Yellow leaves…..again. please help

[CARmick93]

White widow near the end of the second week of flower and a few of the bottom leaves are starting to turn yellow and dry up.

This seems to happen every time during flowering with a few of my plants and I’ve never gotten to the bottom of it. Can’t get my head around it. I have always thought it to be a calcium or magnesium deficiency but I always add cal mag to the nutrients but doesn’t seem to fix it. By the end most of the leaves are yellow and crispy would be good to just get to the root cause this time to stop it altogether.

Humidity and temps are good. Temps are about 23 degrees Celsius lights on and 18 at lights off humidity is 40-55%.

I am using biobizz nutes at about half strength, bloom, fish mix, top max, algamic and also cal mag. No signs of other deficiencies or toxicities. Nutrients are phd to 6.4-6.6. Medium is plant magic soil supreme.

lights are marshydro tsw 2000w at about 24” above plants at 75%. There is good air flow with a circulating fan and good extraction.

if any one has any ideas or could shed any light on what’s happening it would much appreciated. Thanks.

 

[myke]

You have more then one plant so start experimenting.First suggestion is use just the plain fertilizer no extras,if that doesn't work buy different fertilizer.Second ,feed one much higher.Third ,change pH go higher.

Change to salts and feed to runoff,use an inert medium like peat or coco. Good luck.

 

[NanoGadget]

normally when I hear leaves yellowing starting at the bottom I tend to think N deficiency. Looking at the pics though, that isn't what N def looks like in my experience. just to satisfy my curiosity though, what is your source of N in you current feed regimen?

 

[NanoGadget]

something I forgot to mention that may help you diagnose problems is knowing the difference between mobile and immobile nutrients. immobile nutrients, once in use by a plant, is fixed in place and cannot be relocated by the plant and therefore deficiencies will start at the top of the plant. Mobile nutrients can be freely moved by the plant to meet its needs. As an example, N is mobile, so if the plant is N deficient it will move N from lower fan leaves to feed the more important new growth at the top. Know which nutrients are mobile and immobile will narrow down what the issue is.

 

[Masterdank420]

Looks like potassium deficiency due to magnesium toxicity.potassium deficiency starts from the bottom and works its way to the upper leaves. Potassium competes with the uptake of magnesium and vice versa. This is a common mistake people make. You can correct the issue but cutting out the cal/mag.

 

[Hairybuds]

Yup I concur, it’s a lockout of K because of too much Mg. Burnt leaf edges and tips with yellowing and clawing is K deficiency. I had the exact same thing and cut out the Epsom salts and bumped up the K and it resolved itself

K deficiency symptoms:

 

[Nutty sKunK]

White widow near the end of the second week of flower and a few of the bottom leaves are starting to turn yellow and dry up.

This seems to happen every time during flowering with a few of my plants and I’ve never gotten to the bottom of it. Can’t get my head around it. I have always thought it to be a calcium or magnesium deficiency but I always add cal mag to the nutrients but doesn’t seem to fix it. By the end most of the leaves are yellow and crispy would be good to just get to the root cause this time to stop it altogether.

Humidity and temps are good. Temps are about 23 degrees Celsius lights on and 18 at lights off humidity is 40-55%.

I am using biobizz nutes at about half strength, bloom, fish mix, top max, algamic and also cal mag. No signs of other deficiencies or toxicities. Nutrients are phd to 6.4-6.6. Medium is plant magic soil supreme.

lights are marshydro tsw 2000w at about 24” above plants at 75%. There is good air flow with a circulating fan and good extraction.

if any one has any ideas or could shed any light on what’s happening it would much appreciated. Thanks.

I use plant magic soil supreme. It must be amended with Dol lime.

Out the bag it tests pH 5.0-5.3. All goes well until flower then The pH drops in the 4.x zone which equals trouble.

Is your water soft?

I use 1 heaped tablespoon of dolomite lime per 10L of soil. Keeps the pH from getting too low.

 

[CARmick93]

You have more then one plant so start experimenting.First suggestion is use just the plain fertilizer no extras,if that doesn't work buy different fertilizer.Second ,feed one much higher.Third ,change pH go higher.

Change to salts and feed to runoff,use an inert medium like peat or coco. Good luck.

Ok thanks I’ll give that a go, what salts? Epsom salts? And next grow I’m going to try in coco.

 

[CARmick93]

something I forgot to mention that may help you diagnose problems is knowing the difference between mobile and immobile nutrients. immobile nutrients, once in use by a plant, is fixed in place and cannot be relocated by the plant and therefore deficiencies will start at the top of the plant. Mobile nutrients can be freely moved by the plant to meet its needs. As an example, N is mobile, so if the plant is N deficient it will move N from lower fan leaves to feed the more important new growth at the top. Know which nutrients are mobile and immobile will narrow down what the issue is.

Thanks a lot for the reply, I will look into it, like you say I don’t think it’s N deficient I’ve had that before as well and looks different to this. The fish mix is the source of N in the nutrients I use.

 

[CARmick93]

Looks like potassium deficiency due to magnesium toxicity.potassium deficiency starts from the bottom and works its way to the upper leaves. Potassium competes with the uptake of magnesium and vice versa. This is a common mistake people make. You can correct the issue but cutting out the cal/mag.

Ok thanks, wish I’d seen this sooner as I have just gave them another water with cal mag last night, so miss the cal mag for a few waters and bump up the bloom a bit for K boost?

 

[CARmick93]

Yup I concur, it’s a lockout of K because of too much Mg. Burnt leaf edges and tips with yellowing and clawing is K deficiency. I had the exact same thing and cut out the Epsom salts and bumped up the K and it resolved itself

K deficiency symptoms:

Ok thanks so how do I reverse the the lockout? Just drop the cal mag and feed a bit more bloom?

 

[Nutty sKunK]

Ok thanks so how do I reverse the the lockout? Just drop the cal mag and feed a bit more bloom?

You’ll be chasing your tail because it’s pH related.

Lime the soil or move to coco next run

 

[speedwell68]

I used to use Bio Bizz and Plant Magic. In the second week of flower you shouldn't be giving it all of those flower nutes anyway. Stick with the veg nutes until the end of the second week.

You'd be better off using a base nutrient all the way through. I have been using a complete Tomato feed, NPK 6-3-8. By the end of the second week I cut the Tomato Feed in half and add PK 4-8. Weeks 5-6 I will add a TBSP per gallon of Epsom Salt every other feed. Then at week 8 I stop PK 4-8 and feed half strength Tomato feed.

Have a look at the list of ingredients of a Seaweed based Tomato feed. It'll have Fe,Cu,S,Mg and so on. A complete feed, no messing with many bottles that cost a fortune.

 

[CARmick93]

You’ll be chasing your tail because it’s pH related.

Lime the soil or move to coco next run

Ph is always within the correct range though? I’ve read that it’s not even that important in organic grows as the soil buffers the ph anyways? And yes going to give coco a go next time round looking forward to seeing the difference between the two mediums.

 

[Nutty sKunK]

Ph is always within the correct range though? I’ve read that it’s not even that important in organic grows as the soil buffers the ph anyways? And yes going to give coco a go next time round looking forward to seeing the difference between the two mediums.

The soil will buffer the input pH very quickly.

What is your water source, do you know the ppm?

That’s true to a certain extent. The problems you are experiencing I had but I fixed them with dolomite lime. Let me explain;

After time soft water will acidify the growing media. This is because there is no/little calcium/magnesium present. You might read a high pH but again there’s a difference between pH and alkalinity. Soft water has low alkalinity. Yea you can add some calmag but it’s often too late. You need to add a buffer to compensate. That’s why I suggested lime for the next run.

Could mix 1tbsp into a gallon of water and apply. That’ll help get you to the end without further issues.

 

[Horselover fat]

Is it possible that your soil gets too dry? The colour kind of looks dry to me, but it could just be the lighting playing tricks.

 

[Masterdank420]

Ok thanks so how do I reverse the the lockout? Just drop the cal mag and feed a bit more bloom?

Drop the cal/mag altogether. Most water has calcium and magnesium present in sufficient quantities. Don't add the extra K or you'll run into toxicity issues. Just feed like normal and water like normal excluding the cal/mag and your issues should clear up.

 

[Masterdank420]

Ph is always within the correct range though? I’ve read that it’s not even that important in organic grows as the soil buffers the ph anyways? And yes going to give coco a go next time round looking forward to seeing the difference between the two mediums.

Coco is highly sensitive to PH. Just a little warning lol. If you go organic in coco make sure to PH your water to 6.5. Thats why i stopped using coco actually. My water is 7.7ph out of the tap so using organic soils to buffer the ph is more cost effective and takes less work. Something to chew on before making a switch.

 

[Hairybuds]

Coco presents its own challenges, you need to rinse it of salts and buffer it with mg and ca if it hasn’t been done already.

 

[CARmick93]

Coco is highly sensitive to PH. Just a little warning lol. If you go organic in coco make sure to PH your water to 6.5. Thats why i stopped using coco actually. My water is 7.7ph out of the tap so using organic soils to buffer the ph is more cost effective and takes less work. Something to chew on before making a switch.

Yes I’ve been researching it quite a bit and seems you have to get ph and the ppm bang on or you run into trouble and it does seem more hard work and time consuming then soil grows but just fancy giving it a go, I thought you couldn’t go organic in coco?