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• Soil properties influence long-term P transformations in fertospheres. • P pools were examined in-situ using soil solution, isotopic dilution, and XANES. • P precipitation and sorption reactions were ongoing at 12 months. • Potentially-plant available P was controlled by soil type. Identifying the effects of soil properties on the transformations of phosphorus (P) in highly concentrated fertiliser bands is a critical component in improving P fertiliser use efficiency, but little is known regarding the kinetics of P transformation, including over longer periods of time that are relevant to multiple cropping seasons. In the present study, we utilised a 12-month soil-fertiliser incubation experiment to simulate deep-placed banded P fertilisers, investigating three contrasting soils from Australia, three P sources, and the co-application of potassium (K). Overall, concentrations of soil solution P in the fertosphere decreased substantially over time regardless of soil type and P form. In the Ultisol and Vertisol, this progressive decrease was due to the precipitation of aluminium-phosphates (and, to a lesser extent, magnesium-phosphates) as well as ongoing sorption reactions, whilst in the alkaline Alfisol this progressive decrease was due to precipitation of calcium-phosphates. Despite P precipitation and sorption reactions, concentrations of potentially-plant available P measured by isotopically exchangeable P within 24 h (Ee24h) remained relatively constant between 1 and 12 months for the Ultisol and Vertisol, with this indicating that the ongoing sorption reactions of P in these fertospheres of non-calcareous soils may not necessarily decrease plant availability over time. We also found that co-application of K resulted in further reduction in P availability in all three soils and was mediated by K displacement of other exchangeable cations, thereby increasing precipitation reactions with dominant minerals. To improve P use efficiency in semi-arid cropping environments, optimising P form as a function of soil type is critical, especially for systems that are reliant on subsoil moisture and where highly concentrated fertiliser bands are applied infrequently to supply P over multiple growing seasons. [ABSTRACT FROM AUTHOR]