Prevention of iron-deficiency induced chlorosis in kiwifruit (Actinidia deliciosa) through soil application of synthetic vivianite in a calcareous soil

In this study we have tested the hypothesis that lime-induced Fe deficiency chlorosis of kiwifruit may be prevented by the application of a synthetic iron(II)-phosphate analogous to the mineral vivianite [(Fe 3(PO4)2·8H2O)]. Two experiments, under greenhouse and field conditions, were performed. In the greenhouse, 1-year old micropropagated plants (Actinidia deliciosa, cv. Hayward), grown in 3-L pots on a calcareous soil, were treated in early autumn with soil-applied: (1) synthetic vivianite (1.35 g plant-1) and (2) Fe-EDDHA (24 mg Fe plant-1). The synthetic vivianite suspension, prepared by dissolving ferrous sulfate and mono-ammonium phosphate, was injected into the soil as a sole application whereas the Fe-EDDHA solution was applied four times at weekly intervals. The field experiment was conducted in a mature drip-irrigated kiwifruit orchard located on a calcareous soil in the Eastern Po Valley (Italy). Treatments were performed in early autumn by injecting synthetic vivianite (1.8 kg tree-1) and Fe-EDDHA (600 mg Fe tree-1) into four holes in the soil around each tree, at a depth of 25-30cm. The Fe-chelate application was repeated at the same rate in the following spring. Untreated (control) plants were used in both experiments. Autumn-applied Fe fertilisers significantly prevented development of Fe chlorosis under greenhouse conditions whereas in the field only vivianite was effective. In conclusion, these 1-year results show that vivianite represents an effective alternative to soil-applied Fe chelates for preventing Fe chlorosis in kiwifruit orchards.