Effects of phosphate-solubilizing bacteria in the rhizosphere of Camellia oleifera on phosphorus fractions and phosphorus transformation in red soil with different textures

Abstract:

Objective Phosphate-solubilizing bacteria (PSB) can increase available phosphorus by promoting the transformation of different phosphorus forms in soil. However, the phosphate-solubilizing ability of PSB is influenced by soil texture. Therefore, we studied the changes of phosphorus fractions in red soil with different textures and treated with PSB, with the aims of improving the efficient utilization of soil phosphorus.Methods We collected the rhizosphere soil samples of four main Camellia oleifera varieties (‘Huashuo’ ‘Huaxin’ ‘Huajin’ and ‘Changlin No. 40’) in Liuyang City, Hunan Province. PSB strains were isolated, purified, screened, and identified by plate coating, transparent circle method, molybdenum-antimony anti-spectrophotometric method, and 16S rRNA gene sequencing, and a batch of highly efficient PSB strains were obtained. The phosphate-solubilizing abilities of the obtained PSB strains were investigated with different phosphorus sources (iron phosphate, aluminum phosphate, calcium phosphate, and calcium phytate). PSB were inoculated into the red soil samples added with 0, 20% and 40% perlite (0%PR, 20%PR and 40PR%) to clarify the changes in phosphorus fractions in the red soil samples with different textures.Results A total of 57 strains of PSB were isolated from the rhizosphere of C. oleifera, of which strains CL37, HS5, and CL36 exhibited stronger phosphate-solubilizing abilities. The three strains were identified by 16S rRNA gene sequencing and named Pantoea sp. CL37, Burkholderia sp. HS5, and Burkholderia sp. CL36, respectively. The three strains showed significant differences in their ability to solubilize different phosphorus sources, with the highest solubilizing ability for calcium phytate and calcium phosphate. Compared with CK, the inoculation of PSB increased the available phosphorus (AP) in soil by 8.90%-54.60% and 1.90%-56.00% in 20%PR and 40%PR, respectively. The inoculation with PSB increased Fe-P, Resin-P, NaHCO₃-Pi, and NaOH-Pi, which showed a tendency of first increasing and then decreasing along with the increase in the addition of perlite in red soil. Meanwhile, PSB decreased the content of HCl-Pi and Residual-P, and the decrease in HCl-Pi was more pronounced in 20%PR than in 0%PR and 40%PR. Of all treatments, the inoculation with HS5 led to the highest increases in Fe-P, Resin-P, NaHCO₃-Pi, and NaOH-Pi in the soil samples analyzed. Correlation analysis and random forest analysis suggested that AP was mainly affected by Resin-P, Al-P, NaOH-Pi, acid phosphatase, urease, pH, and NaOH-Po.Conclusion The phosphate-solubilizing pathways of PSB vary in red soil with different textures. Strain HS5 has a strong phosphorus-transforming ability and is more conducive to phosphorus transformation in the red soil with 20%PR.