Phosphorus mobilization and acquisition in the alkaline-calcareous rhizosphere: A synthesis

Phosphorus is an essential macro-nutrient that often limits plant productivity in agricultural soils, particularly in alkaline-calcareous soils. In these soils, phosphorus availability is primarily controlled by sorption and precipitation reactions. This paper critically reviews and synthesizes the principal strategies through which rhizosphere processes modulate phosphorus bioavailability in such typical soils, providing a valuable resource for researchers and practitioners on the current state of knowledge. The review also emphasizes the importance of rhizosphere processes and their applications in developing sustainable farming practices. It focuses on recent advancements in root exudation, anatomical and molecular mechanisms, and their interactions with key agricultural practices. Furthermore, it synthesizes and discusses cutting-edge rhizosphere research, pinpointing opportunities for future explorations. Several knowledge gaps were identified. For instance, there is a paucity of information regarding the trade-offs between root morphological and physiological traits (e.g., root exudates) in response to phosphorus deficiency. Additionally, metabolomics needs to be integrated to unravel the molecular mechanisms involved in rhizosphere interactions. Further research is also required to identify specific plant and microbial traits that contribute to rhizosphere acidification in calcareous soils.