Acinetobacter Radioresistens Ke–5 Oxidises Elemental Sulphur in Sodic Soil and Affects Crop Performance

Native sulphur–oxidizing communities are essential for the success of elemental sulfur (S⁰)–based sodicity reclamation. This study reports the sulfur–oxidizing capacity of Acinetobacter radioresistens Ke–5 evaluated under laboratory incubation and lysimeter conditions with soil of varied sodicity (9.8–10.9 pH and exchangeable sodium percentage 62.5–98.2%) collected from different agro-ecologies. Inoculation response was evaluated in a rice-wheat cropping system under lysimeter conditions, with treatments allocated following a randomized block design with five replications. The strain exhibited multiple beneficial traits, including producing titratable acidity, secreting ammonia and indole–3–acetic acid (IAA), and solubilizing phosphorus and zinc. The strain Ke–5 formed biofilms around sulphur particles. PCR analysis confirmed the presence of soxA , soxB , and soxY genes associated with the Sox cluster gene for S oxidation. Inoculation of sodic soils (pH 9.1–10.5) with A. radioresistens strain Ke–5 significantly enhanced S⁰ oxidation ranging from 3.7% to 29.4%. Enhanced S 0 oxidation was associated with reduced bicarbonate concentration and total soil alkalinity, along with increased Ca 2+ and Mg²⁺ concentrations in the soil solution. The increased Ca 2+ and Mg 2+ reduced the sodium adsorption ratio by 32–41% and potentially facilitated Na⁺ displacement from soil exchange sites. The combined application of the strain Ke–5 with S⁰ caused a 4.8–19.3% increase in rice and wheat yield compared to the application of S⁰ alone. These results suggest that A. radioresistens Ke–5, with S 0 –oxidation and plant growth-promotion capabilities, can be a promising option for improving the efficiency of S⁰ -based reclamation and plant growth promotion in sodicity-affected soils. However, field validation and more comprehensive genomic and phenotypic safety assessments are required before adoption as a bioinoculant.