Carbon and nutrient colimitations control the microbial response to fresh organic carbon inputs in soil at different depths

Siegwart Lorène, Piton Gabin, Jourdan Christophe, Piel Clément, Sauze Joana, Sugihara Soh, Bertrand Isabelle. 2023. Carbon and nutrient colimitations control the microbial response to fresh organic carbon inputs in soil at different depths. Geoderma, 440:116729, 11 p.

https://doi.org/10.1016/j.geoderma.2023.116729

Article de revue ; Article de recherche ; Article de revue à facteur d'impact

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Résumé : Despite the potential of subsoil carbon (C) to buffer or amplify climate change impacts, how fresh C and nutrients interact to control microorganismal effects on the C balance in deep soil horizons has yet to be determined. In this study, we aimed to estimate the impact of fresh C input at different soil depths on soil microbial activity. To conduct this study, Mediterranean soils from 3 layers (0–20, 20–50 and 50–100 cm of depth) were incubated over 28 days. Carbon and nutrient fluxes were measured after the addition of an amount of C equivalent to the postharvest root litter derived-C of a barley crop (4.3 atom% 13C), with and without nitrogen and phosphorus supply. We found that the microbial mineralization was C limited in the topsoil, while C and N colimited in the subsoil. These variations in stoichiometric constraints along the soil profile induced different microbial responses to C and/or nutrient addition. A stronger priming effect was observed in the topsoil than in the subsoil, and the sole C addition induced a negative C balance. Conversely, subsoil showed a positive C balance following fresh C addition, changing to critical soil C losses when nutrients were supplied with C. Our results show that fresh C input to subsoil (e.g., through deep-rooting crops) might foster soil C sequestration, but this positive effect can be reversed if such C inputs are combined with high nutrient availability (e.g., through fertilization), alleviating microbial limitation at depth.

Mots-clés Agrovoc : matière organique du sol, substance nutritive, chimie du sol, teneur en éléments minéraux, fertilité du sol, carbone

Mots-clés géographiques Agrovoc : France

Mots-clés libres : Microbial activity, Priming effect, Subsoil, 13C glucose

Classification Agris : P33 - Chimie et physique du sol
P34 - Biologie du sol

Champ stratégique Cirad : CTS 2 (2019-) - Transitions agroécologiques

Agences de financement hors UE : Total Foundation, Agropolis Fondation, Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement

Projets sur financement : (FRA) DSCATT

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