plant ph and mag Issues after switching to cobs

[Greengenes707]

yes agree with all you stated.


standard fertilizer NPK expresses phosphorus as P2O5 and potassium as K20


so if you want to compare NPK ratios it would be nice to stick to standard fertilizer conventions.

regardless as that's just "a convention" I have actually seen the ph creep up that the OP is talking about.

I always mean N, P2O5 and K2O when refering to NPK just because that is the standard in the US for packaging nutrients and I feel like I would be confusing people if I gave them true NPK. Giving them both seems to confuse people even more. I'm not disagreeing with your reasoning though.

When giving ratios, I always put the : between the values (like you) because NPK rating is percent by mass, but most people don't understand this distinction anyway.

Honestly if we were talking about available NPK, it would make more sense if the standard was NO3-, KH2PO4-, K+ since those are the most available ions. Too bad the standards don't make much sense, especially for hydro users.

But standard nutrient science breaks down into actual NPK in ppm or mmol.
I talk with a few university greenhouse guys still from the AT days. As well as all my text research...it's all actual NPK. Even old threads from cap's or jack. Or even the basics of lucas being 1:1:2 is it's actual npk.

Some examples...
http://www.greenhouse.cornell.edu/crops/factsheets/hydroponic-recipes.pdf
https://edis.ifas.ufl.edu/pdffiles/CV/CV21600.pdf

I am in the camp of providing enough Ca and Mg regardless of ratio if it's 3:1 up to 1:1. Plants have constantly shown signs of Mg for me, but not Ca, as long as I'm in the 105ppm+ of Ca. While Mg needs don't settle till ~80 to up to 95ppm of Mg with the same ~120 Ca.
I have been testing a high P mix the last few runs and it has been really good. Ups the Ca too though, so my ratio got bigger...interesting. I have ran with no epsom at all(~60ppm Mg and got deficiencies once plants got to a decent teen size.



And last note...I am in coco, my Ca and other cation needs get increased with slightly.

 

[churchhaze]

Plants have constantly shown signs of Mg for me, but not Ca, as long as I'm in the 105ppm+ of Ca.

That's honestly why I was lowering my Ca. I kept seeing what looked like Mg deficiency and figured I had too much Ca. I also have very hard tap so I lowered Ca in hopes of freeing up Mg until I got (I think) calcium deficiency.

Maybe I do need to get my Mg levels up rather than Ca levels down. (hard to really experiment with only 2 flowering tents while wanting the best results)

Mix 21 (too little calcium nitrate). Pretty sure the plant was uptaking more negative charge than positive and thus pulling the pH higher quickly.

 

[churchhaze]

Increased ammonium like @PurpleBuz was suggesting should also help slow the rise of pH for the same reason. (at least theoretically) It means more of the N is absorbed as cations.

 

[OLD MOTHER SATIVA]

i am using npk [flowering nutes]with low Nitrogen
then cacium nitrate and magnesium nitrate also and bloong with silicon nitrate
itis working well i veg and bloom..ithinkifiballayhav e an actual one part formula
my plants have never been happier

 

[lukio]

Hey @Greengenes707 hows things dude! 1 light 1 plant is lookin beast!


Quick Q! - been struggling to get my head around salts...been a canna coco a+b guy for a while...

picked up some of this, no jacks in the UK. its called solufeed H. meant for hydro and tomatoes n things


Picked up some cal nitrate too, the plants look ok - ish... but was wondering if this looks good for canna too? I asked in the newbs section and in my thread but no real answers.

seems to kinda match up with what you suggest. think i might up the cal..

Soz about just dropping my question here!

cheers

 

[mcnasty_nug]

thanks guys for the replies. Purplebuz thank you, you're way over my head there. I get what youre saying though. Lower my P, add ammonium nitrate instead of diammonium phosphate.

So I did foliar some mag the other day, went a little too heavy i think thats what that glossy stuff on the leafs were. For now Im going to see if the fresh nute mix does anything. There is plenty mag in there.

my lights are maxed height in the tent. This was nagging in the back of my mind that the lights are just too bright. The only lux meter I have is the app on my phone and thats saying 65klux @ about 12". It said 30k lux under my 1kw lights at about 12. and 45k under 2x 315cmh. I do intend to get a par meter soon so i can try and play with the light coverage. Again Im going to give them a few days wit hthe new nute mix if that doesnt work I'll dim the lights. I think im about 24-30" off the canopy, the lights are off now I'll measure when they come back on.

setting the air back on the timer seems to have helped. My ph was only 6.02 when I checked it just now about 18 hours after i ph to 6.8 so thats a major win.

Im using ogbiowar root pack in the rez and pondzyme. I started using it after seeing what it did to the roots in my cloner, I've never seen so many roots on a cut before.


I pulled the buckets up to check the roots. the buckets were PACKED, the titan flow and grow leaves a bit of water in the bottom. It was so packed I feel the air wasnt getting in there well, there WAS a bit of brownish brittle roots along the bottom of the container. (i let them veg too long for these buckets unfortunately, im still learning this system and getting my timing right for the canopy) I chopped the weak roots out, and ensured the air lines are well within the water as some had gotten pulled up higher.

We'll see how it goes. I kinda hate the idea that the lights too bright. Good thing im building the basement into a room so I guess ill just cover more area with them if thats the case. The tents are bound to be relegated to veg rooms then,

 

[Greengenes707]

Hey @Greengenes707 hows things dude! 1 light 1 plant is lookin beast!


Quick Q! - been struggling to get my head around salts...been a canna coco a+b guy for a while...

picked up some of this, no jacks in the UK. its called solufeed H. meant for hydro and tomatoes n things
View attachment 4043882

Picked up some cal nitrate too, the plants look ok - ish... but was wondering if this looks good for canna too? I asked in the newbs section and in my thread but no real answers.

seems to kinda match up with what you suggest. think i might up the cal..

Soz about just dropping my question here!

cheers

Hey man,

You can work with it, but it might not be the best for replicating canna.

Here is canna coco with and without the PK boost...


I can not really replicate canna with it. Either veg or flowing canna.
You can replicate(I say this loosely) the canna w/PK with it if you also get some MPK


But can make some good basic ratio feeds with it, but all will be lower on in P than other mixes if you play around on the calculator with it. I have a video series planned for nutrients and all the calcs, just need my space back from my remodel. But if you get some MKP, you can make about anything you want.

Here is something close to jacks and what I run with your stuff...


And here is the same with a little MKP in the mix...

 

[lukio]

Hey man,

You can work with it, but it might not be the best for replicating canna.

Here is canna coco with and without the PK boost...
View attachment 4043950

I can not really replicate canna with it. Either veg or flowing canna.
You can replicate(I say this loosely) the canna w/PK with it if you also get some MPK
View attachment 4043956

But can make some good basic ratio feeds with it, but all will be lower on in P than other mixes if you play around on the calculator with it. I have a video series planned for nutrients and all the calcs, just need my space back from my remodel. But if you get some MKP, you can make about anything you want.

Here is something close to jacks and what I run with your stuff...
View attachment 4043959

And here is the same with a little MKP in the mix...
View attachment 4043960

nice one - thanks!

So, 2.4g per Gallon of the Solufeed should cover all my needs, right?

looking forward to the nute series, dude. hope the remodel goes well

 

[churchhaze]

A 2:1 Ca to Mg ratio is what I aim for and never have mag problems. Also for someone wanting to add Ca without adding a lot of N, Calcium chloride is an excellent tool to have in the arsenal. It also adds chloride, which is a micronutrient most people never think of and that a lot of gardens are probably a bit deficient in.

I personally cannot understand the obsession with everyone on RIU trying to get Ca without N. (and thus avoiding calcium nitrate) If you need more Ca, you probably also need more NO3-, and if you don't, you probably have too much KNO3. Likewise, if you need more N, chances are you also need more Ca.

Chlorine at the levels calcium chloride provides would certainly antagonize nitrates and phosphates. Chlorine is a trace element which is only needed at a very low concentration.

Calcium nitrate is the answer. Don't resist! If you're hydro, 100% of your calcium should be from calcium nitrate. (plants LOVE nitrates.)

 

[DrBlaze]

I pulled the buckets up to check the roots. the buckets were PACKED, the titan flow and grow leaves a bit of water in the bottom. It was so packed I feel the air wasnt getting in there well, there WAS a bit of brownish brittle roots along the bottom of the container. (i let them veg too long for these buckets unfortunately, im still learning this system and getting my timing right for the canopy) I chopped the weak roots out, and ensured the air lines are well within the water as some had gotten pulled up higher.

This my actually be your only problem. If your buckets are too small and become crammed with roots, a lot of that mass is getting drowned, not getting enough oxygen. I grow big plants in hydro (1 per m2), I only veg for 3 weeks or so in 5g buckets as they are too small, I need to switch to bigger buckets after that. In flower each plant has its own black/yellow tote (the one people use for reservoirs). You can get leaf die-off and what look like deficiencies when your buckets become crammed. You'll either have to flower earlier or get bigger buckets..

 

[DrBlaze]

I personally cannot understand the obsession with everyone on RIU trying to get Ca without N. (and thus avoiding calcium nitrate) If you need more Ca, you probably also need more NO3-, and if you don't, you probably have too much KNO3. Likewise, if you need more N, chances are you also need more Ca.

Chlorine at the levels calcium chloride provides would certainly antagonize nitrates and phosphates. Chlorine is a trace element which is only needed at a very low concentration.

Calcium nitrate is the answer. Don't resist! If you're hydro, 100% of your calcium should be from calcium nitrate. (plants LOVE nitrates.)

That's fine for your system. A lot of my nitrates come from my 120 gallons of fish tanks. All that water eventually ends up in my hydro system, and I have more than enough nitrates (fan leaves bigger than my face). All my Calcium comes from Calcium chloride, I've been using it for several years now with no issues. Calcium nitrate may be the answer for you but it would totally fuck up my nutrient recipe.

 

[HydroRed]

If this should be in the sick plant forum im sorry, I thought this would be more apt since this seems to be an LED related issue.

Short story, since i switched to cobs my PH rises crazy fast and Im seeing classic magnesium issues

Long story:
I recently build some LED lights out of Luminus cxm-22 cobs. Im running 2x lights in a 4x8 tent. Each light is 10 cobs mounted in a xxxl hood running at about 72w each. So Im looking at 1440w per 4x8. They are 3000k and a 50/50 mix of 80 and 90 cri.

My plants are in titan flow and grow system, Ive run this system before, and i have another 4x8 right next to this one that is still 1khps and all is fine. I had another 4x4 with one of these lights in it, i had the same issue. One of my drivers died so I have 2x 315 CMH in there now and the mag and ph issue is gone. (the 4x4 is a flood and drain table)

I use jacks hydro and calnit with some added microbes and geolite/rocks as my medium.
my room temp is 80-84 with lights on, my leaf surface temp is 76-79.

Ever since I moved to cobs, this tents rez PH is rising rapidly. IE I PH it down to 5.6 with botanicare phosphuric acid ph down and by the evening im at 6.5+

I am also seeing classic magnesium def signs.

Ive washed out my rez, I dont see signs of algea or anything crazy going on in the root zone, although my plants have filled up the buckets with roots, could it be root bound?

I just recently saw on PLC site that mag should be in the 75-90ppm range, my jacks is sitting at like 25-30ppm so i JUST started running my nutes as such:
jacks 3g
cal-nit 2.5g
mag sulfate 2g
diammonium phosphate .25g (i read the ammonium base helps buffer PH lower, doesnt seem to be working tho)
growsil .25g

This has my mag at 75ppm exactly I'm pretty sure.

so, any ideas whats going on here? Like I said I have several other tents going with HPS, CMH, and even a veg area with citizen 6500k cobs and none of them are giving me these issues. Its JUST the cob tents.

I noticed Mg deficiency as well whenever I used my led light on other grows throughout flower. I dont have to supplement when I run the same strain under my hps.
I recently introduced my led light into my momma room and in under a week started showing deficiency. Cant say I've ever noticed any affects on my pH though.

 

[captainmorgan]

I remember @captainmorgan having PH rising issues at one time, not sure what he did. I know veg bloom has that issue in RO sometimes without the right buffer too.

Hey GG how's it going, the veg+bloom is very stable with just cal mag added but my rising PH issues were from mixing in another product from another company. Seems to have been some interaction between the two products and it corrected itself when I eliminated using that product, can't think of what it was but maybe I posted it back then.

 

[sethimus]

Hey @Greengenes707 hows things dude! 1 light 1 plant is lookin beast!


Quick Q! - been struggling to get my head around salts...been a canna coco a+b guy for a while...

picked up some of this, no jacks in the UK. its called solufeed H. meant for hydro and tomatoes n things
View attachment 4043882

Picked up some cal nitrate too, the plants look ok - ish... but was wondering if this looks good for canna too? I asked in the newbs section and in my thread but no real answers.

seems to kinda match up with what you suggest. think i might up the cal..

Soz about just dropping my question here!

cheers

try yara brown, or hakaphos base 4 or universol white as a base nutrient, they are all similar to jacks

 

[lukio]

try yara brown, or hakaphos base 4 or universol white as a base nutrient, they are all similar to jacks

thanks dude! i'll have a look this eve

 

[mcnasty_nug]

This my actually be your only problem. If your buckets are too small and become crammed with roots, a lot of that mass is getting drowned, not getting enough oxygen. I grow big plants in hydro (1 per m2), I only veg for 3 weeks or so in 5g buckets as they are too small, I need to switch to bigger buckets after that. In flower each plant has its own black/yellow tote (the one people use for reservoirs). You can get leaf die-off and what look like deficiencies when your buckets become crammed. You'll either have to flower earlier or get bigger buckets..

I think it certainly is a major issue. i vegged for 5 weeks. Definately too long for these buckets. Its a shame since I can get these systems for absurdly cheap, but I might have to just stick with tables for the rest of my flowering rooms as I really dont want to be running so many plants. I chopped the roots back some, i hope that doesnt stress the plants way too much. Im on day 3 of flower so, I dont think it will be THAT detrimental.

It seems like the air in the rez was the PH issue. I phed to 5.8ish last night and this morning its 5.82. I had one of those pondmaster ap-40s on two 50g rez. chaning it back to 15 on per hour seems to have fixed that issue.

As for the plants. Its too early to really tell but they seem to be starting to green up. I will keep everyone posted anyway in case someone else has these problems.


Greengenes I have to say its an honour to have you hit my thread! You (and mou5) videos taught me pretty much everything I know about building leds. Dieing for a tech talk!

Thanks everyone for your help!

 

[mcnasty_nug]

I noticed Mg deficiency as well whenever I used my led light on other grows throughout flower. I dont have to supplement when I run the same strain under my hps.
I recently introduced my led light into my momma room and in under a week started showing deficiency. Cant say I've ever noticed any affects on my pH though.

If this continues to be a thing, I might have to mix CMH in the room or something and see if that helps.

 

[captainmorgan]

If you have no issues with PH or temp and the plant wants more of something it's a good sign of increased growth or development not a negative.
You should already be adjusting your feed between different strains so just think along those terms.

 

[lukio]

Just re-read that way less stoned and it made a lot more sense! cheers. Sorry for the hijack @mcnasty_nug ! hope you solve the issues

cheers

 

[mcnasty_nug]

final update. It seems the problem is solved. Getting my PH under control by lowering the times the air went on, and bumping up the mag to the doses I posted earlier has solved it. Plants leaves are all nice and green again. Thanks again to everyone who took the time to help me out. Much appreciated.