11 research outputs found
Importance des composés phénoliques dans les interactions entre plantes et microorganismes : exemple des relations Rhizobium/légumineuses
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Meth@+.com - ModĂ©liser le dĂ©veloppement dâun systĂšme innovant de mĂ©thanisation collective et Ă hautes performances environnementales Ă lâĂ©chelle dâun micro-territoires.
En 2013, le plan Energie Méthanisation Autonomie Azote était publié, et un modÚle « français de
mĂ©thanisation agricole collective » Ă©tait appelĂ© Ă devenir lâun des leviers de la transition Ă©nergĂ©tique et
Ă©cologique. Les travaux prĂ©sentĂ©s ici ont Ă©tĂ© rĂ©alisĂ©s entre 2013 et 2016 et se sont appliquĂ©s Ă
explorer plusieurs composantes de ce modĂšle de mĂ©thanisation afin de cerner les stratĂ©gies Ă lâorigine
des schémas de méthanisation, et leurs implications environnementales et agronomiques. Ainsi assortie
dâun Ă©tat des lieux des pratiques agronomiques de 4 mĂ©thaniseurs, la connaissance des digestats a Ă©tĂ©
approfondie afin de permettre une meilleure prise en compte de leurs propriétés dans leur stratégie de
gestion des ressources. Les logiques associĂ©es aux flux de matiĂšres et dâĂ©lĂ©ments fertilisants en amont et en aval des installations de mĂ©thanisation ont ainsi Ă©tĂ© explorĂ©es afin dâĂ©tablir un cadre dâanalyse des stratĂ©gies de
gestion des ressources par les mĂ©thaniseurs. Lâapproche des implications agro-environnementale sâest
faite par lâĂ©tude de la valeur fertilisante et amendante de plusieurs sortes de digestats.
La valeur fertilisante azotée de 5 formes de digestats a donc été définie, mettant en évidence la forte
variabilitĂ© de lâintĂ©rĂȘt des digestats au regard de ce critĂšre, mĂȘme si lâammonium reprĂ©sente toujours la
grande majoritĂ© de lâazote total (>70%). Une biodisponibilitĂ© de 100% du phosphore des digestats a Ă©tĂ©
mise en évidence par traçage isotopique. La variabilité des propriétés amendantes des digestats a été
mise en évidence par application de fractionnement biochimique (ISMO 73±8%, n=19)), et par
minĂ©ralisation potentielle du carbone et de lâazote.
Ces travaux restent limitĂ©s par le nombre dâunitĂ©s de mĂ©thanisation suivies (n=3), et appellent
lâapprofondissement des tendances soulevĂ©es.In 2013, in France, the « Energie MĂ©thanisation Autonomie Azote » plan was published, and the
âFrench agricultural and collective biogas modelâ should become a lever of the energetic and ecological
transition. The results presented in this paper were produced between 2013 and 2016 and planned to
explore several dimensions of this methane production plan. These works aimed at produce knowledges about biogas plant resources management and about digestate. Such knowledges and tools should be used to support biogas plant managers and territory stakeholders in order to analyze their own model from an agronomic and environmental point of view. Based on field experience cases, brakes and levers of such projects development have been gathered in a methodology guide. Upstream and downstream biomass and fertilizers flux have equally been explored in order to establish an analysis frame of resources management per biogas plant.
Additional works have been conducted about digestate. Several digestates features were studied.
Nitrogen fertilizing value of 5 digestate types were determined, and evidenced a great variability of
digestates quality regarding this topic. Ammonia remains the major part of total nitrogen (>70%).
Phosphorus bioavailability is 100%, as revealed by isotopic tracing. Biochemical fractioning and Carbon
and Nitrogen potential mineralization showed variability of amending digestates properties (ISMO
73±8%, n=19). Nevertheless, these works remain limited by the number of biogas plants under study
(n=3) and argue for going further into such analyses
Alkalinity and structure of soils determine the truffle production in the Pyrenean Regions
Aim of study: The program "Typology of truffle stations in the Pyrenean Regions" aimed to define the ecological conditions and culture practices that favor Tuber melanosporum growth and fruiting in this area.
Area of study: Navarra, Catalonia, Midi-Pyrénées and Languedoc-Roussillon.
Material and methods: The program was based on the survey of 212 wild and cultivated truffle beds of evergreen oaks (Quercus ilex). The data collected in the field consisted of photographs, samples of soil, roots and mycorrhizae, and information on cultural practices followed by truffle growers.
Main results: (i) truffle soils are alkaline, from neutral, dolomitic, to moderately or very calcareous soils; (ii) truffle soils are light, well-structured and stable to water immersion; (iii) mycelium that colonizes roots survives in suboptimal conditions, but it does not necessarily bear ascocarps. Finally our results suggest that T. melanosporum is a relatively ubiquitous fungus able to grow, or at least to persist, in a wide range of physical and chemical soil conditions. We propose a probabilistic model of the environment favorable for fruiting, built around a two-dimensional graph with an axis for the chemical conditions, like soil alkalinity, and another axis for the physical conditions, like soil structure.
Research highlights: Soil alkalinity and structure allow to built a convenient representation of the ecological capacity of a place to be good T. melanosporum habitat, and thus of the probability for truffle growers to harvest truffles according to the environmental properties of their truffle orchards