Comparative efficacy of citric acid and Fe(II) Sulfate in the prevention of chlorosis in orange trees (Citrus sinensis L. cv ‘Darabi’)

Abstract

A field experiment was carried out comprising foliar spray of citricric acid and Fe(II) sulfate alone and in combination with citricric acid were applied to evaluate the recovery of iron chlorosis of orange trees (Citrus sinensis L. cv ‘Darabi’ , grafted on Citrus aurantifolia L.) grown on a calcareous soil. The treatments were Fe(II) sulfate (500 mg Fe/L), citric acids plus Fe(II) sulfate (1000 mg/L + 500 mg Fe/L), citric acid (1000 mg/L), and distilled water as a control. A non-ionic wetting agent was used in all treatments. The use of frequent foliar sprays alleviated Fe chlorosis in orange trees. On 4 of 7 measurement dates, trees in the citric acids plus Fe(II) sulfate treatment had higher leaf chlorophyll indexes determined with a SPAD meter (SPAD values) than trees in all other treatments. Trees in the Fe(II) Sulfate treatment had higher SPAD values than trees in the citric acids and control treatments. Total leaf iron content was higher for the citric acids plus Fe(II) sulfate and Fe(II) sulfate treatments than the citric acids and control treatments. There was a difference in total leaf iron content between the citric acids and control treatments. Sprays of citric acids plus Fe(II) sulfate improved fruit size and quality compared to fruits of control trees. Sprays of Fe(II) sulfate also improved fruit quality and increase fruit size. Sprays of citric acids also improved fruit size and quality compared to fruits of control trees. These results suggest that foliar sprays with Fe could help to avoid yield and quality losses caused by Fe chlorosis in citrus orchards. Furthermore, these treatments could be done with relatively cheap materials such as solutions containing Fe(II) sulfate.