Two preliminary experiments were conducted to investigate the effect of Mn
concentrations on the performance of soybean in two different soil types induce
activation and those which are harmful to soybean plants and Bradyrhizobiu
japonicum cells in the first experiment sequential concentrations of Mn (from zero to
500 ppm) to clay soil planted wilh soybean in small pots. The second one carried out
oy addition of some selected Mn concentratlens resuued from the first experirnent
(zero, 100, 500, 1000, 2500, 3000 and 5000 ppm) to "asks containing yeast mannitol
medium, then inoculated with Bradyrhizobium japonicum (5t 110) cells. In the main
pot experiment clay and calcareous soils were used. A sequential concentrations 0
Mn were added to both soils (zero, 300, 500, 1000 and 2000 ppm) In presence or
absence of rhlzobial inoculation. The results indicated that all Mn concentrations had no obvious significant
effects on germination % and natality %. EmbryoniC intemod and snoot length were
significanUy increased till concentrations .,00 and 1500 ppm for each respectively.
Viable counts of rhizobial cells significantly increased due to low Jevels of Mn (100
and 500 ppm), but heavily significant decHnes were recorded when concentrations
above 500 ppm were applied. Rhlzobial inoculaUon significantly increased seed yield
and most of other growth parameters. Soil types neither affects crop yield nor P and
K contents of seeds. Plants which were grown in clay soil exhibited an increase in N-
content than In calcareous soil. NOdules had no consistent effects due to increasing
Mn levels. While N·contenl of plants significanUy declined. K-content exhibited nearly
similar trend. However, P-content generally did not affected. In the clay soil, all Mn
concentrations {ill 1000 ppm did not significantly affect seed yield or Inoculated plants
but a significant increase was observed at 2000 ppm. In calcareous soil, the addition
of manganese caused non- Significant decrease in seed yield, Inoculation with
rhizobia obviously decreased Mn uptake by plant in both soil types.