I think I have a magnesium deficiency

[bobj]

First time grower here, I tried doing my due diligence to locate the source of the issue myself instead of just asking others to do my work for me.

I got yellowing in between the veins of my plants, mostly on the lower leaves. GWE says this can be due to one of six different issues, magnesium deficiency seems the most likely culprit. Reasons are because I've got red stems in addition to the yellowing on my lower leaves (this could be due to genetics, as my plant does sprout purple leaves in flower). Plants are grown in 5 gallon grow bags of the PROMIX herb & vegetable mix, I used PROMIX's granular fertilizer (4tbsp of the 4 1/2 tbsp recommended dose) and I have watered the plants twice since transplanting on July 5 (using approximately a gallon of water until runoff). Lights WERE too close, I've moved them up a few inches, highest plant sits about 18" from the light. I have not added or done anything else to the plants. Anything else you need to know about products used or growing habits, please ask!

What do you folks think? Is this a magnesium deficiency? Or is it something else? If it is a magnesium deficiency, should I use dolomite lime or epsom salts to correct the issue?

 

[HappyHazmat88]

Wutz up bobj howz the day goin for ya...and welcome to the forum ..I missed your introduction lol.

So reading through the ingredients listed for that medium it's looking to be more of a coco style grow medium where you have to feed daily and water daily(photos show cracked top medium--needs water)... And that would say your plant is hungry.

If ok I'm gonna call on someone familiar with this.... @Bill284 can you give insight please

 

[bobj]

Wutz up bobj howz the day goin for ya...and welcome to the forum ..I missed your introduction lol.

So reading through the ingredients listed for that medium it's looking to be more of a coco style grow medium where you have to feed daily and water daily(photos show cracked top medium--needs water)... And that would say your plant is hungry.

If ok I'm gonna call on someone familiar with this.... @Bill284 can you give insight please

Hi, it goes! I never wrote an intro..

So which of N, P, or K would you opine that it's lacking in? I have a soil test kit that I can test to see definitively. However, I do not think that is what is plaguing my plants, as the fertilizer claims to not need replenishing for 6 weeks. I fertilized and watered on July 11th, I shouldn't need to re amend my soil for at least another few weeks. I'm VERY conscientious about what I add to my plants, I didn't water my plants for close to three weeks and they didn't show any signs of wilting. This soil medium I believe has a high clay content, it tends to hold onto water for a VERY long time. There are more pieces of wood/sticks than there is coco content.

 

[Phytoplankton]

Make it easy, buy some calmag, that way it will take care of both Ca and Mg. Dolomite lime is a good amendment for soil, but takes quite a while to break down and become available to the plants. Unless your nutes have calmag in them, that's most likely your issue.

 

[cbdhemp808]

Good day Bob! By the looks of your 2nd photo, your plant(s) are doing just fine. The new growth looks great. I wouldn't worry too much about the yellowing older leaves... just pluck off any dead or dying leaves. But I also agree with what the others have said about your nutrients.

 

[bobj]

Good day Bob! By the looks of your 2nd photo, your plant(s) are doing just fine. The new growth looks great. I wouldn't worry too much about the yellowing older leaves... just pluck off any dead or dying leaves. But I also agree with what the others have said about your nutrients.

You think the plants are hungry? I can test the nitrogen content tomorrow, I need to go get some distilled water first. This might be heat stress from both the warm spell we just went through in addition to how low my light was.

The soil meter says the alkalinity is high. I can check the pH of the soil tomorrow as well. I want to wait and see what happens for a couple of days before I add anything to my soil. I'm thinking the best thing I might add to my soil might be epsom salts.. I have a fairly large bag from the dollar store that I paid a buck for. Are all epsom salts the same?

 

[cbdhemp808]

You think the plants are hungry? I can test the nitrogen content tomorrow, I need to go get some distilled water first. This might be heat stress from both the warm spell we just went through in addition to how low my light was.

The soil meter says the alkalinity is high. I can check the pH of the soil tomorrow as well. I want to wait and see what happens for a couple of days before I add anything to my soil. I'm thinking the best thing I might add to my soil might be epsom salts.. I have a fairly large bag from the dollar store that I paid a buck for. Are all epsom salts the same?

The new growth is a more pale green, but new growth is often like that. Your older leaves are deep green... good.

I think you are probably OK with this soil mix plus the ferts you are adding. Just keep observing the plants, and water them on a wet/dry cycle. If the pots are draining well when watered, there shouldn't be any problem. I noticed one of your plants is off center in the pot... you may want to reposition that one.

I recommend against epsom salt... there are better sources of magnesium... see the soil link in my signature.

The problem with the PROMIX you are using is that they don't list an NPK and guaranteed analysis for the product... they only say Feeds 3 months. So, there's no way of knowing the mineral content (calcium, magnesium, etc.) I see that the PROMIX granular fertilizers do list an analysis, so it depends which one your are using.

happy growing!

 

[bobj]

The new growth is a more pale green, but new growth is often like that. Your older leaves are deep green... good.

I think you are probably OK with this soil mix plus the ferts you are adding. Just keep observing the plants, and water them on a wet/dry cycle. If the pots are draining well when watered, there shouldn't be any problem. I noticed one of your plants is off center in the pot... you may want to reposition that one.

I recommend against epsom salt... there are better sources of magnesium... see the soil link in my signature.

The problem with the PROMIX you are using is that they don't list an NPK and guaranteed analysis for the product... they only say Feeds 3 months. So, there's no way of knowing the mineral content (calcium, magnesium, etc.) I see that the PROMIX granular fertilizers do list an analysis, so it depends which one your are using.

happy growing!

I'm using the other fertilizer, the one that doesn't contain magnesium. I'm thinking maybe I shoould just go and get that dolomite lime.

 

[cbdhemp808]

I'm using the other fertilizer, the one that doesn't contain magnesium. I'm thinking maybe I shoould just go and get that dolomite lime.

Cal-Mag would be better for watering in, since it's a liquid. FoxFarm, Botanicare, etc.

 

[Bill284]

Wutz up bobj howz the day goin for ya...and welcome to the forum ..I missed your introduction lol.

So reading through the ingredients listed for that medium it's looking to be more of a coco style grow medium where you have to feed daily and water daily(photos show cracked top medium--needs water)... And that would say your plant is hungry.

If ok I'm gonna call on someone familiar with this.... @Bill284 can you give insight please

Hey Hap sorry I'm late I had some things to take of this afternoon.
I take it he is in promix.
Full strength Nutrients at 5.8 either every day or every other day with water in between.
But fed daily is generally how it's done.
What is the feed schedule your using?




Stay safe
Bill284

 

[cbdhemp808]

Here's how Bob is feeding...

Plants are grown in 5 gallon grow bags of the PROMIX herb & vegetable mix, I used PROMIX's granular fertilizer (4tbsp of the 4 1/2 tbsp recommended dose) ...

So which of N, P, or K would you opine that it's lacking in? ... However, I do not think that is what is plaguing my plants, as the fertilizer claims to not need replenishing for 6 weeks. I fertilized and watered on July 11th, I shouldn't need to re amend my soil for at least another few weeks.

 

[Regrowth]

Peat's water retention is greater than coco's is and there's added perlite too... IMO they're hungry but because you started in a 5 gallon container you probably can't feed them enough because you're stuck waiting for the soil to dry out. Just a guess though. If you're ever having to water every day with peat then your plant is rootbound and needs a transplant.

 

[cbdhemp808]

Peat's water retention is greater than coco's is and there's added perlite too... IMO they're hungry but because you started in a 5 gallon container you probably can't feed them enough because you're stuck waiting for the soil to dry out. Just a guess though.

Thanks for pointing that out... the mix is 60-75% peat!! @bobj, are the pots draining well?

 

[bobj]

Thanks for pointing that out... the mix is 60-75% peat!! @bobj, are the pots draining well?

Pots are draining as well as any could, I believe. I usually use about a gallon of water to get run off. Sometimes a little less.

This might sound weird, but I think my pH is off. I'm seriously beginning to believe this is due to a lockout. Either my mag/sulfur is getting locked out, which is then creating a lockout of nitrogen. My soil meter is showing high alkalinity right now (8), and from what I've gathered, soil needs to be between 7-8, not above, not below.. I'm thinking I might need to lower the alkalinity a bit.

 

[Phytoplankton]

Pots are draining as well as any could, I believe. I usually use about a gallon of water to get run off. Sometimes a little less.

This might sound weird, but I think my pH is off. I'm seriously beginning to believe this is due to a lockout. Either my mag/sulfur is getting locked out, which is then creating a lockout of nitrogen. My soil meter is showing high alkalinity right now (8), and from what I've gathered, soil needs to be between 7-8, not above, not below.. I'm thinking I might need to lower the alkalinity a bit.

Not sure where you read that the soil should have a PH of 7-8:

"Cannabis plants prefer a slightly acidic environment for its roots. Growers using soil as their medium should adjust their pH to a range of 6 to 6.8. For a soilless garden, pH should sit between 5.5 to 6.5."

What's the PH of the water you're using after you add nutes? Also, something is not right, unless they put a ton of lime/gypsum in that mix, there's no way it should have a PH of 8 with all that peat moss and peat humus in it, unless the water you're using is alkaline to the extreme. Test your water PH. I think you may be on the right track with a lockout, because at that PH, the plants can't absorb some of the nutes. I would consider a good flushing (3X the volume of the pot size) to reset the soil. but you need to know the PH of the water going in. If you just dump super alkaline water on the soil, it isn't going to help much. Until you know the PH of the water, you're shooting in the dark!

 

[bobj]

Not sure where you read that the soil should have a PH of 7-8:

"Cannabis plants prefer a slightly acidic environment for its roots. Growers using soil as their medium should adjust their pH to a range of 6 to 6.8. For a soilless garden, pH should sit between 5.5 to 6.5."

What's the PH of the water you're using after you add nutes? Also, something is not right, unless they put a ton of lime/gypsum in that mix, there's no way it should have a PH of 8 with all that peat moss and peat humus in it, unless the water you're using is alkaline to the extreme. Test your water PH. I think you may be on the right track with a lockout, because at that PH, the plants can't absorb some of the nutes. I would consider a good flushing (3X the volume of the pot size) to reset the soil. but you need to know the PH of the water going in. If you just dump super alkaline water on the soil, it isn't going to help much. Until you know the PH of the water, you're shooting in the dark!

Yeah see, my soil pH is WAY over the limit! I got the number wrong.

I'm just using regular tap water & I'm not testing for pH. Also, I'm not using cannabis nutrients, the kind you pour into your medium. I'm using granular fertilizer, natural, organic kind. It's literally just the NPK value on the bag mixed with organic matter.

How do I go about testing the water pH? I have a cheap soil testing kit from Walmart, it's nothing fancy or sophisticated.

Edit: here are photos from the results of the basic pH test I did, flash on and off.

I'm thinking the soil is at the least, neutral (7.0) to slightly alkaline (before 7.5)

How does this affect the absorption of nutrients? Need I look into lowering the pH? Or do you think it's okay?

 

[bobj]

Okay so I just did a nitrogen test, there is plenty of nitrogen in my soil medium @HappyHazmat88

I have noticed that on at least one of my plants, some of the yellowing is turning to pink, indicating a SULPHUR DEFICIENCY. Strangely, non of the other yellow leaves are exhibiting this strange colour hue (yet).

Any way for me to test for sulphur?

 

[cbdhemp808]

Pots are draining as well as any could, I believe. I usually use about a gallon of water to get run off. Sometimes a little less.

perfect.

This might sound weird, but I think my pH is off. I'm seriously beginning to believe this is due to a lockout. Either my mag/sulfur is getting locked out, which is then creating a lockout of nitrogen. My soil meter is showing high alkalinity right now (8), and from what I've gathered, soil needs to be between 7-8, not above, not below.. I'm thinking I might need to lower the alkalinity a bit.

So I understand your pH meter is showing 8, while your test kit is showing what looks to me like about 6.8, which should be just fine. I don't know, but I suspect your meter is off.

I think you are OK, brother... just get some Cal-Mag liquid and incorporate into your feeding routine.

 

[cbdhemp808]

I'm just using regular tap water & I'm not testing for pH.

I would not use municipal water supply, which contains chlorine and possibly other undesireables. Well water should be OK, if you've had it tested. Tap water that goes through filtration, such as R.O., or other filtration system which also removes chlorine, is good. Rainwater is usually good. Store-bought drinking water is good.

I only use rainwater on my plants. I'm off grid, and that's what we have for our water supply... rainwater catchment.

 

[bobj]

@Emilya would you be able to render an opinion, please?