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Doctor of Philosophy




Corn yield responses to Zn fertilization were not obtained in any of 11 field experiments located on soils containing from 0.4 to 1.0 ppm of DTPA extractable Zn (DTPA-Zn). All Zn treatments increased the Zn concentration of corn leaf samples collected at silking time. However, broadcast applications of inorganic Zn sources did not raise the Zn content of leaf tissue above 20 ppm in some of the tests located on calcareous soils. A liquid inorganic Zn compound tended to be more effective than grandular ZnSO(,4) in supplying Zn to corn plants. On calcareous soil, band placement of ZnEDTA near the row at rates of 2.2 and 4.5 kg Zn/ha increased leaf Zn levels about as much as 11.2 and 22.4 kg rates of inorganic sources applied broadcast;Regression analyses indicated that Zn application rate and soil pH were the factors most closely related to Zn uptake by corn plants growing on fertilized plots (R('2) = 0.855). Plant uptake of inherent soil Zn from untreated soils was largely influenced by DTPA-Zn, organic C (OC), and soil pH (R('2) = 0.769);The level of DTPA-Zn in each soil profile was found to be at a maximum near the surface and to decline with depth. Larger differences in maximum and minimum DTPA-Zn values were observed in the more developed soils. Total soil Zn levels were positively correlated with OC and negatively correlated with CaCO(,3)-equivalent to varying degrees, depending on soil development and parent material;In greenhouse studies, treatment of calcareous soil with liquid ZnEDTA (5 mg Zn/kg soil) increased Zn uptake by corn plants more than did equivalent applications of liquid ZnSO(,4). The advantage for ZnEDTA was greater with an unincorporated surface placement than with an incorporated placement. The two sources were of about equal effectiveness on neutral soils and ZnSO(,4) was more efficient on a slightly acid soil.



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Martin Peter Mascianica



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149 pages