Molybdenum in nutrient formulations.

[DavidCampen]

I was comparing the ratios of various elements in the Dyna-gro Orchid-Pro formulation versus an MSU RO water formulation. I obtained both formulations from Jim's Orchid Supplies:

Dyna-gro Orchid-Pro

MSU: SPECIAL ORCHID FERTILIZER. 13-5-15. RO, RAIN or TAP WATER FORMULA!

The ratio of the various elements looks about the same in both formulations when comparing the trace elements to calcium/magnesium, varying at most by about a factor of 2, except for molybdenum. The MSU formulation has about 20 times as much molybdenum.

Does the MSU formulation really call for this much molybdenum. If so is the Orchid-Pro formulation seriously deficient in molydenum?

Here are the ratios:
..........OrchidPro......MSU
Ca.............4..............4
Mg.............1..............1
Fe.............0.2...........0.35
Cu.............0.1...........0.09
Mn.............0.1...........0.18
Zn.............0.1............0.09
B...............0.04..........0.04
Mo.............0.0018.......0.04

[PaphMadMan]

Molybdenum is needed in such small quantities that deficiency is somewhat unlikely except in completely artifical conditions - mineral poor media, RO water, no insects, no bird droppings, etc. The MSU fertilizer is formulated for use with RO water. As far as I know the Dyna-gro is not. Any other water source (ground or surface water, collected rain) is likely to contain some molybdenum naturally. Regardless, the Dyna-gro formulation likely contains enough molybdenum to avoid deficiency in almost all situations, while the MSU formulation likely contains little enough to avoid molybdenum poisoning in any normal situation. As you noted, they are otherwise similar in calcium, magnesium and micro-nutrient content, so either is a valid choice in most cases.

[Shiffdaddy]

Its about as common as Zinc deficiency

[DavidCampen]

I notice that the Orchid-Pro formulation lists chlorine (chloride) at the same percentage as iron and twice that of sulfur, copper or manganese while the MSU RO water formulation lists none. Chloride is recognized as an essential element in plant nutrition:
http://www.ksre.ksu.edu/library/entml2/mf3001.pdf
The link above comments that plants may take up as much chloride as sulfate. It makes sense to me that plants would require an anion other than nitrate that forms soluble salts, many salts of the only other anions in nutrient formulations, sulfate and phosphate (and also borate and molybdate), are insoluble.