Phosphorus limitation enhances root exudation and mineral bioweathering across diverse soil process domains

Aims: Harnessing rhizosphere processes offers a valuable opportunity to optimize nutrient use efficiency in agroecosystems. In nutrient-limited soils, plants discharge part of photosynthate surplus via root exudation, including carboxylates, which may enhance mineral dissolution and nutrient mobilization. We aimed to assess how plant responses to nutrient limitation translated into changes in exudate profiles, and how these exudates, in turn, drive bioweathering across soils of contrasting mineralogy and weathering degree. Methods: We conducted a hydroponic experiment with Lupinus albus grown in a phosphorus (P) gradient over seven weeks. We measured plant biomass and root traits, performed a metabolomics analysis and quantified seven carboxylates in root exudates using gas chromatography-mass spectrometry. To assess bioweathering across contrasted soil domains, we conducted batch dissolution tests with exudates using three soil horizons-each with distinct physicochemical properties: enriched in organic matter, iron oxides, or primary silicates. Results: At the intermediate level of P supply, shoot biomass was comparable to that under high P, but plants produced more root biomass and a higher total carboxylate exudation rate. Despite low carboxylate concentrations (