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Susan Romano thinks that here plants might be suffering from a Molybdenum
>Are you likely to see a plant deficiency if your basic fertilizer lacks
>molybdenum? if so, how would it likely be manifested and is it possible to
>add it separately?
From the Plant Nutrition Lecture List, located at:
http://lurch.bangor.ac.uk/dj/lectures/plant%20nutrition/index.html, this is
what Molybdenum is used for in plants:
"Molybdenum is a structural component of the enzyme that reduces nitrates to
ammonia. Without it, the synthesis of proteins is blocked and plant growth
ceases. Root nodule (nitrogen fixing) bacteria also require it. Seeds may
not form completely, and nitrogen deficiency may occur if plants are lacking
molybdenum. Deficiency signs are pale green leaves with rolled or cupped
It seems that if you were growing beans or any of the other legume crops,
Molybdenum might become an issue, due to the possible need for it by
Nitrogen fixing bacteria. So far as I know, Azolla is the only common
aquatic plant which is associated with Nitrogen fixation, so it might be
needed for good growth of Azolla as well.
From Philip Barak, an instructor at the University of Wisconsin, I get the
http://bob.soils.wisc.edu/~barak/soilscience326/. Barak quotes from Epstein
(1965), who did studies on the relative concentrations of the various
essential elements sufficient for plant growth.
Element mg/kg Relative # of Atoms
N 15,000 1,000,000
K 10,000 250,000
Ca 5,000 125,000
Mg 2,000 80,000
P 2,000 60,000
S 1,000 30,000
Cl 100 3,000
Fe 100 2,000
B 20 2,000
Mn 50 1,000
Zn 20 300
Cu 6 100
Mo 0.1 1
Ni 0.1 1
These numbers are based on dry weight of plant material.
You can see that only one atom of Molybdenum is present for every million
Nitrogen atoms, so it truly IS a micronutrient.
With so little required, it is quite possible that sufficient Molybdenum
might be present as an impurity in the other constituents of a fertilizer
mix. I believe a while back you stated that you either use or used to use
Kent Marine "Freshwater Plant Micronutrient Supplement with Iron". It lists
Molybdenum as one of it's constituents (of course, no concentration is
given). Another possible source would be Fritted Trace Elements, from Green
Valley (see Steve Pushak's website for a source). FTE has 0.060% Mo (actual)
guaranteed. I suspect that most commercial micronutrient supplements would
have similar amounts of Mo incorporated in their makeup.