Root-induced processes controlling phosphate availability in soils with contrasted P-fertilized treatments
Devau, Nicolas | Hinsinger, Philippe | Le Cadre, Edith | Gérard, Frédéric
AIMS: In this study we identified the nature of the root-induced chemical processes controlling changes in phosphate (P) availability in a soil with two P loadings resulting from long-term fertilization treatments. METHODS: We used a set of mechanistic adsorption models (surface complexation and ion exchange) within the framework of the component additive approach to simulate the effect of durum wheat roots on P availability. We had to consider the influence of adsorption of other ions to ensure the goodness-of-fit of the simulations. RESULTS: We found that Ca²⁺ uptake, in addition to P uptake and root-induced alkalization, controlled P availability in the rhizosphere regardless of the fertilization level. The relative influence of these three processes depends primarily on the extractant used to estimate P availability. Calcium uptake was the most significant process in water extracts, whereas P uptake was the dominant root-induced chemical process in CaCl₂ extracts. Under low Ca concentrations, Ca²⁺ uptake decreased the promoting influence of Ca²⁺ adsorption on P adsorption. CONCLUSIONS: In addition to confirming the validity of our approach to model P availability, the present investigation indicated that root-induced processes markedly affect P availability irrespective of the fertilization level.
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