Objectives In calcareous fluvo-aquic soils, strong P fixation and low P mobility severely limit crop P access, a problem that is further aggravated by the low seasonal temperatures encountered during winter wheat cultivation. To overcome this inherent P availability bottleneck, value-added diammonium phosphate has been engineered, and this work systematically disentangles its chemical and microbial regulatory pathways, as well as its performance under low-temperature stress.

Methods A full-factorial soil incubation experiment was established using calcareous fluvo-aquic soil. The three P management treatments of no P (CK), conventional diammonium phosphate (PP), and value-added diammonium phosphate(MP) fully crossed with three temperature levels of 5°C, 15°C, 25°C. Over a 42-day incubation period, soils were sampled for determination of available P, P fractions, pH, and alkaline phosphatase activities at six time points, while 16S rRNA amplicon sequencing was used to profile microbial communities at the key response stage (day 7).

Results 1) At all three tested temperatures, MP consistently outperformed PP: it boosted alkaline phosphatase activity by 11.20%–21.96%, reduced soil pH by 0.12–0.15 units, and increased available P content by 2.61%–3.46%. 2) Labile P pools (water-soluble P and NaHCO₃-extractable inorganic P) rose as temperature increased, but MP maintained a significant advantage over PP in these bioavailable fractions at every temperature. 3) Compared with PP, MP significantly increased microbial α-diversity (ACE and Chao1) by 10.83%–14.85% at 15°C and 25°C, and selectively enriched core P-solubilizing phyla, leading to a distinct, P-cycling-favorable microbial community. 4) Temperature and P fertilizer type exerted a significant interactive effect (P<0.05) on available P, alkaline phosphatase activity, and microbial diversity, with pH acting as a negative driver and alkaline phosphatase as a positive driver of available P dynamics.

Conclusions Unlike conventional diammonium phosphate, value-added diammonium phosphate can break the P fixation barrier in calcareous fluvo-aquic soil through a synergistic combination of chemical (pH lowering) and biological (enzyme stimulation, P-cycling microbiome optimization) mechanisms, thereby increasing labile P supply. Critically, it retains high P availability even under the low temperatures of 5°C and 15°C, making it a highly promising fertilizer solution for winter wheat production across the North China Plain.