Background and purpose <p>Phosphorus (P) influx kinetics of plants, characterized by <i>I</i>_max (maximum uptake rate) and K_m (P concentration where the uptake rate equals half of <i>I</i>_max), serve an important furnction in quantifying P use efficiency. In addition, knowledge of <i>I</i>_max and K_m at various developmental growth stages is used in modelling P uptake. The objective of this study was to evaluate if and how <i>I</i>_max and K_m vary across growth stages and between different maize (<i>Zea mays</i>) hybrids.</p> Methods <p>Four corn hybrids, released in 1952, 2008, 2018, and 2023, were grown in a sand-culture hydroponics system to various developmental stages (V4, V7, V12, R1, R3, R4, R5, and R6). After non-destructive harvesting, roots of intact plants were washed free of sand and placed in solution to measure P uptake using the solution nutrient depletion method to determine <i>I</i>_max and K_m.</p> Results <p>Results showed that <i>I</i>_max and K_m (per-plant basis) were similar among corn hybrids but different between growth stages. <i>I</i>_max and K_m values increased until around V12 stage and then remained relatively stable throughout the reproductive stages (R1–R6). When expressed per unit root surface area (RSA), <i>I</i>_max peaked at V4 to V7, declined drastically until V12, and remained relatively stable between R1 and R6. <i>I</i>_max expressed per unit RSA was also similar across hybrids.</p> Conclusion <p>Previous work assumed constant <i>I</i>_max and K_m across growth stages; thus, these findings represent a substantial advancement in understanding P influx kinetics and results can be used to improve P uptake models. Results also demonstrated how P influx was partly dictated by root and shoot P concentration, rather than total biomass.</p>