MSU R/O - Do I need add'l MgSO4?

[D_novice]

Greetings, I use MSU rain/city water formula (with either rain or city water, depending on the time of the year). I use 1/2 tspn gallon in the growing months to get a TDS of about 300. I also do water leaches, and sometimes do Ca Nitrate, Seaweed Extract, or Pro-Tekt silicon formula instead of MSU. I have a pretty varied collection: Paphs, Phrags, Oncdm alliance, Cymbidium, Catt, Encyclia, Laelia anceps, a handful of Phals and AU Dens.

That formula is 2% Mg and 10% Ca.

Do you think I need additional epsom salts? I was hoping that making MSU my regular formula would mean I could skip that.


My water specs: 7.0-7.2 pH, 90-ish ppm TDS, .14 mS EC, and 60 PPM alkalinity. (First 3 measurements with Milwaukee Instruments 802 meter, alkalinity with LaMotte kit. Have to double check the alkalinity, wouldn't swear I was using the test properly when I checked that.)

[Ray]

Use the MSU RO formula regularly, and don't add calcium nitrate, mag sulfate or Pro-Tekt.

Pro-tekt, by the way, can raise the pH drastically.

I don't know what seaweed extract you're using, so cannot advise about that.

[camille1585]

Doesn't MSU fertilizer contain calcium and magnesium anyway? I got the equivalent of MSU here from a belgian supplier, and both are included. I don't think there would be need to add more.

[Intruder]

Originally Posted by camille1585

Doesn't MSU fertilizer contain calcium and magnesium anyway? I got the equivalent of MSU here from a belgian supplier, and both are included. I don't think there would be need to add more.

It is a bit low in magnesium. I preferred a ratio Ca/ Mg of 3. Some members of my club have experienced a yellowing of the leaves with AK..RM.

[D_novice]

I adjust pH of the irrigation solution for Pro-Tekt and Seaweed using citric acid, though I used them for a long time without doing that. Also, I probably use those 1x every other month.

I've started using Bill Argo's method of testing substrate conditions, and so far they are all mildly acidic - not quite the 5.8 - 6.2 pH he recommends.

[DeaC]

Sitting here reading off the label of MSU Pure Water...Mg=2.6,Ca=8.0.

[D_novice]

There are slightly different products marketed as MSU, apparently. (?) Mine is the original GreenCare from Jim's Orchid Supplies.

[Ray]

Originally Posted by D_novice

There are slightly different products marketed as MSU, apparently. (?) Mine is the original GreenCare from Jim's Orchid Supplies.

The Greencare-made material is sold by several good supply houses. Orchidmix.com has his own, similar formula made.

I recommend that folks avoid RepotMe.com, as their liquid version is made by dissolving one pound of the original granular material in a gallon of water, making it a roughly 1.4-0.3-1.6-3Ca-0.3Mg formula, even though they illegally label it as the formula of the granular stuff (and you have to pay their exorbitant shipping rates for water).

[Orchid Whisperer]

I agree with skipping the added Ca and Mg, since it is in your fertilizer. There is a good chance it is also in your tap water.

Know the signs of Ca and Mg deficiency in orchids (easily found with a Google search). It is unlikely you will get those symptoms, but in the event that you do, and can't rule out other causes, then you can add a little Ca and Mg supplementation back into your growing regimen (go easy; don't over-do it).

[D_novice]

A couple of different semi-famous cymbidium growers have come to talk to our society and mentioned various augmentations to their fertilizer regime, including CaNO3-. (Neither of them uses MSU.) Cymbidium are known as heavy feeders, and what works for Cyms might not work for other plants. However one of the speakers said he thought N and Ca were the most important elements for orchids, which is the origin of using that.

Also, no one is advocating using a lot or overdoing it. The idea is to complement a regular, balanced fertilizer like MSU; to apply any additions during growing season; and to do so at the correct dosage based on one's water source and measurement of TDS/EC/pH.

Of course, there are plenty of successful growers, including of Cyms, that don't even feed them! So, everyone finds out what works for them. And, you have a better chance of stumbling on something helpful if you experiment. Ray's SH system is the poster child for that, if I'm not mistaken.