Mid flowering - K def?

[Delty]

thanks for your help!

I didn’t actually get a chance to test the run off EC! I have flushed it through with canna flush and rewatered through at 0.8EC total, 0.15EC of which is calmag the rest just a+b. Presuming a little cal mag is needed given im using rain water and the coco is over 11 weeks old so will have broken down somewhat?

 

[Del boy]

thanks for your help!

I didn’t actually get a chance to test the run off EC! I have flushed it through with canna flush and rewatered through at 0.8EC total, 0.15EC of which is calmag the rest just a+b. Presuming a little cal mag is needed given im using rain water and the coco is over 11 weeks old so will have broken down somewhat?

Did you test the ph and EC of the run off after flush?? and did you flush the canna flush with plan water after you done it before you fed them again?

 

[MIAutomatic]

thanks for your help!

I didn’t actually get a chance to test the run off EC! I have flushed it through with canna flush and rewatered through at 0.8EC total, 0.15EC of which is calmag the rest just a+b. Presuming a little cal mag is needed given im using rain water and the coco is over 11 weeks old so will have broken down somewhat?

It sounds like you are on the right track, keep the EC low and the PH balanced and I think your plants will recover. An issue like this usually takes several days/waterings to fully resolve.

Here is what is going on when you are rinsing your coco with lower strength and calmag buffered nutrients:

Coco has a high cation exchange capacity, which means it has lots of ion sites that will bind to things like Calcium and Magnesium. Most bagged coco like Canna, is fully pre buffered with calmag and can get by without any added for quite a while since A & B also contains some calmag. As the roots work their way through the coco new cation sites are exposed and they need to be bonded with something. Coco likes to bind with calcium and magnesium better than other molecules so it will prioritize them, and if the calmag dose available is already low then it will use up everything leaving nothing for the plant. If there is not enough calmag to bind to the cation sites then the macro nutrients are next in line. When more calmag becomes available the cation sites will drop the NPK it has bonded in favor of the calmag thus releasing the NPK into your runoff and raising the EC significantly from the inflow. Once a new cation site is bonded to calmag is will remain that way so as root growth slows the coco will start to use up less calmag. As plants move into flowering they will begin to use more calmag but since the coco is no longer binding so much of it to cation sites the net need for calmag drops and you can start to reduce the amount added for the remainder of the grow cycle. After flower stacking is finished I will back off to only .2 EC calmag and continue with that for the remainder of the grow.

I hope this is helpful, I put it all down to help further my own understanding as much as anything else. All of this was gleaned from reading articles on Canna’s website and cocoforcannabis.com.

good luck!

 

[Delty]

I did not tear after the flush itself but did put over 3x pot volume through it steadily over the course of 20 mins or so. I then fertigated with 1x pot volume. EC is 0.8 going in and about 0.74 on the run off - does this suggest the CESs are not fully saturated yet?

 

[MIAutomatic]

I did not tear after the flush itself but did put over 3x pot volume through it steadily over the course of 20 mins or so. I then fertigated with 1x pot volume. EC is 0.8 going in and about 0.74 on the run off - does this suggest the CESs are not fully saturated yet?

That sounds good to me, as long as your runoff EC is within a few points of your inflow then things generally stay looking good. Are you using zyme and rhizo? I know a lot of people skip them but I use the whole lineup.

 

[Delty]

Yes using both of those too. I also have Boost to hand but only tend to use it when everything else looks good. If this fixes the issue I’ll introduce it. Thanks again

 

[Delty]

So 3 days after the flush and feeding to 0.8EC (.6 a+b and .2 calmag) and the issue is still progressing at the same rate.

any ideas for a last ditch attempt to save before the there’s no photosynthetic capable leaves left?

 

[durbanpoisoner]

I agree with my fellows here. Often what you think is a deficiency is actually a lockout by providing too much of key nutrient. I really don’t see too much of a need to feed over 1.2-1.3ec. I would back off the pk booster and instead up the calmag a bit and keep the EC in that range.

I ran 10ml/gal calmag along with the canna ab nutes in coco. Less is more. Don’t love your plants to death.

 

[Delty]

Thanks will definitely be very tentative with EC on next grow cycle, but I’ve now flushed the plants fully and have been feeding a reduced feed at 0.8-0.9EC (0.2 calmag, rest a and b) and the problem is persisting and the leaves are rusting at the same rate.