Did67 a écrit :Oui. En effet, tu parles là de la rhizosphère.
Mais on est là dans des échanges "minimalistes" : quelques molécules, etc... C'est plutôt les plantes qi nourrissent des bactéries, via les exsudats. Ce qui est loin d'être anecdoitique. Mais les termes de l'échange,c 'ets plutôt protection nettoyage, signaux chimiques...
Les légumineuses ont une "grosse cavalerie", qui peut leur fournir 50 % de l'azote (on est là dans des centaines de kg / ha), grâce à des Rhizobiums, hébergés dans des nodules - des excroissances de leurs racines.
Justement, comme j'ai déjà essayé de le dire, il semblerait que toutes les plantes soient capables d’alimenter des bactéries fixatrices d'azote. Les légumineuses le font directement via les nodosités dans leurs racines, alors que les autres plantes alimenteraient des bactéries fixatrices libres, via la rhizodéposition ; cette deuxième voie ne fonctionnant que dans un sol riche en carbone et bien agrégé.
All green plants form associations with nitrogen-fixing bacteria. This phenomenon is not restricted to legumes.
The atmosphere is around 78% nitrogen, which equates to roughly 78,000 tonnes of dinitrogen gas above every hectare of land. The key to productive and profitable farming is to create – through the establishment of biodiverse pastures and use of biology-friendly fertilisers – a soil environment that supports the presence of free-living and associative nitrogen-fixing soil microbes.
Chlorophyll is part of a protein complex that contains nitrogen, hence wherever you see green plants (any kind of green plant, not just legumes), some form of microbial nitrogen fixation is taking place.
The reason most nitrogen-fixing microbes have gone unrecognised is that they are not able to be cultured in the laboratory. However, recent bio-molecular methods for determining the presence of the nif genes that code for nitrogenase reductase have revealed a dizzying array of free-living and associative nitrogen-fixing bacteria and archaea in a wide range of soils associated with every kind of crop and pasture plant, including grasses and non-legume herbs.
In well-functioning soils, 85-90% of plant nutrient uptake is microbially mediated and N is no exception. The first-formed product of biological nitrogen fixation, NH3, is rapidly converted (within milliseconds) to non-toxic NH4+, which in turn is rapidly transformed to amino acids.
Amino forms of N are the most metabolically efficient for plant uptake. Further, in a closed N cycle, nitrogen cannot leach to waterways, volatilise to the atmosphere, or form toxic nitrates that poison stock (and people). Additionally, the storage of nitrogen in the organic form reduces the likelihood of soil acidification.
Unfortunately, many biological functions, including natural nitrogen fixation, are compromised by commonly used agricultural practices. The application of high-analysis inorganic N, for example, inhibits both associative diazotrophs and mycorrhizal fungi, the key intermediaries in the fixation and transport of organic N. The ultimate irony for farmers is that the application of high rates of inorganic N inhibit the microbial communities that are able to fix atmospheric N for free, making production even more dependent on N inputs. Once soils become ‘addicted’ it is hard to kick the nitrogen habit.
https://pureadvantage.org/news/2017/05/ ... al-limits/
