Acidic MSU-RO Solution Precipitates

[jmrathbun]

Thanks! I did some more research and found that available formulations of the MSO-RO vary in how finely the particles are milled, with one source asserting that the finer-milled products are less subject to sorting in the package (which was my original problem). I decided to try a different brand that claims to be superior in this regard and can post further when it arrives.

[Ray]

The issue is that the producer of these fertilizers primarily cater to large-scale, commercial operations that usually mix up solutions from several bags at a time. Because of that, they don't "mill" it at all, but blend the raw materials to give the proper chemistry, not texture. On top of that, the same chemical raw materials can be powder, granular, prills, or flakes, depending upon the manufacturer, and that can affect the texture, too.

Pretty much everyone buys from them and repackages....

[jmrathbun]

The new bag of MSU-RO from Jim's Orchid Supplies in Ft Pierce, Fl, appears much more homogeneous than what I had before. It has exactly the same analysis and ingredients as posted above, just finer milled. There is a minimal amount of dust and otherwise no particles that seem very different from one another. It has the standard labeling of 1 tsp per gallon.

The information I've found on orchid nutrition is incredibly variable. To quote one source:

"Orchid growers need to include the frequency of feeding in the estimates, with 250 ppm N being common for bi-weekly feeding, 100 ppm N if you feed weekly, etc. At First Rays, we shoot for roughly 30-50 ppm N, and feed at that rate at every watering." Orchid Fertilizer Basics - Garden & Greenhouse

MSU-RO is 13% nitrogen by weight, all of it soluble. The package I got weighs 475g and measures 13 fl oz.
That's 475g x 0.13 = 62g of nitrogen per 13 fl oz, or 4.75g per one fl oz. One tsp is about 0.17 fl oz, so 0.17 x 4.75 = around 0.8g of nitrogen per tsp. A gallon of water weighs about 3780g at room temperature, so mix 0.8g nitrogen into 3780g of water and you get around 0.00021 or 210ppm. That would suggest 1/2 tsp of dry mix per gallon of RO water for my weekly feeding schedule.

[Ray]

Actually, since writing that, I decreased my feeding to about 25 ppm N, using K-Lite (a 12-1-1-10Ca-3Mg derivative of MSU RO). Still at every watering, and supplemented monthly with KelpMax @ 1 tablespoon/gal and Inocucor @ 3 tablespoons per gallon. The growth and flowering is so much better than I have ever experienced that I highly recommend that regimen.

While I'm not formally educated in the field, I've been doing a lot of research into plant nutrition, and have tailored my regimen to match what I've learned. One of the things I've learned is that fertilizer simply isn't all that important!

We read all of the lore - and some actual facts - about feeding, but we ignore the fact that those are primarily based upon food crops, and that simply does not translate well to orchids.

One of the "universal constants" (not absolute, but the closest to that I've seen) is that it takes about 5 grams of mineral nutrition for a plant to add one pound of mass. For a restepia in a 4" basket, that might be decades of growth. For a cattleya in a 8" pot, maybe two or three years. For corn, on the other hand, a single seed may become 5-pounds of vegetation and fruit in a single, 90-day period.

Nutrition is critical for the corn; not so much for orchids.

I have concluded that if you fed a little bit, that's good enough. The OCD scientist in me forces me to pay closer attention, so that's what I do!

[jmrathbun]

I was very interested in the K-Lite idea, which I read about a couple of years ago in Orchids. I wasn't very happy with the outcome: my spikes seemed stunted compared to before and after. It may be my dose was insufficient for the circumstances.

A well-known California grower followed me onto the rostrum when I presented K-Lite to our local society. He made clear that his experience was superior to mine and he always used a rich concentration of balanced fertilizer in his greenhouses, followed by a copious rinse. I wasn't in a position to challenge his authority, but I was thinking, "So he gives his plants more nutrients than they can use, then uses a lot of scarce California fresh water to flush the extra nutrients into the water table. How smart is that?" Of course I don't have a greenhouse and my basement growing room has no drain in the floor.

Orchid culture seems still more of an art than a science, not unreasonably considering all the uncorrelated relevant variables: growing media, temperature, humidity, light (quantity and quality), water quality, fertilizer and other additives, plus 25,000 naturally occurring orchid species and over 100,000 registered hybrids (and those are old numbers), and the fact that the little critters are so slow to indicate their preferences.

There's always a price to be paid for the worship of beauty. Thanks for volunteering so much time here!

[Ray]

I think orchid growing is science - probably scientifically analytical observation, more than anything - but we just haven't learned it well enough yet!

Don't forget; science to the uneducated looks like magic!

I am grateful for the folks that spend their time researching and just plain thinking about these things, and sharing them like this, as they realize that there are no hard-and-fast answers to orchid-culture questions that start with "what's the best...".