Control of iron chlorosis in apple trees with injections of ferrous sulfate and ferric citrate and with soil?applied iron?sul

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Abstract
Chlorotic ‘Red Delicious’ apple (Malus domestica Borkh) trees located in Utah County, Utah, were treated for iron deficiency through pressure injection and soil treatment in September, 1981. Injection treatments were either ferrous sulfate (FeSO4 · 7H2O) or ferric citrate (FeC6H5O7 · H2O) at rates of 100 ml of 1% solution per year of tree age. The soil treatment was surface‐broadcast acidified iron‐rich mining residue (iron‐sul) at approximately 1 kg per year of tree age. Chlorotic conditions were completely eliminated by the spring of 1982 by ferrous sulfate injection. Ferric citrate injection decreased, but did not completely eliminate iron chlorosis. Visual observations were similar in 1983. The iron‐sul treatment gave no apparent improvement of the chlorotic condition in the first season after treatment, and only slight improvement the second year. The improvement in chlorotic conditions gave correspondingly heavier fruit set, higher chlorophyll levels and greater shoot growth for trees injected with both ferrous sulfate and ferric citrate. However, even iron‐sul significantly improved shoot growth and chlorophyll content compared to the untreated control. Some injury at the injection site was observed for both injected compounds.