Photoperiod K Deficiency???

[Builder0101]

Thanks again for all the support. I found this publication from 2019 that covers humic acid supplementation.

Impact of N, P, K, and Humic Acid Supplementation on the Chemical Profile of Medical Cannabis (Cannabis sativa L)

Mineral nutrition is a major factor affecting plant growth and function. Increasing evidence supports the involvement of macro and micronutrients in secondary metabolism. The use of the appropriate nutritional measures including organic fertilizers, supplements, and biostimulants is therefore a...

www.frontiersin.org

Interestingly, the authors found that humic acid supplementation actually reduced THC and CBD at the top of the plants. From the paper:

“HA was found to reduce the natural spatial variability of all of the cannabinoids studied. However, the increased uniformity came at the expense of the higher levels of cannabinoids at the top of the plants, THC and CBD were reduced by 37 and 39%, respectively. Changes in mineral composition were observed in specific areas of the plants”.
There is still so much to learn!

Yes that is interesting. Since we all try to coast to the finish and humic is intended to assist in vigorous growth, consider discontinuing its use for last few weeks of flower. Just thoughts.

 

[Kinezokyprios]

Yes but it is something to promote green growth/health anyhow (size of buds included along with leaves) and not something that you would use more than once or twice. You must not stop your regular feed schedule. And I suggest you to use a bloom booster that has no or low NPK. A nice combination would be biobizz top max along with GHE BioBud (or any other name they use for marketing, like TA Bloom Booster). Works well and the kelp extracts, aminoacids and hormones they contain will really help in flowering and potency.

 

[Builder0101]

Yes but it is something to promote green growth/health anyhow (size of buds included along with leaves) and not something that you would use more than once or twice. You must not stop your regular feed schedule. And I suggest you to use a bloom booster that has no or low NPK. A nice combination would be biobizz top max along with GHE BioBud (or any other name they use for marketing, like TA Bloom Booster). Works well and the kelp extracts, aminoacids and hormones they contain will really help in flowering and potency.

Been thinking about using an organic liquid bloom as I move towards finish. My thinking was the liquid will deplete more quickly and I dont want a bunch of NPK in my medium at the end. Have not considered zero NPK bloom. Thank you. I will research it. Can you clarify which ones are zero NPK.

 

[BII]

Thanks @Builder0101 and @Kinezokyprios! Appreciate the guidance. I shut off the blumats for a few days then doused a tea of earthworm casings, molasses, kelp meal and tiny little shot of fish emulsion (holy crap that stuff stinks!). No real change, but it’s been only a few days. I understand unsulphured blackstrap molasses is a chelator as well as a good source of K (1:1:5 or so I’ve read) so I was planning on keeping that going in all subsequent waterings. Little hesitant to do any foliar at this point given I’m in week 6 of flower so are you suggesting a very targeted foliar on just the yellowing leaves? Also any ranges And application suggestions for the amounts of humic and fulvic acid? I did add a little humic acid in the original super soil mix but it was only 1 tsp for 40 gallons so...?

Another thought I had on this yellowing thing was simple overwatering from my blumats. It didn’t seem like the soil was overwhelming wet and I didn’t experience any flooding, however I was steadily increasing the water drip during weeks 2-4 of flower and was going through a solid 2 gallons a day before I went into infirmary mode snfnshut it off. Don’t know if that’s a cause however it’s another possibility in the realm of reason I suppose.

Re: the dehuey condensate, I went back and forth on that one so I totally understand your comment. However given the ultra low ppm and the fact that my dehuey is only about 4 months old, I’m not overly concerned about pathogens at this point. Read a number of articles and forum posts on this and it seems like another one of those topics where anectodal stories and strong opinions drive people’s decisions. Would love to see a research paper or other peer-reviewed study that detailed the pathogens that could be found in condensates and the risks associated with them. I’m generating 5 gallons every 3 days and it’s a shame to not utilize such a low ppm water source.

Regarding microbial contamination concerns wtih dehumidifier condensate, this at worst contains what's in the air (with these cells and spores coming mostly from soil). So I don't think dehumidifier concentrate will harm plants or soil microbes. But you can always 'sterilize' the water with a proper dose of bleach (and let stand/vent for a day) or H2O2.

 

[Kinezokyprios]

Been thinking about using an organic liquid bloom as I move towards finish. My thinking was the liquid will deplete more quickly and I dont want a bunch of NPK in my medium at the end. Have not considered zero NPK bloom. Thank you. I will research it. Can you clarify which ones are zero NPK.

Since they are organic and contain organic matter a bit of NPK is unavoidable, but low volumes of 1-1-1 or 0--01 or similar are ok. Since they are not in the range of 9-15 or 12-14 it is clear they work on another level that really promotes microbial, fungal and therefore the plant's life itself. You can replace a homemade tea that might fail or might be too nutritious with them or work along this and of course your standard fertilizer. I believe that you agree that the point is to increase the plant's appetite and make it eat what little we provide and not to force feed it. Well if the plant itself asks for more food you can always add, but not on your own initiative.

 

[beachbuds]

Made the decision that I need to supplement with chemical salts to finish the run as the leaf loss and yellowing/burning symptom was accelerating. Brought some tiger bloom back into the mix, cal/mag 4:1 supplement, molasses, and pH adjusted to 6.5 using pH up, which is apparently potassium carbonate so additional K there too. My 3x3 tent with 4 clones of the same strain has absolutely zero K issues. It does have double the amount of soil per sq ft of canopy though: 20gal for 9sq ft compared to 15 gal for 16sq ft. Now understanding the value of multiple containers compared to a single. I think my next run in the 4x4 will have 4x7 or 4x10 gal if they will fit. Plus I’m gonna cook the soil longer. This first batch only cooked 3weeks and some of those nights it was pretty cold outside. Might be that the majority of the K and P of the super soil from bone and blood meal respectively were just not ready yet. All just more data to learn from I guess.

Condensate from the dehuey is a no brainer for me, agreed.

 

[Waira]

- K defc most likely,... any other supplements going with K in it? I ask because K toxicity looks pretty much the same, tip and margin "teeth" burn,... Purple petioles aren't a sign of K defc., P occasionally, but more often it's normal color expression, not a solid diagnostic tool by itself...
Have to checked the in-pot pH yet? No matter what the soil and/or feed regime is, off pH and happen... Any teas/inoculants going in? Molasses does have some K, but is it enough in actual quantity, not ratio is the question,... likely not. You need to get that pH measured with a good quality pH probe, run-off is useless especially in that type of soil. K doesn't lock out easily, so probably you're OK or borderline there, but the catch-22 is if it is off, tinkering with feeds may make matters worse, not better! The Accurate 8 (CWP) is a nice unit, mine serves me well for years now....
What do you have on hand for a K source? BTW, don't take leaves off like that , it fixes nothing and in fact makes things worse when it's a mobile (within the plant) nutrient involved; they are storage for such nutes, and can be translocated to needed growth when supply is short,..
In the future, I'd avoid soils, particularly OF; it's the #1 problem soil I see in here, often badly off pH right out of the bag, full of garbage bits, poorly cooked, bugs a common complaint as well,.. it very hit&miss with them, some get OK bags, others get shwag!
Check out the reference section in here, some good articles on things like humic-fulvic, VPD, etc.,...

 

[beachbuds]

Thank you @Waira. I have checked soil pH with Apera pH20 at multiple depths in the big pot using 1:1 slurry of soil and RO water. Results range 6.8-7.0 so lockout prob not the issue. I really was trying to do the super soil water only thing until this problem showed up so I literally just went back to the bottle yesterday. Only feeds/supplements prior to yesterday was 2 compost teas with molasses and EWC at week 2 and week 4. The kicker on this grow is the clones in the other tent, in the same super soil batch, are looking flawless using the water only regimen and just those 2 teas (1st pic in the set). Temps and RH basically identical as they are in the same garage. 2 Autocobs and a spider farmer sf1000 full spectrum light power that tent. Petioles are slightly purple but not nearly as deep as the big plant. Having these reference plants has been so helpful to compare against. The soil volume:sq ft canopy theory is what leads me to believe it’s a true deficiency with my big mama. Lesson learned on the OF. Don’t know what the base soil levels of K are in OF, however the sub cool super soil recipe calls for a coco base soil, Roots I believe it is. Roots has a lot of K sources Right on the bag plus coco apparently releases K as it decomposes. OF being peat based doesn’t seem to have these sources included so it really looks like it was just a rookie substitution on my part. I couldn’t source Roots locally and don’t want to have Amazon deliver me dirt so I went with what I had not fully understanding the problem I was creating. Love and learn.

Pics below were from today and I already think she’s looking better from just 24 hrs after a shot of tiger bloom and more molasses. Agree on minimizing the leaf removal, makes perfect sense about not taking away nute stores. Was removing partly to allow the lower leaves to see more light. Since the chlorosis was pretty advanced on some leaves, I was assuming they were less effective at photosynthesis and by removing them I could allow healthier/greener leaves to see more light. I was pretty strategic about it in the upper parts of the canopy. Hopeful that getting some K back in her now will halt the damage and I can ride out the next 3-4 weeks and still pull a decent harvest.

BTW, this forum is great, everyone continues to be so helpful and supportive. Great ideas and nice dialogue with no BS one liner answers or attitude. Refreshing for those of us interested in learning the science, theory and skills of cultivating quality cannabis. Rock on autoower.net community!

 

[Waira]

The kicker on this grow is the clones in the other tent, in the same super soil batch, are looking flawless using the water only regimen and just those 2 teas (1st pic in the set)

Different strain, genetics, tolerances, demands, plus each pot is it's own little ecosystem; they may start the same, but sure don't stay that way!
Yes on the nutes ASAP! I suspect a micronute defc.(s) may be kicking off too, from the looks of those faded top level fans.... Kelp or a mineral supplement will help with that, Earth Juice Microblast is my fav',... Broad coverage, sulfate based mainly so the S boost is welcome too!
Did you say how far away the lights are? Dig your choices there, AutoCOB's and SF1000 - I'm looking to snag on of those myself, I am sold on Q-boards... I like the limited shadow casting they offer.. AutoCOB's I like the point and height adjustment flexibility with them...

Yeah, give a few days or so for things to get in there and working,.. damage won't be fixed; only some, if any color will improve much, it's halting of progression you're looking for,...plus the fact that some fan fade is normal now too, lowers first and worst... Buds look good so let's see what several days brings -

BTW, this forum is great, everyone continues to be so helpful and supportive. Great ideas and nice dialogue with no BS one liner answers or attitude. Refreshing for those of us interested in learning the science, theory and skills of cultivating quality cannabis. Rock on autoower.net community!

Cheers to that! It's nearly all volunteers here that man the shop... it's our duty to keep the Vibe like it is, and has been signature AFN from day one... No-Troll Zone! .... Here in Sick Bay especially, kicking peeps when they are down, new and learning the hard way is 100% dick-move behavior, and gets quashed hard and fast -

 

[Tom Bombadil]

hmmmmmmmmmmmm
appears as though the super soil pooped out early, or didnt sit long enough, or with too little moisture during the 30 day minimum "cooking" process?

did you layer or mix it in? looks hungry overall...
plant should be more green..
mammoth p or recharge may help a bit..
humic acid powder takes a long time to break down
top dressing with a couple more inches of super soil wouldnt hurt, if u have extra
gl