Sour Crack in hot soil

[Sloth]

Hey all, this is my first post on here. I've been using the site for a year or so though so firstly, thanks to everyone that contributes - I've learnt so much from many of you on here and seeing some of the results is really pushing me to dial in this new setup and get some healthy plants and big yields.

Unfortunately, I've come across issues early on after adjusting my soil this run, so have come to ask some advice regarding my young plants which are showing signs of n toxicity.



Plants: 7 Mephisto Sour Cracks on day 16 from germination.
Light: HLG 260w LED Quantum board
Light schedule: 24-0
Container: 11 litre smart pots
Medium: Tiered soil - bottom half Biobizz All mix, top half Biobizz Light Mix. Both tiers mixed with 25% perlite and 3% EWC.
Temperature: 24-26c
Humidity: 65%
Feeding: Watered about 250ml every 2 days for the last week with Biobizz Root Juice @ 2ml/L. Intend to give them some Bio Silicon next feed @ 0.5ml/L.

Symptoms:
- Dark green foliage
- Leaves curling downwards
- Leaf edges curling up / distorted
- Leaves feel dry
- Twisting new growth

I think it is Nitrogen toxicity from a combo of extra EWC and the tap root probably going straight down into the Allmix. I've heard a report that the Sour Crack can be sensitive to Nitrogen too. I feel the growth has been impressive for day 16 and they are still growing (currently onto 5th node), I just hate to think the plants are suffering and their roots may be damaged.

The only step I've taken so far is to dim the light by 25%. I figured less light and lower temperature would reduce transpiration rates and thus the plants' nutrient uptake. Does this sound sensible?

I really want to avoid flushing. Firstly, because I don't want to disturb their roots. Secondly, I know that when these pots are sodden, they can take well over a week to dry out and these plants haven't seen a dry spell yet. Would letting the pots dry out before next watering help to reduce nutrient uptake until roots are more established or will it just damage them further?

I basically just want to know what the best course of action would be at this stage.

Oh yeah and check out lil' [HASHTAG]#6[/HASHTAG] pre-flowering day 16 with a cocktail stick for size reference. She's the most compact plant I've grown and unfortunately the least happy of this run. She has very dark green foliage under natural light and some yellowing of lower leaves.

This is my first run using tiered soil like this - I'm not going to give up on it but it certainly needs tweaking for future grows. Any help and advice would be great, so thanks in advance!

Sloth

 

[AutoWonders]

Nitrogen is from the "yellow" family. Those plants are in good shape for the early going. Be sure not to over or under water.

 

[Waira]

-- need more info mate,... distance of lights to plants,... and no feeds at all yet, right?

Pending light distances, no need to dial them down, better that you go 20/4 on sched.,.... yeah, reducing T can reduce transpiration rates, but the RH% has to play along too (go up),... Check out the article in Reference section on VPD, vapor pressure deficit, if you're not hip to it! ...this is the critical link between transpiration rates, T and RH% and the things that affect them,...
If this is N tox' it's very mild; sharply hooked "claw" tips are more tell-tale than this bowing down, though that can happen too,... Any overwatering recently? That can bow leaves as well,....
New leaves can distort for a variety of reasons, but often flatten out as they mature and harden up.... this will balance out better shortly I think, and since you aren't in bloom, nothing to sweat there either. If you had a worse case, more definitive, and had used a synthetic fert', a flush may be called for but you don't fortunately! Keep the inoculants coming, add some carbo' sources, this will help take the N levels down some while they feast on it and multiply,.. all part of the natural cycling of uptake and release they do, organics especially.... Look into using a humic-fulvic as well, nothing but goods there (alos an article in reference on them, and chelation).....
...yellowing lowers, I'd have to see,... one reason why I have reservations about this being N-tox, no way you have yellowing lowers with this! Could be something else, likely minor P defc. starting, as that soil is anything but complete for nutritional profile,... A little dash of mild bloom nutes (low N just to be safe) might help,... always remember, when you reduce a feed for one particular nute source, you're also shorting on all the rest,... It's good to have back-up supplements around when there's some custom tinkering to do! A micronutrient supplement, like Earth Juice Microblast is very handy stuff, it will cover all the bases outside of NPK....
Lastly, a soil pH probe is critical IMO, otherwise you are flying blind,.. organic or not, in-pot pH can drift out of range, you just don't pH adjust organic nutes is all.... the Accurate 8 is a good inexpensive unit, I love mine! Saves so many pain-in-the-ass fixing's down the road,... Forget run-off, it's a lousy measure of true in-pot pH for several reasons, it's only good for crude testing in a true pinch,.... otherwise, there's the more $$ electrode bulb type like Blue Labs (basically a modified pH meter, usually for liquids only), and all the care and products that entails!

 

[Sloth]

Thank you for your replies and Waira (don't know how to tag, i trust you'll be notified?) thank you for such a detailed response. I think the plants may have been slightly overwatered. The leaves picked up after letting the pots dry out a bit (particularly the dwarf with yellowing lowers). The dry period was also coupled with lower light level and lower temperature, which may haves helped. I have looked into VPD and have been trying to keep the tent within the optimal range.

The Sour Cracks are definitely showing signs of N toxicity though - dark green, dry leaves with sharp downwards claw on new leaf tips. No burnt tips to speak of, but there are somelight tips on new growth. The roots are coming out of the bottom of the smart pot though, which is nice to see.

The light is now 26" from canopy and on full power. One of the HLG reps recommended gradually lowering to 20" by the end of veg so I intend to let them grow into that range.

I'm planning to hold off on the nutrients until the leaves begin to lighten (there should be enough in the All Mix for a few weeks?). I'm glad you mention having supplemental feeds on hand, I was thinking of getting some pk booster to replace my bloom feed incase they are still showing N Toxicity after their stretch but I'm hoping they are happier by then. The microblast isn't available in my country but I'm sure I can find an alternative so thanks for the suggestion.

I fed yesterday 250ml each with 0.5ml/L bio silica, 2ml/L root juice and intend to alternate between that and molasses with the root juice instead. I don't want to add any calmag yet because it contains nitrogen. I have some organic magnesium - would you recommend using this at a particular time in the life cycle?

I don't water to runoff as I find it takes way too long for the pots to dry so I am just watering lightly every couple of days making sure the pots don't get too heavy or too light. I have used a soil ph meter but it's cheap and crap so I have just trusted the soil to buffer and only ph the bio silica feed down to 7.

Unfortunately, the runt hermied so I had to chop it. The middle plant looks like it might be developing pollen sacks too. It's funny, I initially wanted this to be a sea of green but only 8 out of 10 seeds germinated (hence 3 Bears og in the corner). From there 1 of the seedlings never grew it's true leaves, 1 has hermied and it's looks like another one might be too! At this rate there will just be a puddle of green by the end haha .

I've attached a close up photo - can you confirm if the plant is a hermie at this stage? The runt was my first ever hermie and had clear pollen sacks. This is not so obvious.

Really appreciate your detailed feedback and suggestions - I've only done a few runs so I'm still learning a lot and enjoying the process.

 

[Waira]

:smoking: ...slip the "@" directly in front of their name; if it's spot on, this little suggestion box with other similarly spelled names will pop up, and you just hit the right one, don't have to fill out the whole name...
--- VPD is a nice guideline, but in practical life, there's plenty of grey area,....
--- SC are sucking up the N in there like mad, hence the mild tox' and roots at the bottom already! Not much to do man, flushing will screw things up more than help, IMO,.... A little something that has no N in it can help, PK booster plus kelp extract, or other secondary/micronute source,....
-- HLG!! Fab' lights mate, I'm jeallie-
---

I fed yesterday 250ml each with 0.5ml/L bio silica, 2ml/L root juice and intend to alternate between that and molasses with the root juice instead. I don't want to add any calmag yet because it contains nitrogen. I have some organic magnesium - would you recommend using this at a particular time in the life cycle?

Si is excellent, Root Juice likely has humic-fulvic in it, also super good,... If the Ca-Mg is only 1-0-0, a little won't hurt,... may not need it yet though, if your tap water has significant hardness (mineral CaCO3 content),... a dash of the Mg supp' would be fine, covers a nute base there...

--- understood on the run-off,.. I'm guilty of that myself, even outside, but I need to do it more to flush the excess stuff out some,... indoors, I know you're hampered by slow dry-outs,... you can use a trick to speed drying : place a couple paper towles under the pot base, then on top of a small stack of news paper,.. wicking action will pull the extra water out much faster, if and when needed,....
... pH lower, the Si is pretty alkaline,... soil likes it around 6.5-6.3

-- be back later, gotta talk about that germ rate and hermies,....

 

[Sloth]

Thanks a lot for all that info - I'll definitely be using the newspaper trick to wick some moisture from the pots! I've been cutting a few leaves off hear and there as excess moisture has been accumulating where the big leaf fingers overlap. I'm just about to feed them some root juice and molasses - I hope they like it! I never had problems germinating in the past putting the seed straight into soil but last grow a Walter White never showed up. After that, I decided this grow to use the paper towel method in order to ensure that all the seeds germinated before planting. The plan, as mentioned, was a sea of green...

The plants just had their first dark period, which was 4 hours long. Afterwards, I notice this on one of the plants. Iron deficiency maybe? I've been hoping they would start to lighten up a bit but this is a bit extreme for my liking.

The pots still feel like they have some weight to them, despite the sides feeling dry/compact. This is when I normally water. I think I will start watering 500ml (up from 250ml) and wait 3-4 days between waterings to soak more of the medium. I'm sure there are parts of the soil mix which haven't seen moisture since the start of the grow.

 

[Sloth]

I've also just realised after watering 4 of the plants that my Root Juice smells like cat piss even though it's been open less than 6 months. I've watered the remaining 2 without it to see if they do better.

 

[Waira]

it's gone rancid!
.... OK that's classic Fe defc. there, you're right, way too light to be the normal paleness new growth can have,... So, either this is a simple lack-of, or maybe more likely your soil pH is too high; check the chart... it sounds like you may have had some dry-outs that were too much? This can make the soil oddly stubborn to rehydrate, and end up with dry patches in the pot,... a thorough watering with a wetting agent (Coco-Wet is great) will help penetration and more even wetting,... might be good to do this anyway, since we need to find out what the in-pot ph is,... run-off is not accurate at all, but in a pinch it'll have to do; use RO/Di/very low ppm water, (forget taking pH going in here), and water enough to get about 20% (of pot volume) run-off, collect the last bits for pH testing, after the really conc. stuff has past through some.... if it's way off, we'll know at least if it's needing correcting... if it's more or less OK, particularly on the acidic side, then we can safel conclude this is a lack-of defc. not a pH lock-out....

 

[Sloth]

The problem seems to have resolved overnight after watering with Molasses.

I did think it was odd how the plant was fine before lights off, then after 4 hours of darkness the lightness suddenly appeared.

With that crisis averted, unfortunately there is another issue - I was correct in thinking the middle plant was a hermie.

This is the only developed sack I could find. Can I just take them off as they develop? It would be a shame to ditch this plant as it is growing well despite the n toxicity.

 

[Waira]

...sometimes,.... well molasses does have a significant amount of Fe in it!.... K, Mg, Ca too..... uptake and transport are pretty fast in plants this size...

Ooo, I dunno about that mate, that's a full on male flower, far worse that a 'nanner.... Miss one open flower and it can knock up and ruin your whole crop, then you have clean -out protocol to do on the entire tent. Pollen and linger like any other dust.... your call!