Banded application of single superphosphate and ammonium sulfate enhances phosphorus-use efficiency and maize productivity on the Loess Plateau of China

Phosphorus (P) over-fertilization in rainfed maize systems of the Loess Plateau of China contributes to environmental pollution and low P use efficiency. This study assessed how the reduced P fertilization rates and different application methods influence maize yield, P use efficiency, root morphology, rhizosphere enzyme activity, and soil P fractions. Exp. 1 compared a P-unfertilized control (CK), a farmer’s practice (FP) at 52.4 kg P ha −1 , and a reduced rate of 30.6 kg P ha −1 (RF) over four years. Exp. 2 included P-unfertilized control, broadcasted application of single superphosphate (RF), banded application of single superphosphate (BP), and banded application of single superphosphate plus ammonium sulfate (AS) over two years. Maize yield, P use efficiency, root morphology, rhizosphere enzyme activity, and soil P fractions were measured and analyzed. In Exp. 1, reducing P fertilization to 30.6 kg ha −1 (RF) maintained yield, grain P content, and aboveground P uptake compared to the farmer’s practice (FP). In Exp. 2, compared to broadcasted application of single superphosphate (RF), yield was significantly increased by banded application of single superphosphate (BP) and banded application of superphosphate plus ammonium sulfate (AS), with AS showing a 13 % increase over two years. The AS treatment also lowered rhizosphere pH, enhanced labile P pool, and improved root morphology, promoting P uptake. Root traits (total root length, volume, surface area, and average root diameter) at the V3, V10, and R1 stages were positively correlated with the β-1,4-N-acetylglucosaminidase activity, phosphatase activity, and NH 4 + -N availability. Both random forest and Mantel analyses identified soil available P as the primary determinant of yield and P uptake. PLS-PM further revealed that the AS treatment enhanced yield chiefly via its effects on soil available P, enzyme activity, and root traits. Our results demonstrate that a tailored, low-input P management strategy, involving a 42 % reduction in P fertilization combined with banded application of superphosphate and ammonium sulfate enhances yield, improves P use efficiency, and optimizes soil conditions under maize dryland farming. • Reducing P input by 42 % maintained yield and improved P use efficiency. • Banded P fertilizer with ammonium sulfate (AS) promoted yield and P use efficiency. • The AS treatment improved maize root morphology across growth stages. • The AS treatment lowered pH and increased the labile soil P pool. • The strategy supports sustainable P management in dryland maize systems.