Scheduling irrigation play avital role to rationalize irrigation water in arid and semi-arid regions. A field experiment was conducted at Sakha Agricultural Research Station, Kafr El-Sheikh, Egypt in 2019 and 2020 to study the effect of irrigation scheduling; Irrigation was applied at 1.2, 1.0 and 0.8 of accumulative pan evaporation (APE) and potassium foliar spray 0 (F₁), 1.0 (F₂), 2.0(F₃) and 3.0 (F₄) gL^-1 K₂O on growth, physiology, yield and water productivity of maize. Results demonstrated that water consumptive use and applied water at 1.0 of APE and 0.8 of APE were decreased by 6.7% and 6.0%; 14.8% and 16.6%, respectively in comparison with to 1.2 of APE as an average of both seasons. The best growth, physiology, yield, and yield component were achieved when maize plants irrigated at 1.2 of APE, whereas the highest values of water productivity were achieved when plants irrigated at 1.2 of APE and 1.0 of APE treatments without any significant differences between them. Plant hight, leaf area, total chlorophyll, proline concentration, leaf transpiration, stomatal resistance, shelling percentage, 100 kernel weight, biological and grain yield, water consumptive use and water productivity took the descending arrange F₄> F₃> F₂> F₁. Under study condition, it could be concluded that the application of irrigation at 1.0 of APE×F₄interaction, achieved a reasonable grain yield, saved irrigation water, and enhanced water productivity in comparison with all studied treatments as well as, irrigation at 1.2 APE × F₄ interaction.