Phosphorus and Potassium Mobilization from Rock-Derived Mineral Sources Using Bacteria and Microalgae: A Review

Basalt rock powder (BRP) has been evaluated as an alternative to soluble fertilizers owing to its phosphorus (P) and potassium (K) content, although their association with low-solubility minerals may restrict availability to plants. This review synthesized evidence on microbial P and K mobilization from rock-derived minerals and examined its relevance to BRP. Scopus and Web of Science were searched for English-language publications through 2025. After merging and duplicate removal, 98 records were sequentially screened, and 33 experimental studies were included. Bacterial evidence predominated, mainly from phosphate rock, hydroxyapatite, tricalcium phosphate, feldspar, and other non-basalt substrates. Studies involving photosynthetic microorganisms covered fewer strains and mineral sources. Direct basalt evidence was limited to K-release measurements from crystalline basalt by cyanobacteria and did not represent mobilization from BRP under soil conditions. Differences in mineral composition and loading, cultivation conditions, incubation periods, analytical fractions, and calculation bases limited direct comparisons. Mineral-P mobilization was associated with acidification, organic acids, and ligand-cation interactions, whereas phosphatase activity represented organic-P mineralization. K-related evidence included acidification, ion exchange, surface alteration, and feldspar-binding proteins. Mixed phototrophic-bacterial systems were evaluated mainly through metabolic interactions or soil and plant responses. Direct comparisons with monocultures were uncommon, and no included study quantified P or K release from BRP by a defined microalgae-bacteria consortium. Further research could clarify the applicability of microbial mobilization to BRP by linking its mineralogical characterization and controlled nutrient-release measurements with formulation stability and responses under soil and field conditions.