Accelerated phosphorus immobilization at high soil temperatures may decrease net mineralization

Soil phosphorus (P) mineralization (P min ) is expected to be sensitive to temperature, but the degree of temperature sensitivity remains uncharacterized. We quantified the temperature sensitivity of gross P min , P immobilization (P imm ) and resulting net P min at 5°, 10°, and 20° C using 33 P-labeling and isotopic exchange kinetics in soils (0-15 cm depth) of varying biophysical properties from four sites with long-term agricultural management practices (30-145 y) and one restored prairie (34 y) encompassing a 350 km latitudinal transect representative of the central USA. Over 28 d, gross P min and P imm fluxes were consistently higher than 5° and 10° C, resulting in 3.7-fold larger gross P min versus P imm pools at 20° C and 5- to 37-fold larger than gross P min and P imm at lower temperatures. Cumulative net P min pools plateaued by 3-7 d at 5° and 10° C but increased over 28 d at 20° C, though net P min pools more closely approximated temporal changes in gross P min pools at 5° and 10° C compared to at 20° C (i.e., low P min efficiency). Multivariate least absolute shrinkage and selection operator (LASSO) models indicated gross and net P min at 10° C were most strongly predicted by silt plus clay content (S+C), followed by microbial biomass C, soil phosphatases that catalyze gross P min (PME) and organic C-to-P ratios (C:P o ), P imm at 5° C by S+C and microbial biomass nitrogen, and all pools at 20° C by P o and microbial biomass C. Notably, PME activities were important predictors of P imm at 20° C but not gross not net P min at the same temperature, and P imm at 10° C and both P min pools at 5°C were best predicted by univariate relationships with C:P o and pH, respectively. Our study identifies the capacity for soil temperature to modulate which and how biophysical soil properties influence soil P mineralization-immobilization, likely due to shifts in sorption-desorption equilibria that enhance microbial P uptake, potentially leading to lower net P min contributions to crop uptake.