Drip fertigation improves crop nutrient uptake efficiency by precisely regulating fertilizer delivery and altering root spatial distribution. However, its potential to optimize root morphology under phosphorus (P) application-and thereby enhance P uptake, photosynthetic performance, yield, and P use efficiency (PUE)-has not been fully quantified. A field experiment was conducted from 2022 to 2024 in the semi-arid region northeast China to compare drip P fertigation (DPF) with conventional P application (CPA) across five P rates (0, 60, 90, 120, and 150 kg P2O5 ha-1). Soil available P (AP) distribution, maize root morphology, P uptake and utilization, and leaf photosynthetic traits were evaluated. At equivalent P rates, DPF produced a more uniform AP distribution than CPA, significantly promoting root proliferation-particularly in the 20-60 cm soil layer, where root length and root weight increased by 6.5%-16.6% and 4.4%-12.1%, respectively. DPF also improved photosynthetic performance: leaf area index at R6 increased by 3.9%-11.4%, while at R2, net photosynthetic rate, stomatal conductance, and transpiration rate increased 3.8%-9.0%, 3.3%-12.5%, and 1.9%-9.3%, respectively. These physiological enhancements increased grain yield by 2.6%-6.7%. Notably, the high-yielding performing DPF treatment at 90 kg P2O5 ha-1 (P90) surpassed the CPA treatment at 120 kg P2O5 ha-1 (P120), enhancing P uptake and P recovery efficiency (REP) by 3.2% and 10.1 %age points, respectively. Regression analysis indicated that the optimal P rate for balancing yield and PUE was 80-89 kg ha-1 for DPF, compared with 108-120 kg ha-1 under CPA. Consequently, DPF can increase maize yield by 2.7%, reduce P fertilizer input by 25.9%, and improve REP by 10.0 %age points relative to CPA. DPF enhances root growth by optimizing soil spatial distribution, thereby strengthening plant P acquisition and photosynthetic capacity, and ultimately achieving synergistic improvements in maize yield and PUE.