The effect of biofertilizers, humic acid and superabsorbent polymer on cadmium uptake and remediation by annual medic (Medicago scutellata L.)

This study was carried out to investigate the effect of single and combined inoculations of plant growth promoting rhizobacteria (PGPR)، mycorrhiza fungi، humic acid and super absorbent polymer on growth and uptake of cadmium in annual alfalfa (Medicago scutellata). The experiment was done at the research greenhouse of Islamic Azad University – Karaj branch during 2009-2010 in factorial design as a completely randomized design (CRD) with four replications. The first factor was levels of Cadmium [0- 40 - 80 mg kg-1 soil cadmium chloride (CdCl2)] and the second factor included treatments (inoculation of PGPR، mycorrhiza fungi، humic acid and superabsorbent polymer) separately and combined with 16 levels. Biofertilizers used in this experiment were bacterial species (Azotobacter chroococcum)، (Azospirillum lipoferum) and (Pseudomonas putida) in a mixture form and mycorrhiza fungi was (Glomus intraradices). Results showed that with increasing cadmium concentration in soil، the accumulation of cadmium in shoots and roots and available cadmium in soil increased. Interaction of factors indicated treatments b12، b13، b14 and b15 had the highest rate of Cd accumulation in shoots (62 percent higher than the control). treatments including combined use of PGPR، mycorrhiza fungi and superabsorbent polymer showed the highest cadmium uptake by the root (42. 3 percent higher than control). Combined use of biofertilizers، superabsorbent polymer and humic acid increased transfer factor (TF)، accumulation factor (AF) and enrichment coefficient (EC). Overall results indicated that application of PGPR، mycorrhiza fungi، Humic acid and superabsorbent polymer effect on Cd uptake in shoots and roots of annual medic. These materials can move toward success phytoremediation of contaminated area with heavy metals.