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used by plants:
(ferrous) or Fe3+ (ferric). Fe3+ must, however,
be reduced to the ferrous form before uptake can occur.
component in the formation of chlorophyll (80% of Fe in plants is
located in the chloroplasts)
of many biochemical processes (found in ferredoxin, and enzymes such
as peroxidase, catalase, and cytochrome oxidase which participate in
foliage range for apple leaves:
most test methods don't distinguish between the forms of iron and
therefore, have little meaning for plant nutrition.
is strongly sorbed by soil components and is relatively immobile.
increase with increase in soil pH.
symptoms: Younger leaves are affected first and will show
Veins remain green except in extreme cases.
Shoot growth is stunted and twig dieback may occur.
Necrosis of tips and margins as deficiency progresses.
All or part of a tree may be affected.
May occur sporadically throughout orchard.
risk of Fe deficiencies on:
receiving excessive amounts of irrigation water, especially in early
spring when soils may still be frozen (see
of poor soil aeration (explain this chemically)
of N fertilizer may increase the chlorosis
and water management
soil drainage by soil profile modification or installing tile
irrigation water amounts and scheduling; and/or
banding of Fe-containing chemical amendments
foliar sprays (effect usually only temporary)
injection with Fe-compounds
Excess problems/Interactions with other
- Excess zinc, manganese, copper,
molybdenum, or phosphate encourages iron deficiency.
- Excess iron may reduce manganese
- In neutral to alkaline soils with low
available iron, increased acidity from ammonium fertilizer forms may
enhance the availability of ferrous (Fe2+) iron by promoting the
reduction of the unavailable ferric (Fe3+) iron.
updated: 14 February, 2001