Autoflower soil Low PH Runoff with high ppm

Soil PH range is 6.3-6.8 with 6.5 being the sweet spot Growmie. A good soil PPM range would be 1000-1200ish. I would feed next time at a PH of 7.0 and 1000 PPMs and test the run off. What nutrient brand are you using? The soil PH usually gets that low from an accumulation of salt build up, this will drive up the PPMs and tank the PH. Liberal run off on feed or water days helps prevent this :love_you_gesture:

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This^^ once the salt buildup is flushed, the ph should stabilize. If not, a tablespoon of gardening lime (not dolomite) will help stabilize.

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Thanks for the info…just had a thought though. I’m seeing that it might take 3-5 times water to flush a plant properly. I have 7- 5 gallon pots, and 1- 10 gallon pot. The TDS of my tap water is 250-280. So if I’m adding that much tap water to flush aren’t my plants going to get too many nutes and the problem won’t get fixed. If the solution is distilled water then it’s going to cost a fortune!!!

No, as the name suggests, flushing will wash that away.

Distilled water wont work for flushing. Flush water must be ph stable (250-350ppm tds) and set to 6.8ph. After your flush you will need to reapply nutrients. This should all be done in a single session. You will flush until the runoff comes back into range then allow excess water to drip (takes 10-15 mins) then immediatly mix up a feed and apply it. This will need be done slowly. There will be lots of runoff. Its amazing though as you input at 1200tds and only 5-600tds comes back out.

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So you’re a genius! Got my tds readings to about 800 and let it all drain out and then fed nutes slowly(1500 Tds) and the runoff tds was 500! Yay! It does take a long time to flush though!!! I’ll try to make sure that doesn’t happen again. Thanks for the help.

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Anytime, and you are most welcome.

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Similar problem here… i set up initially running organic pots but ended up switching a few weeks back to address difficulties. Im guessing the high run off ppm is due to that (residual organics)? Will a flush be possible with organics in soil?

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Im guessing by switched you mean you input synthetic nutrients of some kind? If thats the case that would be why you have a high ppm runoff. What exactly was your runoff ph and tds?

Do you mean to reset soil ph or a final flush where as no more nutes are supplied in the final cple weeks of flower?

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Yes correct, synthetic. Run off ph was 5.2, ph in was 6.2, ppm in 1065…ppm out over2000

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Assuming you are in soil only give ph stable water (350ppm tds), ph’d to 6.8 at each watering until your runoff tds drops below 1000ppm. Then, on the next input, feed.

Its very important that your water input is ph stable. What kind of water are you using?

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Thx doc… my water is from a water tank. I had 3, 3gal pot to do, it took a bit… but i think i got there, (1st time ever flushed). Water just over 6.8 and ppm just over 360


Got the outs under 800ppm and ph up to 6.4 from 5.2. Waiting to see how they respond. Are you saying i should be more consistent with the 6.8ph at water and feeding? I’ve been trying 6.1-6.3, but see on my feed chart, is 6.2-6.8… imma adjust to the higher and monitor, thx doc

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Yes. When deciding what ph for my next input I use my previous runoff as a guide. If my last runoff was below 6.5 then I ph my next input at 6.8. If my last runoff was above 6.5 then my next input is at 6.5. Make sense?

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Gotcha… will make a mental note for this. Plants look happy this morning. Thanks

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Excellent! You are most welcome my friend.

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