Pot Flushing Experiment

[Ozpaph]

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At a recent TAPS (Australian Paphiopedilum Society) meeting, a guest speaker who is a specialty orchid fertilizer producer said that flushing with rainwater/RO/distilled water ‘ didn't work’ as well as a dilute fertilizer solution for removing ‘salts’.

This was met with some disbelief. No data was produced (or asked for). So I decided to do a little experiment.

I took 3 three healthy looking paphs. Plant A (laevigatum) in medium grade bark and a bit of CHC. No Aragonite. Plant B (Alex’s Spots) in bark/charcoal/CHC/perlite and a pinch of Aragonite per pot. Plant C (godefroyae) in a clear pot with good roots has about 5-10grams Aragonite in the mix. All repotted 6 months ago.

I hand water/flush Wednesday and Saturday over summer with collected rain water only (TDS 14, pH 6.4). Mist 4-8 times per day. I fertilize about an hour after the Saturday soaking. My usual fertilizer is Miracle Gro MaxFeed N20 P2 K9. I use half a teaspoon aiming for a TDS of 300 . I often add MgSO4 or Cal Mag or Cal Nitrate – but not in this experiment.
For the ‘dilute’ solution I used HSO 10 (a speciality orchid fertilizer) N10 P6 K25 at about 1/8th dilution (TDS 105, pH 5.8).
I used a ppm (TDS) meter and pH meter which I checked with 2 calibration solutions (pH 7 and pH 4).

Methods. I slowly poured through about 750mls of ‘solution’ through each pot and collected the effluent in a clean container. Measured the TDS and pH then sat the plant in the effluent and filled the container so the pot was 2/3 submerged for 15 mins. Re-measured. Repeated for each of rainwater, ‘dilute’ and ‘usual’ solutions.

Results – I could find no flushing effect with any solution – ie no change in effluent pH or TDS.

Discussion – The ‘dilute’ fertilizer flushing method doesn't seem to ‘extract’ extra salts as the input and output solutions appear unchanged at this level of measurement. It is possible that my current ‘flushing’ methods have already removed ‘excess’ salts so there is nothing to remove.

As an aside I think my paphs are much better with a rainwater usage as opposed to our tap water with a TDS of 250 and pH 6-7. (and K 'minimization')

I appreciate your comments on my little experiment.
Thanks

 

[Rick]

What is the pot size Ozpaph?

The amount of media relative to the amount (and time) for the water going through the mix is critical.

If the pot is say 2", with a max volume of 100 ml, and you pour 750 through it, then I would expect the results you are seeing. (same in same out). Also the amount of soak time is also pretty short (15 minutes). I my experiment the shortest time is 3 hours.

I would say that the differences in TDS are all within error. The pH changes are small, but probably meaningful.

But you could already see in the pots with aragonite a slight upward pH shift even with very short contact times. Even after 6 months of time in service.

If you extend the contact time by say pouring through multiple times or soaking longer, and still see these very small changes, then I would agree that you already flush your pots real good. These are very small changes compared to what I saw when I first started checking pot TDS. Water would go in with TDS 0 and come out 300. (maybe after 3-5 passes). I would also be putting about 100ml through a 4 in basket or pot. So lots more mix/water going through.

 

[Ozpaph]

Thanks Rick.
3" pots.
Ill do some repeat pour throughs on the weekend.

I chose a single pour through and 15min soak as these seemed 'real world'. I'm not sure how applicable a 3 hr soak or repeat pour throughs are but certainly worth doing.

 

[Rick]

The volume of a 3" pot (assuming close to cube) is about 450ml. So a simple pour through of 750ml would dilute any old water in the pot 1.7X. And that's assuming that it moves evenly past all particles in the pot. If it channels then it may hardly contact much of the potting mix at all.

You might try repeated soaks, with the filled volume.

 

[Stone]

At a recent TAPS (Australian Paphiopedilum Society) meeting, a guest speaker who is a specialty orchid fertilizer producer said that flushing with rainwater/RO/distilled water ‘ didn't work’ as well as a dilute fertilizer solution for removing ‘salts’.

He must have said something more? so far this statement sounds like crazy talk

 

[Ozpaph]

No. that's exactly what he said. He was ask to elaborate and said something about the new ions dragging out the old ones - to paraphrase. Many raised eye brows.

 

[DavidCampen]

At a recent TAPS (Australian Paphiopedilum Society) meeting, a guest speaker who is a specialty orchid fertilizer producer said that flushing with rainwater/RO/distilled water ‘ didn't work’ as well as a dilute fertilizer solution for removing ‘salts’.

This was met with some disbelief. No data was produced (or asked for). So I decided to do a little experiment.

He may have been thinking of the procedure of leaching CHC using calcium or magnesium ion to remove sodium ions that are bound to cation exchange sites on the CHC. If so then it is not applicable to extend this concept to flushing of pots that are in use since there isn't any sodium to be removed and the cations that are bound to the cation exchange sites of the medium are already in equilibrium with the cations in the fertilizer solution.

 

[SlipperKing]

That's one crazy fertilizer, HSO 10 with K25. Have you used this stuff on a regular bases? What kind of effects do you see?

 

[Rick]

He may have been thinking of the procedure of leaching CHC using calcium or magnesium ion to remove sodium ions that are bound to cation exchange sites on the CHC.

The organic media will hang on to K as well as Na. So after feeding heavily with a high K fert your mix will accumulate K (as most of us don't use a lot of sodium in our makeup feed).

I don't think you will get a good exchange of K by using a dilute version of the high K fert that put it into the mix in the first place. As David noted, you would need to use solutions with divalent cations in it to pull out monovalents.

 

[Ozpaph]

That's one crazy fertilizer, HSO 10 with K25. Have you used this stuff on a regular bases? What kind of effects do you see?

No, stopped it when I became a 'low K follower'.

 

[Ozpaph]

He may have been thinking of the procedure of leaching CHC using calcium or magnesium ion to remove sodium ions that are bound to cation exchange sites on the CHC. If so then it is not applicable to extend this concept to flushing of pots that are in use since there isn't any sodium to be removed and the cations that are bound to the cation exchange sites of the medium are already in equilibrium with the cations in the fertilizer solution.

He wasn't confused. He makes a product for pre-treating CHC - some sort of 'organic acid' solution. He talked about that separately.

 

[Stone]

He wasn't confused. He makes a product for pre-treating CHC - some sort of 'organic acid' solution. He talked about that separately.

Then he was taliking bullshit!

 

[cnycharles]

maybe his fertilizer regimens contain 'mystically energized' water particles that have been aligned with the bipolar continuum of the cosmos ( I believe there are filters available here and there with magnets in them, that accomplish this) :rollhappy:

also maybe they contain 'social ions'... that are so friendly, that when you put them into the pot and they flow out, the other extra fertilizer ions want to be friends with them and leave the pot with them (thus accomplishing leaching)

even better, the 'pied piper' flute that allows them to be musically removed from the media

 

[Stone]

maybe his fertilizer regimens contain 'mystically energized' water particles that have been aligned with the bipolar continuum of the cosmos ( I believe there are filters available here and there with magnets in them, that accomplish this) :rollhappy:

also maybe they contain 'social ions'... that are so friendly, that when you put them into the pot and they flow out, the other extra fertilizer ions want to be friends with them and leave the pot with them (thus accomplishing leaching)

even better, the 'pied piper' flute that allows them to be musically removed from the media

I want some of those! Where do I get them?

 

[cnycharles]

i'm sure I could find a flute for you somewhere, but it was somewhere on the internet where I actually saw some kinds of filters that were claiming to make water particles 'more alive', but don't remember what they were called (maybe someone here had a link and was asking about them)

actually I think beer has 'social ions' in it