| Abstract: From 2024 to 2025, a fixed-site field experiment was conducted in the apple production area of the Weibei region on Loess Plateau, Shaanxi Province. Full-bearing ‘Red Fuji’ apple trees were used as the test material, and six treatments were established, including no phosphorus (P) fertilizer input (CK) treatment and P input treatments of diammonium phosphate with a phosphorus activator (Act-P), polyglutamic acid diammonium phosphate (PGA), ammonium polyphosphate (APP), alginate oligosaccharide diammonium phosphate (ADO-P1), and conventional diammonium phosphate (DAP). The effects of different phosphate fertilizers on apple tree nutrition, yield components, fruit quality, and soil nutrient content were systematically compared, with the aim of screening high-efficiency phosphate fertilizer types suitable for the calcareous soil in Weibei dryland. The results showed that the new-type phosphate fertilizers were generally superior to conventional diammonium phosphate (DAP) in activating soil phosphorus, improving tree nutrient status, and increasing both yield and fruit quality. Compared with the DAP treatment, the Act-P and PGA treatments significantly increased soil available phosphorus content in the 0–40 cm soil layer, while the APP and DAP treatments were beneficial for maintaining soil nitrate nitrogen and ammonium nitrogen levels; The Act-P, PGA, and APP treatments increased nitrogen, phosphorus, and potassium contents to varying degrees in both new and old apple leaves from the fruit setting stage to the maturity stage. Among them, PGA and ADO-P1 exhibited particularly pronounced improvements in leaf nutrients during the fruit setting and fruit enlargement stages. In terms of yield performance, the PGA treatment ranked first in single fruit weight and yield per hectare for two consecutive years, followed by APP and Act-P. Compared with DAP, the average yield per hectare of PGA and APP increased by 28.0% and 17.5%, respectively, and their phosphorus partial factor productivity was also significantly higher than that of DAP. Regarding fruit quality, the PGA treatment was most effective in enhancing soluble solids content, soluble sugar content, and the sugar-acid ratio, followed by the Act-P and APP treatments. Furthermore, all new-type phosphate fertilizer treatments effectively reduced titratable acid content and increased vitamin C content compared with DAP. In conclusion, polyglutamic acid diammonium phosphate and ammonium polyphosphate demonstrated strong phosphorus activation capacity and prolonged phosphorus supply duration under the calcareous soil conditions of Weibei region. They can synergistically improve apple leaf nutrient status, yield, and fruit quality while maintaining soil nitrogen nutrition. As more efficient new phosphate fertilizer types compared with traditional diammonium phosphate, they hold great application potential for precise phosphorus fertilization and phosphorus fertilizer upgrading in apple production in this region. |