Im always amazed when people talk about ppm @ 1200,1300.Day 26 from flip and the dreaded RDWC mid-flower pH plummet is starting to happen.
I'm mitigating the effect of the drop by using pH Perfect base nutes as the chelation means a wider pH range in which the nutes are available; i start to worry when i hit the 4s and change-out at 4.0 (although i've seen it hit 3.8 in past grows). This past week the pH started drifting down to 5.1 by Wednesday night and then plummeted by another 0.6 to 4.5 by end of ON cycle yesterday morning. My plants have been drinking about 7 gallons of top-up nutes per ON and they really like their CalMag. Yesterday though i took a chance after looking at what Aqua Man and BioMaster have said on the topic and added in more base nutes to both my system and the top-up. An hour later the system had gone from 1360 ppm @ 4.5 pH to 1460 ppm @ 4.8. The top-up got a stronger shot of base nutes and by end of ON cycle this morning nute strength was 1500 and pH is at 5.0. I'm due to change-out tomorrow so i just refilled top-up with RO water and strength should drop down a bit by tomorrow morning.
Tomorrow i'll change-out with lower strength nutes in order to leave headroom if i need to try and bump pH levels up and hopefully extend the time till change-out. I'm trying to keep RH in low 40s and my ON temps rise into the low 80s, with OFF temps low to mid 70s due to added heat from dehuey.
What source are you using for the Potassium bicarbonate, walked out to our grow after reading your post and the ph crash has started here. I'm on day 18 flower. Nutes were at 480 ppm yesterday and 5.8. Readings just now before adding anything were 410ppm and 4.7I've been hitting them pretty hard with Overdrive and potassium bicarbonate and feel that my ratios are probably way out of whack, so i did a change out today. Leaned a tad more on the B than the A, added in B52; Overdrive; Bud Factor X; SensiZym and HydroGuard, all at reduced doses. While i have a slick on the top of the epi there is no film on the float valve nor is there a smell so i believe it's bacteria die-off as opposed to root issues. Potassium bicarbonate has been working well for keeping pH relatively stable and i've stayed between 5.4 - 6.0 for the most part, aiming to keep solution strength between 400 and 500. Strength has gone to 550 and pH 6.0 right after adding potassium bicarbonate but it usually drops into the zone within a few hours.
We're having damp, hot weather and it's been difficult to keep temperatures under 80 during ON cycle, so terpenes are taking a hit. RH is running mid to high 40s and the dehumidifier is definitely contributing to the heat issue. No budget for a mini split so i'll likely try to find a way to use a 14 000 dual hose portable ia already own, next year. I need to find out if i can extend the ducting beyond 5' if i put inline fans on them to accommodate basement windows.
How was it used?Straight potassium bicarbonate powder, from Amazon, https://www.amazon.ca/Home-Brew-Ohio-Potassium-Bicarbonate/dp/B0064GZPU4/ref=sr_1_3?dchild=1&keywords=potassium+bicarbonate&qid=1622069993&sr=8-3
Many thanks to Aqua Man for turning me on to this fix.
You can see the K deficiency in the leaves in the foreground, while those in the background are further into their late flower fade as the plants ripen.
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