Orchid Pro Fertilizer - Orchid Board

Shawna · #1 03-02-2021, 07:20 PM

Hi,

I am confused about the PH of my fertilizer. I mixed just 1/8 of a teaspoon into 1 gallon of distilled water. I used my Ph meter and my Tds meter to measure this. The results are 4.5 PH and 73 TDS. That is way low for PH. Is it just the brand of fertilizer or what did I do wrong with it. The NPK is 7-8-6. This is Dyna-Gro.

estación seca · #2 03-02-2021, 07:27 PM

That kind of pH is common when mixing fertilizers in pure water. Dissolved minerals react to decrease pH changes, and pure water lacks the minerals. This is why MSU fertilizer blends come in one for pure water, and one for well water (with minerals.)

Your mix might be OK to use. Pick a plant growing well for you. Pour that fertilizer through the pot and collect the effluent. Chrck the pH of that. The potting mix has its own chemistry.

Shawna · #3 03-02-2021, 07:34 PM

I am growing mostly in semi hydro. I believe the leca is pretty much neutral so I guess I could try it and then catch some water when I flush the pot. I guess this fertilizer is not made for distilled water. I am experimenting with fertilizers right now. I was trying to find a fertilizer that i could use with my tap water but I don't believe that is possible. My tap water PH 7.8 TDS 267.

Ray · #4 03-03-2021, 09:01 AM

Measuring the pH of the reservoir contents can give confusing results. Because the LECA is chemically inert, it does nothing to buffer the conditions in the pot, meaning the plant and associated microbes can make it change pretty easily, and it can change drastically during a day, based upon what the plant is doing.

Flood the pot with your solution and wait 30 minutes. Then trickle about 50 ml (a 1.5 oz shot glass) of your distilled water over the medium surface and collect the overflow. That’ll give you the most accurate rhizosphere pH.

By the way, 1/8 tsp/gal of that fertilizer has a true TDS of about 60 ppm, so either your water isn’t really pure, or this is yet another case of “Don’t Trust your TDS Meter” for absolute values.

Shawna · #5 03-03-2021, 12:46 PM

Ray,

I took your advice but I guess I better study some more on how fertilizer actually works. The results of your test both PH and TDS has risen. The PH was 6.6 and the TDS was 138 so is that good or bad? I mostly have Cattleya alliance. Is there a better brand of fertilizer to use with distilled water. I know everyone says MSU for RO.

estación seca · #6 03-03-2021, 01:37 PM

Those numbers are fine. Fertilizer isn't as important as other aspects of orchid growing. I think it would be fine to use up what you have, do some reading, and buy something else once you understand more. That one could be used on other plants if you want to switch sooner.

Ray · #7 03-03-2021, 04:53 PM

Quote:

Originally Posted by Shawna

Ray,

I took your advice but I guess I better study some more on how fertilizer actually works. The results of your test both PH and TDS has risen. The PH was 6.6 and the TDS was 138 so is that good or bad? I mostly have Cattleya alliance. Is there a better brand of fertilizer to use with distilled water. I know everyone says MSU for RO.

The pH you measured was literally controlled by the plant and the microbes, and as estación seca said, it's fine. The TDS value is basically meaningless.

Personally, I prefer K-Lite fertilizer, because you're 1) not paying for water, 2) provides more Ca and Mg, both important when using RO, and 3) has the ions in the ratios that mimics what the plants see in nature.

Finish using the Dyna-Gro stuff, then you can switch. By the way, for plants in S/H culture, I'd recommend doubling the amount of that formula you're using.

Shawna · #8 03-03-2021, 09:02 PM

Sounds Good. Thanks a lot for the help

Orchid Whisperer · #9 03-04-2021, 06:24 AM

Hi Shawna

In terms of your pH and TDS, have you considered mixing a little of your local tap water in with your distilled water?

It would be good to know the quality of your tap water first, but even adding 10 to 25% tap water would increase the dissolved minerals that Estacion Seca was talking about, improving the pH buffering capacity.

I agree that your current fertilizer is probably fine. All plants need the N, P, and K macronutrients. All plants need N and K in approximately equal amounts.

Ray · #10 03-04-2021, 09:14 AM

Quote:

Originally Posted by Orchid Whisperer

All plants need N and K in approximately equal amounts.

Can we discuss that?

Tissue analyses suggest that the N:K ratio be more on the order of 10:1, and anecdotally, my plants have been getting that since December of 2011 without any signs of deficiencies or performance reduction.