Large-scale mineral exploitation causes heavy metal pollution and nutrient depletion in mining-area soils, making heavy metal control and soil fertility improvement urgent. This study synthesized biological magnesium ammonium phosphate (bio-MAP) via microbially induced mineralization, characterized its microstructure, and conducted pot experiments with ryegrass and alfalfa under different bio-MAP additions to analyze effects on soil physicochemical properties, Pb²⁺/Cd²⁺ contents, and plant growth. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) confirmed the precipitate was mainly struvite (MgNH₄PO₄·6H₂O) with a regular orthorhombic structure. Appropriate bio-MAP addition not only facilitated the formation of large soil aggregates and enhanced soil structural stability but also significantly promoted the growth of ryegrass and alfalfa. At the 30-day harvest, the total fresh weight of ryegrass reached 1.33 g in the P5 treatment (bio-MAP addition: 1000 mg/kg), while that of alfalfa reached 2.36 g in the P3 treatment (bio-MAP addition: 500 mg/kg). Compared with the control, the P1, P3, and P5 treatments reduced soil available Pb content by 7.16 %, 15.1 %, and 19.28 %, respectively, and soil available Cd content by 58.57 %, 62.31 %, and 65.1 %, respectively. Bio-MAP also increased soil sucrase activity and abundances of Proteobacteria, Actinobacteria, and Bacillus. This study provides a new method for mine soil amendment and heavy metal control, plus references for ecological restoration.
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