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.

[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.

[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).

[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).

[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.

[Ray]

A living plant is 95% water. About 4% is carbon and nitrogen, and all of the remaining elements make up that last 1%.

The vast majority of those elements are incorporated within the plant tissues, and are stored "for a rainy day" and to be shared with newly-growing tissue. Calcium, however, is quite immobile once incorporated, so must be provided regularly when the pant is growing.

Most well-, and municipal water supplies have plenty of calcium, but there are some exceptions, such as NYC and places where snow melt is a major contributor to the aquifer. And of course, users of RO, DI, or distilled water need to provide it, as well.

Here, on the southeast North Carolina coast, the water is pretty pure, and does contain reasonable calcium levels, but is very low in magnesium. My regular use of K-Lite (12-1-1-10Ca-3Mg) is plenty for my orchids, but my landscape plants get Epsom Salts regularly.