low ph in root zone during flowering, why?

[cottageman]

I am growing in plastic 9x9 inch pots with rockwool croutons for the medium. I am using Heavy16 products for the most part and my problem is occurring during the beginning of flowering. Temps in the room are maybe a degree or two higher than I want but it is still within healthy range. Everything is perfect in veg, no yellow at all and runoff ph and ppm's are exactly where they should be. By the second week of flower the runoff ph drops to 5.4 range and the plants start to yellow due to the low ph, why is this happening? I am pretty much following heavy16 recommendations, and I always go a bit lower than what the manufacturer recommends, do I just need to up my base a bit? I do not know what would make the ph fall rather quickly in those first few weeks. I will post pictures of the plants later but it looks like a mg deficiency which has to be caused by the low ph. What is causing this?

 

[Kevinkellog]

R u over watering? Generally when rockwools dry the ph goes up. But when u have a build up of nutrients from a line, the ph will fluctuate . I would recommend slowing on the mutes, adjust water in the 6 range . Then check runoff. Add nutes once ph is under control

 

[cottageman]

R u over watering? Generally when rockwools dry the ph goes up. But when u have a build up of nutrients from a line, the ph will fluctuate . I would recommend slowing on the mutes, adjust water in the 6 range . Then check runoff. Add nutes once ph is under control

I do not think I am overwatering because there is no droopiness on the plants just yellowing. I have already cut back on the nutes, I am watering just under 1000pppm(500 scale) during flowering and I feel like that is pretty low already. I think it has something to do with the cation exchange as I have heard that if it is not eating enough p or k the plant will lower the ph of the medium. I will see how wet they are today and I will check runoff today and let you know what it is at ppm range. Would letting them dry out and flushing with lower ppm's and some enzymes/ bacteria help me out?

 

[Dirtbag]

5.5 from what I understand is fine for hydro, but 2ec seems really high to me. I am not a hydro guy so take that with a grain of salt. But if the plant isnt uptaking some nutrients and you get salt buildup in the rockwool, that will lower ph. what does runoff ppm look like?

Other thing to check would be root health. Bad bacteria can lower ph pretty fast too.

 

[Kevinkellog]

A pic would be awesome. But yeah anything to break down any build ups of a mineral while deficient in others, I would throw in cannazym or similar. Then a humid acid to break down even more heavy metals in the medium. Diamond black is great stuff. Also make sure u r oxygenating ur water. Add 6.5 water get the medium neutral to 6 I also recommend . Flushing with cannas flushing solution. Includes enzymes that break down the salts

 

[cottageman]

5.5 from what I understand is fine for hydro, but 2ec seems really high to me. I am not a hydro guy so take that with a grain of salt. But if the plant isnt uptaking some nutrients and you get salt buildup in the rockwool, that will lower ph. what does runoff ppm look like?

Other thing to check would be root health. Bad bacteria can lower ph pretty fast too.

2 ec is pretty standard for hydro with co2, they’re feeding schedule says around 1300ppm lol and the ppm runoff seems fine, if anything it goes down the longer I go into flower which is why I’m confused

 

[cottageman]

A pic would be awesome. But yeah anything to break down any build ups of a mineral while deficient in others, I would throw in cannazym or similar. Then a humid acid to break down even more heavy metals in the medium. Diamond black is great stuff. Also make sure u r oxygenating ur water. Add 6.5 water get the medium neutral to 6 I also recommend . Flushing with cannas flushing solution. Includes enzymes that break down the salts

Yeah I use all of these for the most part already. I use enzyme complete which is awesome, heavy prime has humid and fulvic acid plus I throw in some biosis which is humid acid, kelp and molasses. I will do a flush today if they’re dry enough and see if it keeps the yellowing at bay. The yellowing is not bad right now but I know it’ll get a bit worse if I don’t try something

 

[cottageman]

A pic would be awesome. But yeah anything to break down any build ups of a mineral while deficient in others, I would throw in cannazym or similar. Then a humid acid to break down even more heavy metals in the medium. Diamond black is great stuff. Also make sure u r oxygenating ur water. Add 6.5 water get the medium neutral to 6 I also recommend . Flushing with cannas flushing solution. Includes enzymes that break down the salts

These are a few of the upper leaves on the table that is in the middle of week 2

 

[Dirtbag]

2 ec is pretty standard for hydro with co2, they’re feeding schedule says around 1300ppm lol and the ppm runoff seems fine, if anything it goes down the longer I go into flower which is why I’m confused

Didnt realize you were running Co2, how do your roots look?

 

[cottageman]

Didnt realize you were running Co2, how do your roots look?

They could be a little more white but pretty good. No brown or black tips for the most part and roots are coming out of the bottom and top of the pot

 

[Beachwalker]

I am pretty much following heavy16 recommendations

^ this

 

[cottageman]

Here’s what most of the plants look like on the table. It is very dry so it’s definitely not overwatered, and this yellowing seems to stop around week 4. I know it has to do with the low ph in my runoff I just don’t know what to do to fix it

 

[Kevinkellog]

Top feeing flood and drain or drip?

 

[cottageman]

Top feeing flood and drain or drip?

Top feeding and drain to waste. I flushed a plant on the table and runoff came out at 1400ppm(500 scale) at 5.5 ph so I am going to do a flush to bring up the ph and lower the ppm runoff a bit but the runoff doesn’t seem THAT bad to the point of all yellow in 2 weeks?

 

[Kevinkellog]

To me u may have been running way too high on the TDS. Lower ur nutes. Prolly the salt build up is why ph is down. Light on the nutes!

 

[Dirtbag]

Yeah those look overfed

 

[cottageman]

To me u may have been running way too high on the TDS. Lower ur nutes. Prolly the salt build up is why ph is down. Light on the nutes!

I flushed with 3/4 strength nutes and extra enzymes humic acid and bacteria. I was thinking that’s what it was but needed to make sure. Before heavy I was running 12-1300 ppm in flower and didn’t have this problem which is why I was so confused

 

[cottageman]

I flushed with 3/4 strength nutes and extra enzymes humic acid and bacteria. I was thinking that’s what it was but needed to make sure. Before heavy I was running 12-1300 ppm in flower and didn’t have this problem which is why I was so confused

my runoff yesterday was in the 1400 ppm range and 5.3. I just checked the runoff from the flush and it’s at 1250 at 5.6 so that definitely helped the ph! I will see if the yellow continues after or if it stalls and gets a bit better

 

[cottageman]

A quick update, you guys were absolutely right. The table that was yellowing by the day has stopped yellowing, and every plant is praying pretty hard now that I’ve gotten the ppm’s down. For reference here is the new flowering table with the same strains, at the beginning of week 2 when I first started this thread and they are looking pretty healthy! Thanks for the tips guys everything is looking a lot better