Role of Soil Minerals on Organic Phosphorus Availability and Phosphorus Uptake by Plants

Abstract AimsOrganic P (OP) accounts for significant fractions of the total phosphorus (P) pool in soils, especially in soils treated with organic inputs. In soils, OP compounds can be sorbed onto soil minerals but the consequences of these interactions on P availability and plant uptake are poorly known. This research aims at elucidating the extent to which adsorbed OP compounds to major soil minerals may be available to plants.MethodsRyegrass (Lolium multiflorum) plants were grown in RHIZOtest devices in the presence of OP (myo-inositol hexakisphosphate (IHP), glycerophosphate (GLY) and glucose-6-phosphate(G6P)) and inorganic P (IP) compounds that were previously adsorbed onto Fe and Al oxides (goethite and gibbsite, respectively) and clay minerals (montmorillonite and kaolinite). Phosphorus availability and P uptake were then determined through rhizosphere and plant characterization. ResultsIrrespective of the type of mineral, ryegrass was able to take up about 3-18% of adsorbed OP compounds. The magnitude of availability and uptake depended on the OP compounds and the type of soil minerals. The potential availability of OP adsorbed by different minerals was strongly mediated by mineral-OP interaction types and properties. The P uptake increased in the following order: kaolinite-OP << gibbsite-OP ≤ goethite OP << montmorillonite-OP. Phosphorus uptake from adsorbed OP compounds showed contrasting pattern compared to adsorbed IP and depended on available P in the rhizosphere and not necessarily on the binding strength of OPs to the mineral surface.ConclusionsUnravelling the role of both OP and soil minerals properties on P availability constitutes an important knowledge to understand P dynamic in soil-plant system. Our results evidenced that the forms of OP adsorbed on Fe and Al oxides or clay minerals are available for plants to an extent which is strongly driven by OP forms and mineral types.