Background and Aims: Bioavailable phosphorus (P) represents a primary constraint on productivity in many ecosystems on highly-weathered soils. Soil moisture can be important to determining P bioavailability and net primary productivity in these systems. However, hydrologic controls on P availability remain poorly understood. Methods: We used resins (anion-exchange membranes) to quantify the response of liable P, an estimate of bioavailable P, to soil moisture conditions in two highly weathered soils (rendzina, ultison). The resins were either incubated in soil or shaken with a soil water slurry. Results: Resin incubations in aerobic soil effectively quantified P in soils under changing moisture conditions, extracting significant amounts of labile P while avoiding the disturbance impossed by slurries. Wetting field-moist soils resulted in pulsed labile P, with lagged peaks occurring days after the largest moisture additions. Re-wetting air-dried soils enhanced labile P immediately, with the largest amounts observed at the highest moisture levels; labile P steadily declined following the moisture addition. Conclusion: Soil moisture levels and history strongly impacted labile P, indicating the importance of both variables when interpreting labile P measurements. These results also suggest that P availability is linked to both the amount and timing of rainfall, with implications for plant productivity in regions exposed to changing moisture regimes.