Burrowing and casting activities of three endogeic earthworm species affected by organic matter location

International audienceEarthworms are crucial for production and maintenance of soil structure and their activities can stronglyimpact soil functioning (e.g. water regulation, nutrient dynamics). This laboratory study investigatedthe bioturbation activity of three endogeic species, Allolobophora chlorotica, Allolobophora icterica andAporrectodea caliginosa, as affected by different locations of organic matter (OM) in the soil profile: OMscattered on the soil surface (surface-OM) or homogeneously mixed into the soil (mixed-OM). Micro-cosms, each containing a combination of one species (three individuals) and one OM location, weresubjected to controlled environmental conditions (temperature, humidity and day/night cycle) for 60days. At the end of the experiment, microcosms were cut into multiple horizontal cross-sections everycentimetre and bioturbation activities were analyzed based on the number of burrows, the burrowedarea and the percentage of burrowed area totally refilled with casts.Results showed that regardless of species, there was significantly fewer burrows and a greater percent-age of burrowed area refilled with casts under mixed-OM than under surface-OM. A. chlorotica and A.caliginosa had a significantly greater burrowed area under mixed-OM than under surface-OM. Regardlessof OM location, as depth increased, burrow number and area decreased for A. chlorotica and generallyincreased for A. icterica. In contrast, burrowing activity of A. caliginosa was affected by OM location asdepth increased: under mixed-OM, burrow number decreased but burrowed area remained constant,whereas under surface-OM, burrow number remained constant and burrowed area increased.These results improve understanding of effects of endogeic species on soil structure and highlighteffects of OM location on earthworm bioturbation. Especially this study gives information about theburrowing activity of A. icterica which has so far been little documented, and also informs about refilledburrows which is a major parameter for soil functioning

Relevance Of Reduced Tillage Practices On Soil Biological, Chemical And Physical Quality And Ecosystem Services Under Organic Farming Context In Britany

Avoiding or limiting ploughing under organic farming management remains a big challenge for organic farmers. By developing an holistic approach, the aim of this study was to evaluate the impact, under organic farming management, of different tillage techniques on soil biological, physical and chemical quality and ecosystem services. In an experimental site located in Britany (France) four tillage techniques were compared: conventional ploughing (CP), agronomic ploughing (AP), superficial non-inversed tillage (C15) and very superficial non-inversed tillage (C8). Results, obtained during 10 years (from 2003 to 2013), showed a strong temporal variability between years, however some results appeared consistent. Positive impact of reduced tillage on hydraulic conductivity and organic matter content was limited to the 0-5 cm depth. No-inversed tillage (C15, C8) and agronomical ploughing (AP) significantly improved microbial biomass. C8 is the only technique which significantly decreased nematofauna. Earthworm biomass significantly decreased under conventional ploughing (CP) due to the decrease of anecic species while ploughing techniques (CP, LA) preserved total earthworm abundance due to endogeic species. Endogeic species had a negative impact on hydraulic conductivity whereas anecic enhanced the conductivity and Carbon and Phosphorus contents. No-inversed tillage techniques (C8, C15) leaded to a decrease of the crop yield, due to an increase of weeds which increased water and nutritive competition. This study highlighted the interests and limits of no-inversed techniques and agronomical ploughing applied in organic farming management for enhancing soil quality and crop yield

A 3-Dimensional description of cracks networks in clayey soils, using image analysis and a structural model

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Evolution des reseaux de fissures lors du retrait d'un sol argileux

National audienc

Analyse des retraits volumique et lineaire d'un sol argileux glauconieux; aspects physiques et morphologiques. Compte-Rendu d'AIP

*INRA, Science du Sol; Rennes Diffusion du document : INRA, Science du Sol; RennesNational audienc

Contribution à l'étude du fonctionnement du drainage: caractérisation et comparaison de la tranchée (draineuse-traineuse) et de la saignée (draineuse sous-soleuse) de drainage

National audienc

La fissuration d'un sol argileux au cours du dessechement. II : Modelisation morphologique

National audienceStudy of the structural consequences of the shrinkage of a clayey soil has led us to propose a three-dimensional morphological model. This model computes the width and the spacing of the different types of cracks from known variables, i.e. mass and bulk density of the structural elements, and thickness of soil layers. It accounts quantitatively for the existence of 2 processes that follow one another during drying : splitting up and sintering. We describe 2 kinds of networks (micro- and macrocracks) which differ not only in their morphology, but also in the way in which they develop during shrinkage. Then, by calculation of the void ratio for each kind of cracks, we propose an assessment of soil porosity.L’étude des conséquences structurales du retrait d’un sol argileux conduit à proposer un modèle morphologique tridimensionnel. Il permet de calculer les composantes fissurales (largeur et écartement des divers types de fissures) à partir des variables connues (masse et masse volumique des éléments structuraux, épaisseur des couches de sol). Cette analyse confirme que 2 processus se succèdent au cours du dessèchement : la fragmentation et la prise en masse. On décrit ainsi 2 types de réseaux (micro- et macrofissures) qui se distinguent non seulement par leur morphologie, mais également par leur évolution durant le retrait. Enfin, en calculant l’indice des vides pour chaque fraction porale, on propose un bilan de porosité du sol

Aspect tridimensionnel de la deformabilite des materiaux argileux gonflants. Mise en evidence de l'anisotropie du retrait.

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