TOMATO ACQUISITION OF IRON FROM IRON CHELATES IN A CALCAREOUS SANDY SUBSTRATE

Iron (Fe) is often applied as Fe-chelate in fertirrigation for drip ir rigation systems, but the high cost of its application makes it necess ary to study its behavior in the substrates used in drip irrigation. L aboratory and pot experiments were performed to study the behavior of some commercial Fe chelates in a calcareous (11% CaCO3) sandy substrat e (''sand of Palomares'') widely used for drip irrigation. In a pot ex periment, 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 so lution after interaction with ''sand of Palomares'' than Fe chelates o f EDTA. In the pot experiment, Lycopersicon esculentum Mill. cv. Rambo were grown on ''sand of Palomares'' with different commercial Fe chel ates as sources of Fe. Humic acid and a mixture of humic acid and comm ercial Fe chelate (Fe-EDTA) were also included in the experiment. Comm ercial Fe-EDDHMA was the best source of Fe for the tomatoes in this st udy. The mixture of commercial Fe chelate (EDTA) and humic acid produc ed an increase in the content of Fe and manganese (Mn) in shoots and o f potassium (K) and zinc (Zn) in roots.