effect of plant growth promoting rhizobacteria (pgpr) and arbuscular mycorrhizae fungi (amf) application on distribution of zinc chemical forms in a calcareous soil with different levels of salinity

the low bioavailability of zinc (zn) is in calcareous and saline soil, therefore the study of chemical forms and bioavailability of zn in these soils is necessary to estimate the potential availability. the objective of this study was to evaluate the effect of plant growth promoting rhizobacteria and mycorrhizae fungi inoculation on the chemical forms of zn in a calcareous soil at different salinity levels after harvesting corn by a sequential extraction method. a factorial experiment as a completely random design with three replications was conducted in greenhouse conditions. the first factor consisted of three salinity levels (0, 15 and 30 meq salt kg-1 soil) and the second factor was microbial inoculation (without inoculation, glumus intradices, pesudomonas bacteria and fungi + bacteria). the results showed that increasing salinity levels increased the concentrations of soluble+exchangeable, carbonatic and manganese oxide fractions and the concentrations of residual and organic fractions decreased. by application of all microbial treatments, the concentration of soluble+exchangeable, carbonatic and manganese oxide fractions increased and the concentration of residual fraction declined. the higher increase of concentrations of soluble+exchangeable (101%), carbonatic (59.3%) and manganese oxide (100%) fractions were observed in co-inoculation of bacteria and fungi treatment. there were positive and significant correlation between soluble+exchangeable, carbonatic and manganese oxide fractions with dtpa extractable zn which indicating the role of these fractions in the supply of zn to plant. results showed that the salinity and biological treatments caused the redistribution of zn from low available fractions to high available fractions in soil.