Tomato acquisition of iron from iron chelates in a calcareous sandy substrate

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Abstract
Iron (Fe) is often applied as Fe‐chelate in fertirrigation for drip irrigation systems, but the high cost of its application makes it necessary to study its behavior in the substrates used in drip irrigation. Laboratory and pot experiments were performed to study the behavior of some commercial Fe chelates in a calcareous (11% CaCO3) sandy substrate ("sand of Palomares") widely used for drip irrigation. In a pot experiment, the effect of humic acid on the uptake of Fe from commercial Fe chelate (EDTA) by plants was also studied. Iron chelates comprised of EDDHA or EDDHMA maintained higher percentages of chelated Fe in solution after interaction with “sand of Palomares”; than Fe chelates of EDTA. In the pot experiment, Lycopersicon esculentum Mill. cv. Rambo were grown on “sand of Palomares”; with different commercial Fe chelates as sources of Fe. Humic acid and a mixture of humic acid and commercial Fe chelate (Fe‐EDTA) were also included in the experiment. Commercial Fe‐EDDHMA was the best source of Fe for the tomatoes in this study. The mixture of commercial Fe chelate (EDTA) and humic acid produced an increase in the content of Fe and manganese (Mn) in shoots and of potassium (K) and zinc (Zn) in roots.