Soil beneficial bacteria: Harnessing tools for optimizing citrus growth and soil health in pH-stressed soils.

Abstract

Rhizosphere bacteria can support crop production by promoting plant health, soil fertility, and resilience to biotic and abiotic stresses. However, the potential role of soil-beneficial bacteria, particularly plant growth-promoting rhizobacteria (PGPR), remains inadequately explored in citrus production grown on pH-stressed soil. This study aimed to evaluate the effect of PGPR on citrus growth and soil health indicators under pH-stressed Florida sandy soil. A greenhouse study was conducted at the University of Florida, Lake Alfred, which followed a 3 × 3 factorial randomized complete block design with three soil pH levels (5.0, 6.5, and 8.0) and three PGPR (P)/fertilizer (F) combinations (P + 75% F, P + 100% F, and 100% F only). Soil pH conditions were adjusted using a soil neutralization curve generated by soil incubation methods. The results showed that the soil pH factor significantly influenced most crop growth parameters, with optimal results at a pH of 6.5. PGPR significantly (p < 0.05) improved the plant height (27.84 cm), root mass density (7.65 mg/cm³), stem diameter (4.89 mm), and aboveground biomass (2.64 g/ plant) compared to without PGPR application. No significant difference between 75% and 100% fertilizer rates were found in crop and soil attributes when PGPR was applied. Soil organic matter and microbial respiration were also significantly improved (p < 0.05) with PGPR inoculation by 1.15 and 1.65 folds, respectively, compared to 100% F-only treatment. The availability of soil nutrients was influenced by PGPR treatments, which likely enhanced nutrient uptake and improved crop growth even with a reduced fertilizer rate. The results suggested that PGPR inoculation combined with partial fertilization can improve soil health indicators and plant growth, even in pH-stressed sandy soils.