Soil-agrochemical aspects of remediation of copper-contaminated soil in applying growth-promoting rhizosphere bacteria

Impact of introducing growth-promoting rhizosphere bacteria of genus Pseudomonas on growth and chemical composition of spring wheat plants in artificial contamination with copper nitrate in increased quantity, at rate of 300 mg/kg of humus horizon of agro-gray soil (Luvic Retic Greyzemic Phaeozems (Loamic)) in pot experiment was studied. Applying bacteria P. fluorecens SV20, P. fluorecens SV21 and P. putida SV23 reduced significantly copper toxicity on plants in first half of growing season. Increasing plant resistance to application of copper nitrate in using bacteria was due to increase in their biophilic elements N, P, K, Ca, Mg, Fe, Mn and Zn uptake from contaminated soil without significant changes in concentrations of most elements in plants and in soil medium reaction. Positive effect of bacteria was also associated with increase in copper uptake by roots – increase in barrier ability of root system towards metal. Bacteria increased presence of copper in soil mainly in specifically sorbed and associated with ferruginous minerals fractions, and, to a lesser extent, in fraction associated with organic matter, and decrease metal in residual fraction firmly associated with clay minerals in extraction by sequential selective extractions method. Bacteria enhanced phytoextraction – purification of contaminated soil, increasing copper uptake by plant shoots. Application of bacteria can be recommended in developing strategies for remediation of copper-contaminated soils based on environmentally friendly technologies.