SOIL Bottom leaves turning yellow

[kidane]

Hi everyone,

I started growing a few month ago and I've been reading this forum a lot. It helped me so much getting started, so thanks for sharing your knowledge!

I'm growing OG Kush for the 2nd time, and the first round went OK with decent harvest but they had the same problem of yellow leaves and lighter green between the veins quite soon after switching to 12/12.
I started from clones, they were good to put in soil after a week, then I let them grow for 2 weeks before switching to bloom 9 days ago. The bottom leaves started looking like on the pictures after 5 days.

I didn't give any nutrients during the 2 weeks of grow and started giving half of the manufacturer's recommended amount just after switching the cycle.
I inspected the leaves with a 60x microscope and didn't see any pests or eggs.

The guy at the growshop where i get my supplies told me to give them more nutrients after seeing the same pictures.

I've been told it might be Potassium, but also it might be magnesium .... Confused ...
Does anyone have a more precise diagnostic about what kind of nutrient deficiency is causing that problem, so i can really find out why it's happening again?


I'm also interested in any advice specific to OG Kush since I really enjoyed it and want to grow it again in the future.

Thanks

Space: L 35 x W 16 x H 43 inches (40*90*110 cm)
Light: 250 W CFL
Soil: Palgron Growmix
Organic Nutrients: Green Buzz Grow and Bloom
Water: Tap water
Extraction: 74 CFM (126 m³/h)

[OzzieWizard]

that looks to me like Magnesium shortage. Your plant will be scavenging Magnesium from the bottom leaves to keep the rest of the plant/s going. use CalMag. (OG Kush in a grow room? Crikey, my OG Kush grew 4 Meters high! you must have a big grow room ...) cheers !

[kidane]

I have a very small growroom actually and you're right they got me by surprise the first time.
That's why this time I didn't let them grow too long before switching, well i hope so ...
Thanks for the CalMag tip.

[OzzieWizard]

Mate ... I made a mistake! my giant Kush was OG Kush X San Bernadino Kush marketed as "Happy Valley". I grow Mango Haze mostly. big plants high yield high cbd. cheers!

[kidane]

Regarding the Magnesium deficiency, I double checked the pH and it was off, around 7.3 ...
Apparently the tap water where i leave as a pH between 7.4 and 8.
I hope increasing nutrients and correcting the pH will solve the problem

[Chefbjy]

With run off that high it will be harder for the plant to absorb magnesium. Lower the pH add calmag. And lower your pH when you water you should always pH your water you're giving your plants you're run off shouldn't change much but it's okay if it goes up out down a little 5.5-6.5 is ideal for plant growth.

[kidane]

Thanks guys, I got some pH down and will water today with good pH'd water.
How many days do you think it will take before I can tell if it's working?

Will the damaged leaves look healthy again? Should I remove them?

They're now 12 days into flowering and my plan was to free the bottom of the plants of new growth and stems before the stretch finishes.
Is it a good idea? Should I leave them alone until this magnesium problem is solved?

[D.A.A.S.69]

Morning Kidane, if they were mine, I'd wait a few days, before I did much training, or defoliating,

[kidane]

I've just watered them with water/nutrients mix at pH 6.2, and followed D.A.A.S.69 advice not to defoliate.
Unfortunately the run off was still quite high. Exactly 6.95 on my pH meter.
I imagine it needs a few watering to correct the soil's pH, or should i acidify the mix even more?
I had the feeling it was already a lot of pH down to get there... didn't want to over do it.

[Chefbjy]

I'd try to water with a 5.5 to get it down. At 7 the plant will have a tough time absorbing the mag. Once you fix your pH keep an eye on other leaves. The yellow ones won't turn green again but if more are yellowing then you haven't fixed it. Hope it goes well.

[kidane]

Alright Chefbjy i will add more pH down at the next watering...
Since i have to wait a few days for that, I will try in the meanwhile to spray them with an epsom salt solution so it doesn't worsen to much.
Someone suggested a 1/4 teaspoon epsom salt per liter of water, sprayed just before light goes on.
It seems harmless enough, right?

[Chefbjy]

I don't know about that. If it contains sodium no. Salts will make it harder to absorb the mag. I've never heard of that. But you can always look it up and look for another alternative that helps the plant absorb mag. Calcium is the only thing I know of that will help the plant absorb more mag. You may want to see what you can do to increase that if you keep seeing yellowing. Sometimes in flower it's natural to see the bottom turn yellow so I read somewhere here on gwe.

[kidane]

Hi Chefbjy, this is my second grow with the same strain, and the problem occured during the first grow. I didn't really try to fight it because I also thought it was normal in flowering but it spread badly. The harvest was decent for a first time but i'm sure it crippled them.

[kidane]

Mornin'!

Reporting back. As you can see on the picture, they're looking healthier than a few days ago.
I'm not noticing any aggravation, the yellowing is not spreading, the affected leaves got a bit worse though, but they are not many.
Even is the pH was not exactly ideal, i think it helped a lot already combined to higher amout of nutrients.

I don't know about that. If it contains sodium no. Salts will make it harder to absorb the mag

It's Magnesium sulfate MgSO4. But i'm no chemist so i don't really now if there is sodium...
After reading some Grow Diaries online, i found out that it's commonly used as foliar feeding.

This paragraph from wikipedia describes it.

In agriculture, magnesium sulfate is used to increase magnesium or sulfur content in soil. It is most commonly applied to potted plants, or to magnesium-hungry crops, such as potatoes, roses, tomatoes, lemon trees, carrots, and peppers. The advantage of magnesium sulfate over other magnesium soil amendments (such as dolomitic lime) is its high solubility, which also allows the option of foliar feeding. Solutions of magnesium sulfate are also nearly neutral, compared with alkaline salts of magnesium as found in limestone; therefore, the use of magnesium sulfate as a magnesium source for soil does not significantly change the soil pH.

I sprayed the 2 most affected ones with the Epsom salt solution. I'm curious to see if that helps until i get the pH right, will keep doing it for few days and report back.

[kidane]

Mornin'!

It's been 10 days and and they look healthy now. New growths are deep green and no yellowing in sight.
After 3 pH'd watering, the run off settled around 6.6 and i can see a huge improvement.

Regarding the Magnesium Sulfate solution as foliar feeding, I can't say for sure that it helped in any way but it didn't seem to have negative effects.

Thanks to you guys and your advice !!!
A huge hug to everyone!

[kidane]

When I posted 3 days ago about the general improvement, i hadn't noticed something new was happening at the top of the plants.
Top fan leaves started showing a lighter green spreading from the tip but it didn't look like a problem to my unexperienced eyes.
Today it's getting worse. I've been reading and looking but can't figure out what it is...

Appart from that, bud sites have developped significantly during the past week and growth has slowed down a bit.
It's the 19 th flowering day. So maybe it's normal at this stage and i'm just over worrying?

I watered them earlier on, pH in around 5.8, pH out between 6.5 and 6.8 for most of them, but 2 of them around 7.2 including the one that didn't really recover from the magnesium deficiency.
I'm following the nutrient manufacturer's recommendation.

The first picture was 3 days ago, the second one today.

What do you think?

[D.A.A.S.69]

Morning kidane, you sure need to get the run-off in the ones that aren't doing great to between 6.0-7.0. Then they can uptake your nutrients an start growing good again, they ought to be really growing good at that age.

[kidane]

Hi DAAS, sorry i realise now that my post wasn't clear, except one plant with the weird pH jump, mag deficiency seems to be gone now unless this new problem has something to do withit. The new problem affects all plants not only the ones with bad run off ... do you think it's also pH related?
3 days ago, all plants had a better run off around 6.6 even the ones mesured at 7.2 today ... can't really figure out what made pH jumps like that.

[GreenhouseEffect]

Hi kidane,
Have you ruled out light burn yet? The yellowing leaves at the top of the plant, with the veins staying green, kinda looks like that could be the problem.
Just burned the s*** out of my poor plants a couple weeks ago, so first thing that comes to my mind.

[kidane]

Hi, Is it possible with CFL's?

[kidane]

By the way if you're interested i opened another thread which is kind of episode 2 ...

https://forum.growweedeasy.com/forum/growing-community/get-help-for-marijuana-plant-problems/173494-ph-madness-can-t-get-it-down