Relation between Zinc Fractions and Bean (Phaseolus vulgaris L.) Indices in Some Calcareous Soils Amended and Un-amended with Sewage Sludge

Investigation of the distribution of zinc (Zn) fractions in the soil allows determination of their bioavailability. In this research، 10 calcareous soil samples were selected and sewage sludge-amended (1% w/w) and un-amended soils were incubated for 1 month. Before planting، Zn was fractioned (exchangeable، associated with carbonates، associated with organic matter، associated with Fe and Mn oxides، and residual). Then، seeds of bean were planted in each pot. After 8 weeks، the aboveground parts of plants were harvested and Zn concentration، yield، and Zn uptake indices were determined. The results showed that all Zn fractions were increased by sewage sludge addition. Results of pot experiment indicated that significant correlation was found between Zn concentration، yield، and uptake in bean with Zn associated with Fe and Mn oxides (r=0. 80**-0. 89**) in un-amended soils. Moreover، yield was significantly correlated with all fractions (except Zn associated with Fe and Mn oxides) in the amended soils. Also، significant correlation was found between response and relative yield indices and exchangeable. The results of this research showed that availability of Zn fractions was different in un-amended and amended soils under bean planting.