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Coco Peat Coir and dolomite lime

Bluey

Bluey

Well-known member
Does anyone have intimate knowledge for using dolomite lime in coco as a cal/mag buffer/additive?

i have run into strife now with cal/mag deficiencies in coco. I can easily up the mag with epsom salts but it still leaves me short on cal.

I have zero EC water before nutes. I plan on using silica until about 4 weeks before harvest.

I want relative stable pH at the roots. My last cal/mag micro additive caused rising pH in my nute tank which likely translated to rising pH at the roots.

Any better solutions I can give a go for initial buffering and ongoing supplimenting?
 
I use calcium nitrate in coco. It's super soluble so don't try to amend the coco because it will dissolve in the first watering. Use it every watering. It's a great base nutrient for the first 100-300 ppm. The other nutrient I use it's called peters profesional the hight intensity discharge formula. It's the same as jack hydro in the USA. Many "complete" formulas come without calcium and nitrogen because they're meant to be used with calcium nitrate. Mix right before watering and keep in a tight seal container because it will draw water from the environment and become liquid
 
I use GH Calimagic- calmag supplement for coco. Dose at 10ml/gallon for the initial soaking of the coco, then 5ml/G for the first few weeks of feedings. The binding sites on the coco must be saturated, otherwise the coco will bind the Ca and Mg so it will not be available to the plant.
 
Yes very true. It's called washing the coco. Leave soaking in hard water for 24 to 48 hours then rinse. Not all brand need to be washed. Only the generic bricks or sacks. Those canna, fox farms and other big brands come washed and ready to use.

Coco not only sucks calcium in those binding sites. But also dumps potassium in a "trade" cation exchange. So if not washed and flushed the already potassium rich substrate can create potassium toxicity preventing any calcium to be absorbed by the plant. A common mistake when this happens it's trying to flush the medium making a bad situation worse. What's needed it's to increase the EC with mostly calcium to feed the plant thru osmosis
 
I'm familiar with the starting with the bricks thing. Gave that up after one year, my time is more valuable than that. I use Mother Earth coco/perlite 70/30. It is supposed to be washed and buffered, but i have found that it still needs to be saturated with calmag before using to avoid calcium issues in the plants.
 
Thanks very much for that input. Very valuable.

I'll run some testing on the stability of the pH with the nute solution mixed. I always drain to waste. I'll hit up calcium nitrate first with epsom salts, nutes and silica in a test solution and see what happens with the pH.

Quality of bud as measured by perceived effects is what I am chasing (another subject), but it is so subjective I find as there are way too many variables we cannot manage at all or even measure yet. I am trying to reduce the variables in the grow output by managing the grow better. Am I wasting my time chasing these outcomes indoors to achieve consistsnt perceived effects? I couldnt achieve this outdoors in 30 years.

I'm going to have to test the leachate (runoff) but previous testing of this did not produce accurate or repeatable results. I'm new to indoor grows so pH is an entirely different management requirement to my previous soil grows (almost zero issues), even using a syringe to suck up the first of the runoff. Basically this testing was not reflecting the pH at the roots as it was hugely variable and showing results at times that meant my plants should have been next to dead but they were healthy as. I suspect residual compounds were throwing this way out, perhaps not so much in the coco but on the surfaces of the pot/trays...just don't know.

First grow I was running off the nute mix to flush about 1/5 out the bottom each feed. Second grow I didn't bother with regular runoff each feed but only once or twice a week. Some weeks early in the grow, never. Both grows exhibited cal mag deficiency in 1 strain and I caused other problems across the whole grow trying to correct this with incompatible additives that caused fast rising pH in my nute tank on my second grow over a 3 week period in mid flower.

First grow I was running max EC around 1.4/1.5 and second grow around 1.6. I'll up my EC again across the whole timeline from mid veg to mid/late flower in this next grow but the leaf symptoms are clearly cal/mag related. Leaf burn was showing a bit last grow but not greatly or causing issues.

This grow I'm reducing the number of plants in the grow from 4 to 2 and will stick to one strain which should make management easier but I need to sort my cal/mag issues and be better prepared.

This issue is really the only problem I can see that is stressing my plants and reducing both quality and yield, probably not greatly as the last harvest is smoking great but I do know I can and have achieved better. I am aiming for quality. Yield is fine at about a pound a plant.
 
Good to know. I've never tried mother earth. I use 250 liters a week so I buy in bulk non branded coco with no perlite
 
pH is hard to manage thru runoff. Just like you said. Many things get dumped by the plant. I like to control the pH going in and that's it. If you water often enough with full nutrient formula at the right pH eventually the pH will stabilize across the medium and runoff.

One thing is not talked about in begginer forums like this one is that the medium EC (inside the pot) needs to be much higher than the feeding values. Usually around 3 to 4 EC. This happens because the salts accumulate and it's not a bad thing. Of you water to runoff every single time the plant will show deficiencies in flower. But also if the ratio is not the right one an accumulation of potassium can lock calcium out of the roots. On the other hand, the decomposition of the coco fiber produces potassium available to the plant. But after a few weeks it decreases. So you need to increase the potassium ratio after mid flower. I like to use mono potassium phosphate (mkp) because it also improves bulking and accelerates flowering. It's the main ingredient in flowering boost formulas but you can get it very cheap off brand.

I have a small growing business, around 200 plant per year harvesting 4 plants a week with a continuous 32 plants flowering (harvest 4 and put another 4 to flower every week. 8 weeks = 32 plants) so I have very little room to try new strains. I've gone thru 35 strains or so during the last few years. And the strongest (most potent high) strain I have found is called descojack from delicious seeds. It's a cross between jack herrer(super silver Haze) and a mystery kush. I don't know if it's the haze but it's just more potent than all the others. So if you are looking for potency start with the right strain. This strain it's a big stretcher (over 6 feet high outdoors) and yields very very well. Big round buds with a very earthy smell.

One last thing. I'm guessing you are using a pH electronic wand to measure pH. I don't like them. They're just too sensitive and need calibration all the time and get you worrying about 0.05 changes. My advice is get some pH paper strips made for chemical laboratory reactions. Just aim for a pH 6. Paper strips, I swear to God, cheap and effective. Doesn't matter if the pH is 6.2 or 5.8. Try to ain at 6 and you'll be fine
 
Growing sativas and a couple of hybrids. Not high in THC. This current jar has been one that slowly comes over you but it hangs around for some time. Body feeling is where it's at for me. This one's a 50/50 body mind...relaxing. Works spot on for chronic pain. I have a bad tooth and it works long term very well on the pain. I can sleep and function well.
Using an Apera PH60 and careful to vary the pH going in typically 6 to 6.25 in later flower, but I vary it every week. Can vary it more if needed but tend to mix a 5 to 7 days supply in the nute tank at a time. Temp of nute mix hangs around the 18 to 20⁰C mark. pH in the tank hardly moves, nutes are stable for that period unless my supplemental calmag is not compatible...argh, that was a fuck up.
I've just given the coco a good flush ready for its 3rd grow. Havent dosed it yet. Tossing up to give it a couple of full veg nute flushes or hot shots I think they call them and then just keep up a couple of teaspoons per gal of the epsom salts and I'll test some cal nitrate with that.
Climate is pretty well nailed re temps & humidity and operate on a pretty small air changeover in the room but its fine..strong breeze in the room, everything moving around nicely.
 
Instead of dolomite which is CaMg(CO3)2, eggshell which is CaCO3 94% can be used to buffer coco although both of them are alkaline and raise pH of the coco media. There is a layer of organic material attached to the sell; remove it if you can before it dyies out.. Each egg is about 6 grams shell. But no buffering or additives during grow is needed if coco has been washed the right way.

* Coco holds water and water holds nutrients.
** Coco has cation holding capacity but RO water can slowly take cations from coco.

Soak coco at room temperature or higher but less than 60 C in RO water for a day or two(**); the more the water, the faster it rinses. then squeeze it well, really well(*), and collect its water and measure Electrical Conductivity of that water. If it is higher than target value of 0.2 mS/cm repeat the process of that soaking and squeezing again. After you reach that target in more or less 3rep in a week or more, dry coco to reach 20% moisture content and soak coco in normal feeding solution for a day. The plan is to raise EC to 1mS/cm. You can use double or triple dose of normal feeding instead of drying coco and don't forget to apply micro nutrient either. After all said and done you can grow in this treated coco without additives or buffering requirement if K/Ca ratio in nutrient solution is 4/3 or less.

If you wash your untreated coco with this method and then buffer it using recommended 100 meq calcium per Kg dry coco you will see potassium deficiency during grow instead of calcium deficiency.

coco strongly resists pH change when it comes in contact with nutrient solution. Every time i decrease pH of my untreated coco it takes me 60-70 meq nitric acid per Kg of dry coco in order to reach 5.6 from 6.6. You know? 1 Kg dry coco is about 10 litter after hydration and 60 meq nitric acid in 10 liter of RO water drops pH to about 2.5 and this pH 2.5 water still can't decrease the pH of 10 liter coco by 1 point. Generally nutrient solution pH does not effect pH of the coco media as plant can do with NH4/NO3 ratio in nutrient solution.​

1 more thing. Sulphate toxicity is rare but too much sulphate decreases Ca and Mg uptake. I found that many growers apply too much sulphate. Depending on VPD 10-15 mg/L sulphur as sulphate is enough for optimal growth. More than that will accumulated in the media without absorption. Remember solid MgSO4 is anhydrous epsom which i hate :). Don't use this compound if you don't know what you're doing.

To find out how much potassium and sodium has been washed from coco, you must know almost all EC of the collected water comes from potassium chloride and sodium chlorine which have EC of about 0.15 mS/cm per mole per liter. 10 liter of collected water at EC of 1.5 mS/cm contains 100 meq of those. Untreated coco contains 300-400 meq K and 100-150 meq Na per Kg dry coco. Good to know that Na will be washed much faster than K as it is lighter than K.
 
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Last auto grow I used too much nitrate based calmag and ended up with N toxicity. I then went to a trace element formula on a couple of them and a bit of dolomite lime in the water. It didn't work for me but I can't say why because of the prior N issue.

This run I only have a problem with the cal on one of 3 plants and I'm dosing it with about half recommended calmag nitrate again and pH around 6.2 to 6.3. The cal deficiency came on very fast on the leaves of the highest and largest colas on the sativa hybrid. This is a common problem with these genetics.

Anyway I'm hoping I can run this sativa hybrid thing for another 5 weeks or there abouts without too many problems. The other two will not need that length if time as they are frosty and cloudy now at about 55 days from flip.
 
Having stable nutrient solutions in open system is almost impossible with inorganic compounds as CO2 and carbonate spicies with change hydroponic solutions pH over time. If you have pH calibrating solutions check thier longevity although they are much concentrated than nutrient solutions. On the other hand, having stable nutrient solutions doesn't mean pH of media will remain stable at all. Although we adjust pH of nutrient solutions but pH in root zone is not much depend on nutrient solution pH as cation/anion uptake rate by plant effect pH much stronger than inorganic pH buffering ability of a hydroponic solution can handle.

Let me report you a valuable proposition. Adjust ammonium:nitrate ratio to 1:6-7 and you are almost done as it adjust cation:anion uptake ratio. pH adjust is necessary only if you add alkaline or acid compound in the nutrient solutions.
 
But genetic dependency of Ca has never been reported. You are the 1st at reporting such thing :)
If you see Ca deficiency in only some plants then perhaps the other ones are hungry for Ca although they have not shown the deficiency yet maybe because of different micro climate they experience like water, wind, RH, light and temp.
 
All plants are in the same room, same environment same nutes same everything except this time they got slightly more far red and deep reds spectrum.
 
But the same room doesn't mean same environment. Indoors, no 2 plants experience the same environment even if they are the same room. Indoor grown plants definitely receive different DLI and air so they experience not the same environment. If you have a light meter or temp meter or RH meter, take some measurements in different part of your grow room to better understand what I'm tell you.
 
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