Two greenhouse experiments were carried out during 2019/2020 and 2020/2021 seasons at the Experimental Farm of the Agronomy Department, Faculty of Agriculture, Al-Azhar University, Nasr City, Cairo, Egypt. These experiments aimed to investigate the effect of nine phosphorus (P) and potassium (K) fertilizer rates, i.e., F₁(unfertilized-control), F₂(100 kg P), F₃(200 kg K), F₄(50 kg K), F₅(100 kg P + 50 kg K), F₆(200 kg P + 50 kg K), F₇(100 kg K), F₈(100 kg P + 100 kg K) and F₉(200 kg P + 100 kg K) on broad bean plants grown at two irrigation regimes, i.e. Ir₁ (well-irrigation treatment) and Ir₂(drought stress).
The obtained results could be summarized as follows:
    Drought stress treatment significantly decreased plant height, leaf area/ plant, net assimilation rate, number of flowers produced per plant and pod setting as compared with the well irrigation treatment in both seasons. Drought stress treatment significantly decreased number of pods, weight of pods and seed yield per plant as compared with the well-watered treatment in both seasons.Phosphorus and potassium fertilization increased all studied traits as compared with control (unfertilized treatment) in both seasons. There was a significant interaction between phosphorus and potassium fertilization treatments and irrigation regimes. However, the highest seed yield /plant was obtained under the application of F₄ (50 kg K), F₃ (200 kg P) and well irrigation treatment in first season and second season, respectively. Phosphorus and potassium fertilization increased the drought tolerance of broad bean.