Effect of wheat root exudates on mobilization of iron and zinc from calcareous soils

To study the influence of phytosiderophores (PS) released from some Egyptia n wheat cultivars on mobilization and absorption of iron (Fe) and zinc (Zn) from pre-amended calcareous soils, three selected wheat cultivars (Sids 10 , Giza 162, and Baniswaif 2) were used. The cultivars were pre-cultured for 17 days in nylon bags as the control root compartment (RC) and filled with fine sand and provided with nutrient solution +/- Fe-EDTA. The nylon bags with roots of the seedlings were brought in contact for further 4 days with pre-amended calcareous soils. DTPA-extractable Fe and Zn from amended calc areous soils with sludge was much higher than from untreated soils. Relativ e increases in extractable Fe or Zn were found in Fe-deficient wheat (-Fe p retreatment) compared with Fe-sufficient plants. The extractable amounts of Fe- and Zn-DTPA from different calcareous soils were affected by the dista nce from the central root compartment where minimum values were reached at distance of more than 4 mm. Release of PS and mobilization of Fe and Zn wer e highest with, Sids 10 and Baniswaif 2 cultivars while Giza 162 was lower particularly under sufficient seedlings. Moreover, increasing CaCO3 content in calcareous soils minimized the growth differences among wheat cultivars . The status of Fe and Zn contents was improved in roots compared with shoo ts during the 4-day growth period. Furthermore, nutrient status was general ly higher in soils amended with sludge compared with untreated soils. Sids 10 have the highest values of Fe content particularly under Fe-deficient co nditions while Giza 162 was inferior. Zinc content in Sids 10 was superior in high calcareous soil (53% CaCO3 content) while Baniswaif 2 was superior in low calcareous soil (14% CaCO3 content).