- Jan 15, 2011
- Reaction score
- Brisbane, Australia
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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.