Phosphate-Solubilizing Bacteria Cereibacter sphaeroides ST16 and ST26 Enhanced Soil Phosphorus Solubility, Rice Growth, and Grain Yield in Acidic-Contaminated Saline Soil

Soil phosphorus is heavily restricted by soil acidification and salinization. There is a need to determine a biological solution for this issue to replace the overuse of chemical phosphorus fertilizer that aggravates adverse conditions, such as salinity, acidity, and metallic toxicity. Therefore, this study aimed at determining the phosphorus dynamics in terms of the soil, growth, and yield of rice under the supplementation of phosphate (P)-solubilizing purple nonsulfur bacteria (PNSB), <i>Cereibacter sphaeroides</i> ST16 and ST26, in salinized soil collected from An Bien district, Kien Giang province, Vietnam, under greenhouse conditions. The experiment followed a completely randomized block design with two factors and four replications. In particular, the reduced percentages of P fertilizer (A) were 0%, 25%, 50%, 75%, and 100% P. The supplementations of <i>C. sphaeroides</i> strains (B) were the negative control, ST16, ST26, and a mixture of both ST16 and ST26. The results showed that supplying the <i>C. sphaeroides</i> ST16 and ST26 reduced the insoluble P content by 10.1-10.6% Fe-P, 10.3-12.2% Ca-P, and 12.7-43.1% Al-P and increased available P by 8.33-27.8%, leading to total P uptake in plants increasing by 29.4-56.1%. The <i>C. sphaeroides</i> strains also reduced soil Na⁺. Therefore, supplying the <i>C. sphaeroides</i> strains increased the rice growth and yield components of rice, leading to a greater yield of 26.5-51.0%. Supplying each strain of ST16 and ST26 reduced 50-100% P fertilizer as recommended. Ultimately, inoculation of the bacterial mixture allowed a reduction by 100% P fertilizer percentage as recommended but the yield remained the still.