Role of Zinc Solubilizing Bacteria in Enhancing Growth and Nutrient Accumulation in Rice Plants (Oryza sativa) Grown on Zinc (Zn) Deficient Submerged Soil

Zinc (Zn) is a mineral that is required for normal plant and human metabolism; nevertheless, Zn deficiency in soil poses a significant threat to long-term agricultural productivity. In this investigation, the impacts of zinc solubilizing bacteria (ZSB) on Zn release, rice plant growth, and yield parameters in the Zn-deficient submerged soil were evaluated. The Zn solubilization capacity of five different bacterial isolates was tested, followed by an incubation study that was conducted for 9 weeks under the submerged condition in the Zn-deficient calcareous sandy clay loam soil. A field experiment was conducted in Zn-deficient soil with randomized block design and replicated thrice to find out the impact of two Zn sources, viz., zinc carbonate (ZnCO3) and zinc sulfate (ZnSO4) with the efficient ZSB on rice growth and Zn accumulation in the rice grains. Out of five tested bacterial isolates, Bacillus aryabhattai KSB N2K7 released the significantly higher amount of Zn in the liquid medium amended with insoluble Zn sources, such as zinc oxide (ZnO) and zinc carbonate (ZnCO3) of 185.7 mg L–1 and 185.4 mg L–1, respectively. The incubation study revealed that the application of ZnSO4 (25 kg ha–1) with B. aryabhattai KSB N2K7 showed a significantly higher range of Zn release (3.81 to 5.12 mg kg–1) during 9 weeks of incubation as compared with that of ZnCO3 (11 kg ha–1) with B. aryabhattai KSB N2K7 (3.52 to 4.48 mg kg–1). The application of Zn sources with B. aryabhattai KSB N2K7 resulted in a significant increase in plant biometrics. The application of 25 kg ZnSO4 per hectare with B. aryabhattai KSB N2K7 resulted in the significantly higher grain yield of 5806 kg ha–1 than that of treatment containing recommended dose of fertilizers alone. The application of 25 kg ZnSO4 per hectare with B. aryabhattai KSB N2K7 registered significantly higher Zn accumulation in grain compared to all other treatments. Thus, the results demonstrated the crucial role of Bacillus aryabhattai KSB N2K7 in Zn release and rice fortification in the Zn-deficient submerged soil.