Nutrient management was examined by cultivating leguminous crops to explore how fertilizer applications influence the availability of phosphorus (P) and potassium (K). A greenhouse experiment was directed with chickpea and pea under different fertilization applications. The treatments were: T0 (control, no fertilizer), T1 (90 kg P ha–1), T2 (90 kg K ha–1), and T3 (combined application of 90 kg P ha–1 and 90 kg K ha–1). Chemical fertilizer applications significantly (p < 0.05) enhanced nutrient uptake and soil enzyme activity, with the combined treatment (T3) producing the most pronounced effects. Under T3, nitrogen (N) uptake increased by 37.0% in chickpea and by 151.4% in pea compared with the control. Microbial biomass phosphorus (MBP) also rose markedly under T3, showing increases of 95.7% in chickpea and 81.5% in pea. In chickpea, T1 treatment stimulated N-acetyl-β-D-glucosaminidase (NAGase) activity by 52.4%, while T2 enhanced urease (URase) activity by 50.1%. The combined treatment (T3) substantially elevated β-glucosidase (BGase) and phosphatase (Phase) activities by 55.8 and 33.9%, respectively. In pea, enzyme responses were most significant under T3, where BGase, URase, Phase, and NAGase activities rose by 149.7, 111.9, 81.1, and 70.0% over the control. These outcomes demonstrate that simultaneous P and K application (T3) optimizes soil enzyme activity and microbial biomass phosphorus, thereby improving nutrient availability and uptake in both chickpea and pea.