| Resumo: |
Abstract: Pot experiments were performed in a greenhouse to compare zinc (Zn) and iron (Fe) sources: 1) corn plants were grown in a Zn-deficient soil and received a Zn fertilization (0, 1.9, 3.8, and 7.7 mg kg-1; equivalent to 0, 5, 10, and 20 kg Zn ha-1) as ZnEDTA and ZnSO4; 2) sorghum plants were grown in a soil where iron chlorosis symptoms had been observed and received a Fe fertilization (0, 1.5, 3, and 6 mg kg-1; equivalent to 0, 3, 6, and 12 kg Fe ha-1) as Fe-EDDHA and FeSO4. Corn dry matter (DM), Zn concentration, and Zn uptake were higher with Zn-EDTA as compared to ZnSO4. In the sorghum experiment the highest DM production was obtained with Fe-EDDHA, which increased Fe concentration and uptake in higher proportion as compared to FeSO4. However, only highest Fe rates eliminated Fe chlorosis. Residual soil DTPA-extractable Zn and Fe levels were higher for chelates in comparison to sulfates; the largest differences between sources were found at the highest Zn and Fe rates. Although sulfates needed higher rates to achieve similar effects, their benefit/ cost relationship was higher than chelated sources due to their lower cost. However, factors such as the residual effect of each source, crop sensitivity, and the value of the crop should be also considered when choosing a Zn or Fe fertilizer source for similar soils.
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