Iron (Fe) deficiency
Pronounced interveinal chlorosis similar to that
caused by magnesium deficiency but on the younger
leaves.
Leaves exhibit chlorosis (yellowing) of
the leaves mainly between the veins, starting with the
lower and middle leaves.
Caused by factors that
interfere with iron absorption of roots: over
irrigation, excessive soluble salts, inadequate
drainage, pests, high substrate pH, or nematodes. This
is easily corrected by adding an iron supplement with
the next watering.
Fe is unavailable to plants
when the pH of the water or soil is too high. If
deficient, lower the pH to about 6.5 (for rockwool,
about 5.7), and check that you're not adding too much P,
which can lock up Fe. Use iron that's chelated for
maximum availability. Read your fertilizer's ingredients
- chelated iron might read something like "iron EDTA".
To much Fe without adding enough P can cause a
P-deficiency.
Note that when adding iron to the
solution, it is often necessary to not use fertilizer
for that watering. Iron has a tendency of reacting with
many of the components of fertilizer solutions, and will
cause nutrient lockup to occur. Read the labels of both
the iron supplement and the fertilizer you are using
before you attempt to combine the two.
Excess accumulation is rare but could
cause bronzing or tiny brown spots on leaf surface.
Manganese is involved in the oxidation reduction process
in the photosynthetic electron transport system.
Biochemical research shows that this element plays a
structural role in the chloroplast membrane system, and
also activates numerous enzymes.
