Role of Iron in Citrus Production
In citrus production, iron acts as a catalyst in oxidation/reduction reactions; is involved in respiration; photosynthesis; and the reduction of nitrate and sulfate.
It is also a cofactor in many enzymes.
Iron and yield
Iron deficiency is commonplace and widely recognized. The most obvious effects are restricted fruit set and reduced fruit size. This results in a lower yield, as you can see happening with navel oranges in Egypt.
Iron and yield
Trials in Egypt show that yield is reduced when iron is deficient.
Soil and Foliar applications
Trials with chelates (China, navel oranges) confirm that soil applications are more effective and provide bigger yield responses than foliar applications.
Iron and TSS
Iron also has a direct effect on crop quality improving the levels of total soluble solids in oranges and mandarins as well as increasing the TSS/Acidity ratio.
Iron and TSS in lemons and limes
In lemons and limes the effect is to reduce the TSS content, thereby boosting the acidity of these fruits.
Iron and vitamin C
Good iron nutrition also boosts the ascorbic acid content of mandarins and oranges.
Iron effect at growth stages
| Stage | Iron effect |
| Fruit Set | To maintain fruit yield and quality should be applied with each leaf flush |
| Post Harvest | When needed for post harvest foliage flush |
See more on Citrus Growth Stages.
General guidelines for Iron application
The form of applied iron used to correct any deficiency is important. Chelates are more stable across a wide range of soil pHs and should be the preferred form to correct long-standing annual deficiencies, particularly on calcareous soils. Trials with chelates confirm that soil applications are more effective and provide bigger yield responses than foliar applications.
Iron deficiencies in Citrus
Symptoms of iron chlorosis appear first on young shoots. Under severe deficiency, leaves almost turn white, are stunted, and drop prematurely. Fe-deficiency is most common on alkaline (high pH), especially those with free lime in the topsoil (e.g. Spain and Australia), waterlogged soils and those of low organic matter (e.g. sand-soaks in Florida). Deficiency is best treated by soil application with chelated forms of iron. Foliar sprays will alleviate transient iron deficiencies. Lemons are more sensitive to iron deficiency than oranges and grapefruit. Use tissue analysis to check for deficiencies.
