Occurrence of Sphingomonas olei with elemental S oxidation capability in sodic soil: Potential role in sodicity reclamation and plant growth promotion

The success of the sodic soil reclamation using elemental S (S°) depends on the population of the native S° oxidizers. Augmenting the native flora of the sodic soils with effective S° oxidizers can enhance the success of the sodic soil reclamation. Present study reports for the first time the S° oxidation potential of the Sphingomonas olei strain 20UP7 isolated from sodic soils with pHs 9.8 and ECe 3.6 dS m–1. Inoculation with S. olei strain 20UP7 caused 13.0–24.2 % increase in S° oxidation in different sodic soils (pHs 9.1–10.5). It improved the concentration of the Ca2+, Mg2+, PO43– and declined the HCO3– and total alkalinity of the soil solution. This isolate also showed appreciable P and Zn solubilization, indole acetic acid, ammonia, and titratable acidity production in the growth media. It tended to the formation of biofilm around sulphur particles. The PCR amplification with gene–specific primers showed the occurrence of soxA, soxB, and soxY genes with a single band corresponding to length of 850, 460, and 360 base pairs, respectively. The integration of the S. olei strain 20UP7 with S° caused 21.7–25.4 % increase in the rice and wheat yield compared to the soil treated with S° alone. This study concludes that the S. olei, native to high saline–sodic soils can be utilized for improving the sodicity reclamation and plant growth promotion using elemental S based formulations.