the comparison of micro elements (mn, fe and zn) and heavy metals (co, cr and cd) in the soil of perennial farms of saffron (crocus sativus l.) in southern khorasan province

in order to study concentrations of soil micro and heavy metal elements in some saffron planting regions of birjand province, an experiment was performed as factorial layout based on a completely randomized block design with three replications at year 2013. treatments were three field ages (annual, triennial and quinquennial) and five saffron regions including aryan shahr, hosseinabad, khosef, golferiz and mahmoei. soil microelement and hevey methal concentrations such as fe, zn, mn, co, cr and cd of soil were measured. the results showed that the concentrations of fe, zn, mn and cr in soil were significantly affected by field age (p≤0.05). effect of planting region was significant on soil fe, zn, mn, co and cr concentrations (p≤0.01). interaction effects between field age and planting region were significant on fe, zn and co concentrations (p≤0.01). by increasing in field age soil zn concentration was declined and heavy metal concentrations such as co, cr and cd of soil were enhanced. mn concentration in the quinquennial fields was 29 and 34% higher than annual and triennial first fields, respectively. co content in the quinquennial fields was 53 and 46% higher than annual and triennial first fields, respectively. the maximum and minimum fe concentrations were observed with 1.65 and 0.77 ppm for the fields of khosef and hosseinabad, respectively. the highest and lowest fe concentrations were obtained with 2.436 and 0.77 ppm for the annual fields of khosef and hosseinabad, respectively. the highest co concentrations were recorded in hosseinabad and khosef fields with 8.7 and 4.31 ppm, respectively. thus, it is recommended to use ecological managemens such as reducing the application of chemical fertilizers and improving the organic fertilizers to decline the concentrations of these elements in saffron fields.