I'm growing a few plants on a mix of peat moss, perlite and vermiculite, and I'm having some very strange problems with the run-off pH. In order to raise the pH of the mix — it was getting dangerously acidic, reaching as low as 4.8 — I've been flushing the plants until the run-off registers a very low ppm and the pH is somewhere around 6-7, and just as all the excess water runs off I immediately feed them a solution with a pH between 6.4-6.6, in the hopes that it'll maintain this level until the next watering/feeding.
However, even though the last drips of water that runs off after the flush registers a pH of around 6-7, as soon as I start adding the fertilizer (again, with a pH between 6.4-6.6), the run-off starts trending lower and lower. I usually prepare enough solution to match the pot volume, and even after this second "flush" with pH'd nutrients, the last run-off ends up registering a pH of around 5.0, sometimes even lower.
I have no idea what is happening. The pH meter is fine and is regularly calibrated, and I also double check everything with pH strips just in case. I'm using a sodium hydroxide (NaOH) solution to increase the pH, and before that I was using a sodium bicarbonate (baking soda, NaHCO3) solution, but that wasn't working too well and I always ended up with a solution with way too much sodium in it. With the new solution, I'm registering a 50-80 ppm increase in total dissolved solids to bring my most acidic solutions up to the recommended levels. Can someone chime in on what may be happening?
However, even though the last drips of water that runs off after the flush registers a pH of around 6-7, as soon as I start adding the fertilizer (again, with a pH between 6.4-6.6), the run-off starts trending lower and lower. I usually prepare enough solution to match the pot volume, and even after this second "flush" with pH'd nutrients, the last run-off ends up registering a pH of around 5.0, sometimes even lower.
I have no idea what is happening. The pH meter is fine and is regularly calibrated, and I also double check everything with pH strips just in case. I'm using a sodium hydroxide (NaOH) solution to increase the pH, and before that I was using a sodium bicarbonate (baking soda, NaHCO3) solution, but that wasn't working too well and I always ended up with a solution with way too much sodium in it. With the new solution, I'm registering a 50-80 ppm increase in total dissolved solids to bring my most acidic solutions up to the recommended levels. Can someone chime in on what may be happening?
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