In the years 2005 and 2006, spring and autumn experiments were carried out with greenhouse lettuce ‘Michalina’ cultivar, which was fertilized with three iron chelates, i.e.: Fe-DTPA, Fe-EDTA+DTPA, Fe-AM-4 in the following doses (mg Fe·dm^-3): 20  (control), 50, 75, 100 and 125. The objective of the work were the after effect of the mentioned chelates investigated in the autumnal experiments. Containers with peat that were used in spring experiments were stored in the greenhouse until autumn. In mid-September, lettuce seedlings were planted into the stored peat-filled containers after supplementation of the macro- and micro-elements with the exception of iron. No negative action of chelates was found. Plants yielded well without any symptoms of chelate excess which were observed in spring. After the application of the studied chelates, independent of the levels of Fe, the lettuce yields were similar. Increasing Fe levels, independent of chelates, were accompanied by a similar Fe content in leaves, by an increasing content of copper and decreasing contents of manganese and zinc.

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