corg increases in the presence of worms or compost, but decreases in the presence of plants. Our results demonstrate the interest of enhancing urban materials such as excavated deep horizons and compost to build Technosols. A summary of the results allows us to recommend a volume content of compost between 20 and 30% for a good structure, without increasing much the cost induced by compost. Noting the positive effect of earthworms, plants and earthworms/plants interactions on porosity, structural stability and carbon storage, it seems appropriate to favor their presence or plan their introduction as soon as possible.
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Maha Deeb. THESE Maha DEEB Influence des plantes, des vers de terre et de la matière organique sur la structure de Technosols construits. Sciences de l'environnement. Paris Est, 2016. Français. ⟨tel-02429734⟩

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