Nute burn, underwatering stress or something else?

[jchesh]

Hi, I have a single plant setup in a kind of screenless SCROG / LST as pictured. It's a Sensi 'Mexican Sativa'. It was under 4 x 2 ft (96W) fluoros for veg and the first two weeks of flowering, and is now under a 150W HPS, and is six weeks into flowering.

It's in a 22 L fabric pot with Biobizz light mix. I fed 2 mL/L fish mix and 2 mL/L Alg a mic from about a month into veg, and then the same but with 2 mL/L bloom (so all Biobizz nutes too) when I switched to the HPS.

At the moment temps are 17°C min, 27°C max, read on the tent floor.

I'm now getting yellowing, necrosis, and curled crispy leaf tips, worse on lower leaves but affecting all levels as pictured.

I'm ashamed to say I did under-water it a bit, allowing it to fully wilt a couple of times a few weeks ago, my only excuse being that I have a busy life!

Does this look like nutrient burn, or a deficiency, or something else? Whilst the occasions of underwatering weren't ideal I didn't think that could cause symptoms like this, especially several weeks layer, and they seem to be getting worse... Any help would be greatly appreciated.

 

[Phytoplankton]

Kinda looks like a cal-mag or possibly a Potassium deficiency to me. Here's a chart that may help, there are others out on the web:

 

[jchesh]

Thank you, that's a really nice chart. Not sure if this helps narrow it down but I should add that a lot of the leaves, even the ones not showing yellow or brown areas, are curling up and going crispy at the ends (the last half or third of the central leaflet).

 

[Phytoplankton]

If they are canoeing, that's too much light (I really didn't see that in the pictures). Burnt leaf tips can be too much fertilizer or too much water, but the blotchyness on the leaves make me think deficiency (or perhaps lockout?) I am not familiar with biobizz growing media, is that like coco or like soil? Most of my growing is done in soil, so I rarely have deficiencies, unless I get a salt build up (lockout), then I superflush and restart nutes. I have found that in soil I like to get about 25% or more runoff, helps keep the salts from building up.

 

[FelipeBlu]

Alg·A·Mic is a revitalising product that contains a low level of NPK (Nitrogen, Phosphorus and Potassium) – making it impossible to overdose.

The Bloom has a NPK of 2-7-4 (not enough N and K and too much P).

All I am seeing are deficiencies of mobile nutrients - particularly N, K, and Mg - as the starving plant strips them out of the older leaves to fuel upper growth.

 

[jchesh]

Thanks guys.

If they are canoeing, that's too much light (I really didn't see that in the pictures). Burnt leaf tips can be too much fertilizer or too much water, but the blotchyness on the leaves make me think deficiency (or perhaps lockout?) I am not familiar with biobizz growing media, is that like coco or like soil? Most of my growing is done in soil, so I rarely have deficiencies, unless I get a salt build up (lockout), then I superflush and restart nutes. I have found that in soil I like to get about 25% or more runoff, helps keep the salts from building up.

They're not canoeing (if by that you means the sides of the leaflets curling up), just the ends (last third or so) are drying/crisping and curling upwards from the ends. Only on the larger leaves though.
Biobizz Light Mix is an organic soil with a lower level of nutrients than their All Mix. They even say 'When using Light·Mix you can apply larger nutrient doses to any kind of plant, including heavy feeders, without the risk of overloading the soil and causing a nutrient burn – indicated by yellowing and crunchy, burnt tips on the leaves.'

However I suspect nevertheless that I'm experiencing nutrient lock-out caused by watering with the above amounts of Fish Mix and Bloom straight after accidentally letting the plant wilt heavily, twice. Does this sound possible?

I've flushed with plain water now and removed the more damaged leaves. It is forming buds pretty nicely so I'm not hugely concerned, but at the same time it clearly doesn't look happy and while this is only my fifth ever grow I've never seen symptoms like this before. That said, this is the first grow I've done with this particular soil (previously used Canna Bio Terra) so I wasn't sure what rate to be feeding at. I think next grow I'll take the approach of not adding any fertiliser at all (except perhaps the Alg a mic) until I see deficiencies.

 

[jchesh]

Well...someone's really not happy. Here are some pics of what she looks like today, three days after I flushed with plain water and removed the most damaged leaves. To me it looks like it's basically dying, with most of the leaves (mainly the upper ones) going completely crisp and curling up. I'm a bit flummoxed now, and am wondering if it's a fungal infection or something because I can't see how with soil and organic nutes I'd have quite such a serious nutrient problem as this would have to be to give these symptoms.

I'm even wondering if it could be light burn, as the symptoms have really only appeared since I switched from the 96W of fluoros to the 150W HPS. Yes it's only a 150W but that's a fair bit of light for a 2x2 ft space with a single plant, and I know this strain is a bit more sensitive than the Skunks I'm used to growing.

 

[FelipeBlu]

I don’t think it’s light burn. The topmost growth looks great - even the nice white stigmas.

Your plant is cannibalizing the lower leaves because it is starving.

 

[jchesh]

Thanks FelipeBlu. I wouldn't expect such a serious deficiency to arise with the levels I've been feeding at (and the soil, although the Light•mix rather than the All•mix, was fresh) so am wondering if the deficiency is caused by overfeeding and lock-out. I've been giving 2 mL/L of Fish•mix, Alg•a•mic and latterly Bloom with every single watering though I've since read that with hand-watered soil one should alternate with plain water, and also start low and only increase if the plant tells you to.

I'm struggling to know what to (a) do about this now that flowering is well underway and (b) what to learn from it to do differently next time.

 

[Gabby987]

Hi jchesh

I'm going to chime in on this because I was having a similar issue and it was spreading to all the plants. I tried everything and nothing worked.

I always Ph all my fluids, but what I neglected to do was to calibrate my ph pen.

Once I fixed that, the problem corrected itself withing a couple of weeks.

 

[Buds Buddy]

Well...someone's really not happy. Here are some pics of what she looks like today, three days after I flushed with plain water and removed the most damaged leaves. To me it looks like it's basically dying, with most of the leaves (mainly the upper ones) going completely crisp and curling up. I'm a bit flummoxed now, and am wondering if it's a fungal infection or something because I can't see how with soil and organic nutes I'd have quite such a serious nutrient problem as this would have to be to give these symptoms.

I'm even wondering if it could be light burn, as the symptoms have really only appeared since I switched from the 96W of fluoros to the 150W HPS. Yes it's only a 150W but that's a fair bit of light for a 2x2 ft space with a single plant, and I know this strain is a bit more sensitive than the Skunks I'm used to growing.

This last picture. Can you get a pic of the darker green leaves with the spots in the bottom right corner of the pic ?
Then we can see what it starts out like & maybe pinpoint the issue. I think your main issue is you need Cal Mag.
They also look a little on the light green side meaning hungry. Do you pH your nutes ? Do you feed to 20% run off ?
When you flushed.... How much water did you use to flush with ? If that's a 5 gal. pot.... it takes 15 gallons of water to flush it correctly & remove any salt build ups that could throw your pH out of whack.

 

[Buds Buddy]

Hi jchesh

I'm going to chime in on this because I was having a similar issue and it was spreading to all the plants. I tried everything and nothing worked.

I always Ph all my fluids, but what I neglected to do was to calibrate my ph pen.

Once I fixed that, the problem corrected itself withing a couple of weeks.

I think we are both thinking the same thing.

 

[jchesh]

This last picture. Can you get a pic of the darker green leaves with the spots in the bottom right corner of the pic ?
Then we can see what it starts out like & maybe pinpoint the issue. I think your main issue is you need Cal Mag.
They also look a little on the light green side meaning hungry. Do you pH your nutes ? Do you feed to 20% run off ?
When you flushed.... How much water did you use to flush with ? If that's a 5 gal. pot.... it takes 15 gallons of water to flush it correctly & remove any salt build ups that could throw your pH out of whack.

So here are two images of some of the lower, less damaged leaves. In fact the upper sun leaves are the worst affected, followed by these lower sun leaves, with the smaller bracts and new growth looking unaffected. I know what you mean about looking a bit pale green generally but I think this is just the effect of the HPS light on the photo (even though I adjusted the white balance) – in the flesh the healthy leaves are a nice dark green. Btw, there's no sign really of any purple stems.

I don't pH my nutes, having read that it isn't usually necessary in soil with organic nutes, but I'm wondering now if this is a myth... When I water I usually use about 4 L (pot is 22 L) and have had to water roughly every three or four days. I'm wondering if this is wrong and not enough each time...yet this approach has always served me fine with the various Skunk varieties I've had before, as have the nutrient quantities. However, as well as this being a different strain, it is also the first time I've used Biobizz's Light•mix, having used CANNA Bio Terra previously.

I haven't done a full flush yet, just given a bigger water (c. 6 L) with plain water.

 

[Buds Buddy]

That looks like a Mag. def. to me. Cal Mag should clear that up if your soil pH isn't off. You could also use Epsom Salt for your Mg.

 

[Buds Buddy]

To a certain extent you don't have to pH in soil. But if your Tap Water is over 8.0 pH I would. I wonder if there's enough buffers in the Bio-Biz to control pH.
Personally, I pH every time, no matter what. I know if something does go wrong it's not my nute pH going in so I can eliminate that from the equation. Pretty good chance if I'm using fresh soil.... it's not the soil pH. Pretty much has to be a nute or pest issue then. Just the way I do things to make things easier.

 

[jchesh]

The pH of my tap water is 7.9 according to my water company (I don't have a meter...yet). Seeing as flowering is quite advanced now and the buds are looking pretty alright (see below...apologies for the dark bars, they're aliasing between the light flicker and my camera) I think I'll just go on watering with plain water for this girl – I'm not fussed about huge yields anyway as it's only for myself.

I'm considering going down the super soil route for the next grow. I find adding nutrients a bore anyway and never really know how much to add as there seems to be such a range of advice online and from the nute manufacturers themselves. And I like the idea of a truly organic/natural approach anyway. Might even order some earthworms...

 

[jchesh]

That looks like a Mag. def. to me. Cal Mag should clear that up if your soil pH isn't off. You could also use Epsom Salt for your Mg.

While I bow to your superior knowledge, the only thing that makes me wonder about whether it is Mg deficiency is I'm not seeing yellowing between leaf veins anywhere whatsoever which I thought was the initial signature of a Mg shortage? There are some yellow spots which then turn dead/brown but none of the larger scale yellowing with green veins that I always see in pictures illustrating Mg deficiency. Also it seems to be worse with large leaves at the top of the plant vs lower ones whereas I understood Mg deficiency symptoms to start at the bottom and move upwards?

 

[Buds Buddy]

While I bow to your superior knowledge, the only thing that makes me wonder about whether it is Mg deficiency is I'm not seeing yellowing between leaf veins anywhere whatsoever which I thought was the initial signature of a Mg shortage? There are some yellow spots which then turn dead/brown but none of the larger scale yellowing with green veins that I always see in pictures illustrating Mg deficiency. Also it seems to be worse with large leaves at the top of the plant vs lower ones whereas I understood Mg deficiency symptoms to start at the bottom and move upwards?

If your pH is 7.9 that is most likely your whole problem. Certain things in the nutes only get absorbed by the plant if it's in the correct pH range. More or less a pH Lockout type of thing. Not sure if or how it will effect the weed. I guess we'll know once you harvest & let us know.

 

[jchesh]

Thanks Buds Buddy. 7.9 did seem high to me and I wonder why it is as our water is also described as 'moderately soft'...although I know that hardness and pH don't necessarily correlate.

Definitely going to buy a pH test kit or meter and already have some citric acid for home-brewing and will dial it in properly for future grows. I think I hadn't bothered to test because of all the spiel from BioBizz about their soils and nutes being able to buffer etc.

 

[Buds Buddy]

I don't know anything about organic. The whole thought of bugs & worms in my house turns me off. You should check out some of @Emilya journals. She does organic & has many, many years of expertise on the subject. I'm sure she could help you a lot in that area.