15 plant coco grow, recurring Nutrient/Magnesium deficiency problem

Hi, I`ve had a thread in the infirmary section, but after a suggestion from another, perhaps this is a better place for me to find the answers to my problems.

I`ve been growing Cheese for 3 grows now, including this one and been having real issues with what I think is a magnesium deficiency problem. My 1st grow yielded around 4/5ths of what I`d expect from my set up (I`ve known the plants well through a couple of mates that were growing it), during this grow I did notice a fair amount of intervienal yellowing of many leaves, particularly older fan leaves, but did nothing to treat it, and cant remember too many details of when things started to show. The last grow was a disater and only yeilded 19 oz from an expected 60+. It was too late before I realised what was happening as I`d let myself get too distracted (lovely lady!) and sloppy with my aproach to my grow. It was too fucked by the time I realised what was going on to help them.

This grow I`m back on it and trying my hardest but I`m still having big problems with the magnesium deficiency.

Each plant is a clone from a friends grow who has no such issues, I think she grows ebb and flow using auto pots.

I take them from the plant and dip them in Clonex cloning gel then into jiffys pre treated with Rhizotonic. I usually get around 100% rooting and select the strongest ones. They always look to be struggling a bit and some interveinal lightening occurs. I foliar feed them to help with this and they usuall pick up. When rooted I put them into 4inch pots and introduce them to nutrients at a strength of around EC8 until they show a few roots through the bottom of the pots. I then pot them up in 7ltr pots for the rest of the grow.

Each pot has a 70/30 mix of coco/clay pebbles, with an additional 3 or 4 cm layer of clay pebbles at the bottom to assist drainage.

Nutrients were cana coco, but I`ve changed during this grow to Atami`s B`cuzz coco A+B along with there recomended additives B`cuzz booster and B`cuzz bloom stimulator. (The problem I`m having now has occured with both the Cana and the Atami nutes).

I have 5 plants in each of 3 60ltr hydro tray/res` in a room that measures 12 feet by10 feet (minus a chimney breast), 15 plants in all. I have a 600w sodium over each tank, total of 1800watts.

Each plant is fed with a dripper, the term being used loosely as I`ve removed the dripper nodes from the ends and have a free flowing trickle when the pumps are running for 4x 45minute on cycle during lights on.

The air is circulated around the room with 4 stategically placed desk fans, and two extractors with carbon filters one 4inch and a 5 inch. Intake is passive through a vented door.

I hope that covers the set up, any more info needed, please ask.

My problem is I think a magnesium deficiency, but I dont know what is causing it.

During the veg cycle they started to show very serious sugns of Mag def. I found that my ph pen was badly callibrated and instead of giving them nute with a ph of 5.2 to 5.4 it was really in the high 4`s. I corrected this and treated with epsom salts. After this they`d drink up nutes at EC15 with a stable ph. I let them recover well before switching to 12/12 lights and as a result they got quite big, but they carried on into flower really well and lots of branches and lots of developing bud sites. the leaves all looked a little light and limey but were growing well.

All was going well until around 10 to 14 days ago I noticed the interveinal yellowing creeping back in. 1st thing I did was check ph, double checking with liquid drop tests and measuring the ph and EC in the res and the run off from several pots, but all checked out ok. They also starded to stop drinking up so much nutrient and the res Ec always increased as they went down. Ph had remained stable except one res did an unusual drop to 5.3 (from 5.8) whereas the other 2 remained stable. ( could have been my error, but I`ve been so very careful I do doubt it).

I`ve been treating for around the last 7 days with Epsom salts at 1/2 teaspoon every 5 litres. Its hard to say whether I`m on top of the problem or not. There are a lot of leaves showing the yellowing but its hard to tell if there are more leaves turning that way or not, but its definitely not spreading as rapidly as a week ago, bud development seems to be going well still sa the colas begin to form and the buds start to join together, but I daren`t speak too soon, until I have this issue sorted. Of course the affected leaves wont get better but I hope as these die off there wont be others going the same way. One thing I noticed is that the large leaves nearer the lights (heat source are a little worse affected than the others, but only marginally)

Due to the res EC rising quite a lot as the res is used up I have refilled the res` with a fairly weak nute solution of EC12-13 and added Epsom salts 1/2 teaspoon per 5litres, which has raised the Ec to 15-16, I have the ph across all 3 res` between 5.5 and 5.7. I`d like to get em drinking a stronger nutrient strength without the Epsom salts as I`m sure they`ll be needing the food for bud production if they`re to do ok.

The picture link is a pic of my last pathetic crop near to harvest, it was horribly stunted.

Here are a couple of pics of the current grow when havin problems in the veg stage

pics day 9 of 63 plants recovered nicely

pics day 9 of 63 plants recovered nicely

Here are a couple of the current grow around day 9 out of 63 of 12/12, as you can see they`ve recovered well.

Pics Day 17, mag deficiency returns

Pics Day 17, mag deficiency returns

Doesn`t look bad on the overall pic but if you look carefully or at the next pic you`ll see its coming back with a vengeance.

Pics yesterday, day 26/63 of 12/12 mag deficiency

Pics yesterday, day 26/63 of 12/12 mag deficiency

I took these yesterday, the buds are continuing to develop and get resinous, but the stress they`re suffering sure cant be doing the final yield any good.

Has anyone got any ideas as to why I`m getting this problem recur?

I`d really appreciate any constructive feedback

this happens in hydro nft too , i just add magnesium every time i feed but this can imbalance the calcium and so on ,, its a mine field with deficiencies tokesome ..

Hi Tokesome,
Your last crop sure was a disaster...now I understand why you're so concerned. I don't know anything about the specific nutrients you're using, but since this problem was occurring with two different nutes...I think it's safe to assume it's something else. Your Bcuzz nutes have almost 1% mg so it's being locked out by something. Coco can be finicky. I don't recall what you're using for water. The problem is likely either water or coco related. Let me ponder and I'll get back to you.
ET

EvilTwin said:

Hi Tokesome,
Your last crop sure was a disaster...now I understand why you're so concerned. I don't know anything about the specific nutrients you're using, but since this problem was occurring with two different nutes...I think it's safe to assume it's something else. Your Bcuzz nutes have almost 1% mg so it's being locked out by something. Coco can be finicky. I don't recall what you're using for water. The problem is likely either water or coco related. Let me ponder and I'll get back to you.
ET

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I`m using tap water mate, it reads EC3, I`ve always used tap water for about 20yrs as too much hassle to get the amount of bottled water required to my grow. Yeah the last one was appalling mate and fair broke my heart! I`m sure the problem was exasperated by the extreme summer temps just when it counted, but I`ve grown through the summers for many years before with no such problems. I`ve had a few years experience with nft hydroponics but pythium came a knocking and have since been in coco with great success for many years. I`ve never had such problems. The only problem I`ve had with coco in the past has been with root rot due to having no clay pebbles in the medium to assist drainage combined with an infestation of gnats. The plants are looking better than the last grow but now the problem has re occured I`m obviously very worried. If this one goes pear shape its going to be a big disaster for me.

I think the Epsom salts may have arrested the problem or at least masked it a little as the yellowing doesn`t seem to be getting any worse. I cant see it being a strain issue as I know the same stock is doing well elsewhere. Sure wish I could get on top of this and get rid of the problem.

I`m a bit surprised nobody has chipped in from the number of people reading the thread, if anyone out there has an idea as to what is going wrong here please let me know. Obviously some sort of deficiency or lock out is going on, but I cant figure out why.

Thanks, Tokesome

Your pH, at 5.2-5.4, is WAY too low for coco. Try it between 5.9 and 6.1 and watch the improvement.

I`ve just been in the grow room and sadly the yellowing does seem to be getting worse, I dont know if its previously affected leaves getting worse or if its getting worse generally, I hope the former but suspect the latter.

After two 45min feeds one a couple of hours before lights out and one an hour or so after lights on the EC has risen by 2 in two tanks and by 1 in the other and Ph has risen from ph5.6 to 5.9.

It seems my girls are not wanting to take up the nutrients or I`m over feeding, its so frustrating to see this happening and not being able to do anything about it.

Wait...What? said:

Your pH, at 5.2-5.4, is WAY too low for coco. Try it between 5.9 and 6.1 and watch the improvement.

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This is the first time I`ve had my ph as low as 5.5 or 5.6 (not 5.2-5.4) in ages, just to see if this would make an improvement. For the past few weeks I`ve kept them between 5.8 and 6.2, and the problem has occured in those conditions. The ph has risen again as you`ll see in my post above. I`m sure this isn`t a ph issue, I`ve checked with the ph meter and liquid drip tests, and also checked my run offs.

What do you guys think to the idea of flushing with plain water?
I`m in 2 minds, on the one hand if I have a build up of something it may reduce it, then start with fresh nutes, on the other hand I dont wanna take food away from these plants if its going to starve them further.

It seems the more I learn the less I understand.

do a flush tokesome so you can clear the old nutes and salt build up make sure the water ph is about 6.0... then feed a bit lighter ................................

Tokesome said:

This is the first time I`ve had my ph as low as 5.5 or 5.6 (not 5.2-5.4) in ages, just to see if this would make an improvement. For the past few weeks I`ve kept them between 5.8 and 6.2, and the problem has occured in those conditions. The ph has risen again as you`ll see in my post above. I`m sure this isn`t a ph issue, I`ve checked with the ph meter and liquid drip tests, and also checked my run offs.

What do you guys think to the idea of flushing with plain water?
I`m in 2 minds, on the one hand if I have a build up of something it may reduce it, then start with fresh nutes, on the other hand I dont wanna take food away from these plants if its going to starve them further.

It seems the more I learn the less I understand.

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Can you Foliar feed with Cal/MAG and see if that helps, then you will know if it is you medium or something else. I have been having a similar problem and it seemed to help without creating toxic build up

indicapimp said:

Can you Foliar feed with Cal/MAG and see if that helps, then you will know if it is you medium or something else. I have been having a similar problem and it seemed to help without creating toxic build up

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I`m a bit worried about foliar feeding as they are 4 weeks into flower and dont want any residue on the bud, along with the threat of mould and burning the leaves. I have a few little ones going at the moment and I`m foliar feeding them. To be honest though. I`m thinking of a different strain for my next ones if I cant get to the bottom of this issue

I`m wondering, but probably nothing to do with this problem, but I don`t use air pumps to oxygenate my res. I used to in hydro and started to in coco, but my friends found they didn`t need them in coco so I haven`t bothered for the past few years. I could do without the additional wires and sockets in my already overcrowded room, but of course if needs must. I`d need to get air stones but I do still have the pumps so I may try running them to see if that will help. I gather though if the problem was lack of oxygen they`d most probably be showing different signs. Any thoughts on this guys??

Thanks, Tokesome

do you have an anti-syphon valve on your drip manifold? ie when you turn off the pump does all the water stop coming out of ALL the outlets? what are the temps in the room? what is the temp of the res? How big is your res? How often do you change it out? You might be watering too much with open lines for coco... can you take any of the plants out of the pots? if you can pick the worst one and check out the roots; or smell the pot; you can smell bacterial conditions if the roots are rotting. Check the roots and see if they are healthy or stressed. Drain all your tanks and fill with plain water; flush, flush, flush.

What is the quality of your tap water? PH? EC? etc.. do you let it off gas to get out chlorine? can you afford enough tap water to try an experiment on one tray? if it's the water the cost of a ro unit will pay for itself in extra yield once the problem is corrected.

maybe try a little plasma ultra filtrate aka urine ,, one cup per gallon.. looks like your low in nitrogen n maybe some mag, typical coco problems, buds are growing huge admist a huge deficency of some sort. if you uped the ph to around 6 and your not seeing improvements i guess its not mag related.

From:

Controlled Environment Agriculture Center
University of Arizona

The levels of pH and alkalinity (measured as carbonates and bicarbonates) of the raw water affects the absorption of certain nutrients by the roots. Water pH levels above the desirable range (5.0 to 7.0) may hinder absorption of some plant nutrients; pH levels below this range permit excessive absorption of some nutrients, which may lead to toxic levels of those elements.

Nutrition(11 September 2009)
==============

That said, they also recommend as folks do around here 5.5-6.0 for hydro. Coco is still a dense medium though, so I think the pH should range from 5.5 to 6.5.
What you water at and runoff are different than what's going on down inside the pot. You'd need to get a handful of medium from down deep in the pot to check pH. It is probably off.
Just my guess, but since your plants seem to have deficiencies and not toxicities, then I'd guess something's being locked out, and i'll go learn more and be back. That is assuming you are feeding enough.
edit:
incomplete info, check later post for more accurate info

opt1c said:

do you have an anti-syphon valve on your drip manifold? ie when you turn off the pump does all the water stop coming out of ALL the outlets? what are the temps in the room? what is the temp of the res? How big is your res? How often do you change it out? You might be watering too much with open lines for coco... can you take any of the plants out of the pots? if you can pick the worst one and check out the roots; or smell the pot; you can smell bacterial conditions if the roots are rotting. Check the roots and see if they are healthy or stressed. Drain all your tanks and fill with plain water; flush, flush, flush.

What is the quality of your tap water? PH? EC? etc.. do you let it off gas to get out chlorine? can you afford enough tap water to try an experiment on one tray? if it's the water the cost of a ro unit will pay for itself in extra yield once the problem is corrected.

Click to expand...

The drippers are fed by pumps, when its off there is no feed going to any pots, they run by gravity back to the tanks, when the pump comes on it takes a bit of bubbling and spitting from all the drippers before they flow.

I`ll get my thermometer back from my friend and check the room stats, but I`m pretty sure both the room temps and res temps are ok, especially this time of year in the in northern Europe, but I will check it out and report back.

Res` are 60ltr each (3 of them). I tend to change them out once a week, and top up half way through to adjust, of late, for the rising EC values.

You say that 4x 45 mins open drippers may be over feeding, what regime would you suggest, ie number of feeds and duration.

I cant take any of the plants out of the pots, they`re all inter twined and now some of the long side stems are being supported to wires above. One or two of the worst affected are the plants that also look the strongest. I have a feeling that they are suffering now as they are trying to use energy to put into bud production. I`ll get down at the pot level and see if I can notice or smell anything out of the ordinary.

My tap water is EC3 and ph7. I tend to change the res after their last feed so the mixed solution rests fo 12 to 14 hours before going to the plants.

I haven`t changed my methods in some time and haven`t had issues like this before, but there is something a miss here for sure.

Yeah I think I`ll flush for a day and then reset with fresh nutes. Given that there is a 1% Mg content in my nutes, do you think I should also carry on with a maintenance dose of Epsom Salts.

I`m very skint at the moment so dont wanna spend on unnecessary stuff, but I`m thinking about getting airstones and airlines for my airpumps tmro, can someone tell me if its a necessity for coco growing fed from a res?

All the leaves directly around the buds look a healthy green, but its not only the big leaves that are showing these signs, My main concern is stunting of bud production as its quite a critical time for them 4 weeks into 9 weeks flowering.

Thanks, Tokesome

hazy said:

What you water at and runoff are different than what's going on down inside the pot. You'd need to get a handful of medium from down deep in the pot to check pH. It is probably off.

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Yeah I understand the very basics of how ph affects the uptake of nutrients mate, but my ph has been kept in range overall. How do I test the actual medium, assuming I can get some from deep down in the pot? Tokesome

Leviathan said:

maybe try a little plasma ultra filtrate aka urine ,, one cup per gallon.. looks like your low in nitrogen n maybe some mag, typical coco problems, buds are growing huge admist a huge deficency of some sort. if you uped the ph to around 6 and your not seeing improvements i guess its not mag related.

Click to expand...

Heh heh, you suggesting I piss in the res. It could be quite toxic at times