Integrated phosphorus management strategy improves maize phosphorus use efficiency by coordinating root-zone phosphorus availability and root architecture under reduced-P drip irrigation

<title>Abstract</title> <p> <italic>Background and aims</italic> In calcareous soils, Ca ²⁺ -mediated P fixation and surface P accumulation limit the spatial matching between P supply and roots, reducing maize P uptake and PUE. This study evaluated whether integrated P management combining banded deep P placement with γ-polyglutamic acid (γ-PGA) could sustain maize yield and improve PUE under reduced P input. <italic>Methods</italic> A two-year field experiment was conducted in 2024-2025 with two maize cultivars and five P treatments: no P (P0), conventional P (P1), 20% reduced P (P2), 20% reduced P plus γ-PGA (P3), and 20% reduced P plus γ-PGA with deep P placement (P4). <italic>Results</italic> Compared with P1, P2 reduced yield by 7.6%-21.5% and significantly decreased plant P accumulation and PUE. P3 maintained yield and partly alleviated reductions in P accumulation and root growth. P4 maintained yield, increased PUE by 15.6%-27.1%, reduced apparent P balance by 51.3%-64.8%, and increased the Post-anthesis P contribution to grain by 8.5%-15.2%. P4 increased root length, root volume, and crossings, promoted very fine root proliferation and deeper root distribution, and improved root fractal characteristics. In the 30-40 cm soil layer, Resin-P, NaHCO₃-Po, and available P increased by 26.8%, 20.8%, and 31.2%-38.5%, respectively. PLS-PM indicated that active P fractions were closely associated with root architectural optimization and plant P accumulation. <italic>Conclusion</italic> Integrated P management effectively reconstructed root-soil spatial coupling, enabling high yield and efficient P utilization under reduced P input in drip-irrigated calcareous soils. </p>