Fertilizer In Solution vs Dry Mix

[jmrathbun]

I've experimented with a number of popular fertilizers, including the MSU and K-lyte formulae as well as balanced mixes. I've been buying the dry mixes to save money, but I notice the mixes often segregate in the package with fine particles on the bottom and larger ones above. A neighbor in the business used to sell MSU in solution but no longer does.

Do you have recommendations for formulating a concentrate from MSU or another popular mix that I could store in quart containers and add to my one-gallon watering can? My orchids are mostly Phals, Paphs, and Catts with occasional Oncidiums and Dendrobiums.

[Orchid Whisperer]

The water soluble granules may separate by particle size, but I'm unaware of any reason why the small particles would have a different composition from the large particles. You could certainly make small batches of liquid concentrate from the granules, but you would need to work out the chemistry of the liquid concentrate to avoid over-fertilizing your plants. IMO the granules are way easier to work with.

[jmrathbun]

Maybe I just need to agitate the mix before dipping, but the different-sized particles sure look to my chemist's eye like different components of the mix.

[Ray]

You're "chemist's eye" is right.

The Greencare formulas (MSU & K-Lite) are manufactured in a factory that usually deals with large-volume users - multiple bags at a time - so the segregation of minerals is meaningless. Because of that, you'll see large flakes of one material and small prills of another, and fine powder of yet others, and it may change from lot to lot within the same formula.

For we smaller users, I suggest that you make a liquid concentrate using a significant part of-, or all of a jar, then use that to let down for the final solution.

For example, for a 100 ppm N final solution of MSU RO or K-Lite, it requires 2.9g/gallon. Let's assume you will mix one fluid ounce of your concentrate to make up that gallon, so the concentrate will need 2.9g/oz, or 2.9 x 128 =371.2g/gallon.

Two pounds is 908g, so you could make 908/371.2=2.45 (call it 2.5) gallons of that concentrated solution per jar of powdered fertilizer, then use one ounce for each of the 320 gallons of solution to be applied.

[Orchid Whisperer]

I stand corrected. Ray certainly has more experience with K-lite and MSU than I do.

If we were talking about other formulations that don't contain the flakes, prills and powders, that would be a different matter.

[jmrathbun]

It's been a LONG time since I did much actual chemistry, so I needed considerable work to check Ray's calculations as they might apply to my situation. I'll show my results in case anybody wants to check my math, and perhaps to be helpful to anybody else with a similar situation:

I have a bag of MSU RO weighing 18 oz that I wish to make into a solution of 125 PPM Nitrogen (for use over Orchiata).

MSU RO is 13% nitrogen by weight.

18 oz = 510 g x 0.13 = 66 g of N in the bag.

If I mix the bag's contents with a gallon of water, the concentration of Nitrogen becomes 66 g/gal.

One gal of water is about 3785 g so the concentration of N is 66/3785 = 0.0175 = 17.5 ppt = 17,500 ppm.

17500/125 = 140 doses in my gallon jug.

1 gal = 128 oz so each ounce contains about 1.09 doses (less if I overfill).

My watering can holds about 17.25 cups, about 8% larger than a gallon, so one ounce of mix should be about perfect!

Since a gallon of the mix will last me more than a year, I wonder how long will this stuff remain stable at room temperature? Do I need to add disinfectant or an anti-fungal to discourage biota?

[astrumes]

I know this thread is a few years old but I wanted to bump and see if anyone had an answer to the last question.

I use the granular MSU formula and I'm noticing the difference in the small batches.

If I decided to mix the whole 8oz jar in a gallon of water to dose out over the course of the year, how long would the mixture stay shelf stable @ room temp? Assuming I used an opaque jug and R/O water to mix of course.

Would fungus or mold forming in the jug be an issue? What should I use to negate biota?

[jmrathbun]

Since I last posted here, I've been using 1 tsp of MSU-RO formula in a gallon of water weekly. Mos of my Phals get an additional weekly watering without additives, but the Catts seem happy with once-a-week watering in the relatively cool, humid environment of my basement growing area. I'm also using a tablespoon of Kelpmax in a gallon of water monthly with the fertilizer. Hard to know for sure with orchids, but they seem healthy and virtually all of my phals are either in bloom or in bud atm. The medium is still mostly Orchiata, and I think that stuff typically needs more water than other bark mixtures I've used. I have a few Phals in their original moss which also seem to be doing fine; they only get watered once a week, as the moss stays damp. What facilitates things imo is that the MSU supplied by 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 usual, just finer milled. There is a minimal amount of dust and otherwise no particles that seem very different from one another. This makes me a lot more confident that I can prepare one gallon a week without a lot of variation that I saw with other preparations that tended to settle and separate.

[Ray]

I agree that the fertilizers (I only sell K-Lite, but it's from the same factory) have become far more uniform than they used to be.

Back to the stability question, the answer is "it depends". The more dilute you make it, the longer the calcium will stay in solution.

Will it grow bacteria? Yes. Add some Physan if you feel it's really necessary.

[astrumes]

Thanks for the input and giving an update!

I'll take what you guys have posted into consideration and perhaps make a small batch and see how it lasts.

Ray, I've ordered a bottle of your klite and can't wait to try it!