Phosphate-Solubilizing Rhizosphere Bacteria Enhancing Phosphorus Uptake and Maize Yield in Dyked Alluvial Soil

Low phosphorus (P) availability, despite adequate total P, is a major constraint to maize production in dyked alluvial soils (DAS) of the Mekong Delta, Vietnam. Conventional P fertilizers are inefficient in these soils, leading to low P use efficiency and reduced yield. Thus, the aim of this study was to identify phosphate-solubilizing rhizosphere bacteria (PSRB) from maize cultivation soil and assess the performance of selected indigenous bacteria in maize cultivation in DAS.

A total of 36 maize rhizosphere samples from DAS were collected to isolate PSRB and determine which was most beneficial for maize cultivation. Additionally, the pot experiment consisted of nine groups as follows: 100% phosphate according to the recommended fertilizer formula (P-RFF), 75% P-RFF, 50% P-RFF, 25% P-RFF, 75% P-RFF and PSRB, 50% P-RFF and PSRB, 25% P-RFF and PSRB, 0% P-RFF and PSRB, and 0% P-RFF in DAS with low phosphorus availability.

The results indicated that among the 67 isolates, strains ASD-15, ASD-43, and ASD-56 exhibited the highest phosphorus concentrations, solubilizing 74.1 mg Al-P/L, 42.2 mg Ca-P/L, and 98.0 mg Fe-P/L, respectively, after five days of incubation. The strains were identified as Enterobacter asburiae by 16S rDNA sequencing. The application of PSRB increased soil-soluble P by 7.1 mg kg⁻¹ compared with the uninoculated control, enhanced total P uptake in maize by 31%, and improved grain yield by 20.2%. Notably, combining PSRB with 75% P-RFF achieved yield and P uptake equivalent to 100% P-RFF, indicating that biofertilizer use could reduce chemical P fertilizer input by 25% without yield reduction.

Indigenous PSRB, E. asburiae, can improve soil P availability and maize productivity in DAS, supporting reduced reliance on chemical fertilizers. Future work should validate these findings under field conditions and explore PSRB-based biofertilizer formulations for large-scale application.