Objective  A fungal strain highly efficient in dissociating low-grade phosphorus ore for fertilization was isolated to determine the applicability.

  Method  Soil samples at Guizhou Tongren Tobacco Planting Base were screened using the sand culture method for fungi that exhibited capability to solubilize phosphate. The selected isolate was identified by physiological, biochemical, and molecular biological tests. Conditions for optimal phosphate solubilization were determined by single factor and orthogonal experiments. Effect of the fungal addition on fertilization was verified by a pot test conducted on tobacco seedlings.

  Result  The selected isolate was code-named JL-7 and, subsequently, identified to be a strain of Aspergillus fumigatiaffinis. The optimized conditions to maximize the phosphate-solubilization of JL-7 applied an inoculation at the rate of 1×10⁵ cfu·mL⁻¹ with an initial pH of 6 to incubate at 26 ℃ for 8 d. The process dissolved a low-grade phosphorus ore material up to 967.4 mg·kg⁻¹ with the resulting solution reduced to approximately pH 2.9. In the pot experiment, the Yunyan 87 tobacco seedlings grown on a medium with the addition of a JL-7-inoculated phosphorus fertilizer had the stem girth, plant height, and maximum leaf area increased by 44.60%, 57.29%, and 62.90%, respectively, over control. Meanwhile, the pot soil increased 48.5% on available phosphorus, 3.7% on available potassium, and 9.1% on alkali-hydrolysable nitrogen after the planting as well.

  Conclusion  The identified strongly phosphate-solubilizing Fungus JL-7 displayed a significant and consistent ability of dissolving phosphate. It was considered a potential candidate to be widely promoted as a microbial fertilization enhancer.