Remediation of Cadmium-Polluted Soil Using Plant Growth-Promoting Rhizobacteria and Natural Zeolite

— The impact of two strains of Pseudomonas bacteria and natural zeolite on the growth and elemental composition of barley plants was studied in an agrogray soil (Luvisol) artificially contaminated with cadmium in pot experiments. Application of P. fluorescens 21, or P. putida 23, or zeolite eliminated the heavy metal toxicity for plants. The cumulative effect of co-application of P. fluorescens 21 and zeolite was insignificant. The bacteria- or zeolite-mediated plant tolerance to cadmium was attributed to the enhanced root system development, decreased cadmium translocation into the roots, and improved mineral nutrition of the plants. Elevated nutrient uptake by the plants under the influence of bacteria and zeolite was the result of plant growth stimulation without significant changes in the concentrations of macronutrients N, P, K, Ca, and Mg, as well as Fe and micronutrients Zn, Mn, and Cu in plant tissues, including grain. Application of P. fluorescens 21 enhanced the Cd fixation in the soil organic matter in the first half of the growing season, which could be due to the metal sequestration by bacterial siderophores. Thus, application of the bacteria and natural zeolite can be recommended in the strategies for Cd-polluted soil remediation based on environment-friendly technologies.