Powdered fine gypsum is $11/40 lbs at the nursery. $8/50 for the sandy stuff.
1 Like
I don’t care for that Slownickel much. He was very against micronized snake oils until he realized he had his own profitable cult following.
Life advice: Don’t trust people who openly talk shit about their future business model.
3 Likes
Calcium is easily overdone in Cannabis. If there is calcium in your soil, Cannabis will obtain it. Cannabis prefers to be grown over intact bones, not pulverized bones. What kind of society has a soil full of pulverized bones… Cannabis hyper accumulates metals like Ca, so alot of conventional fertilizer knowledge doesn’t apply to Cannabis. In fact many Cannabis specific products are nothing but calcium antagonizers. Name one crop that soaks up calcium so easily in bloom that you have to reel the quality back in with PK boosters, pot mag sulfate sugars etc at harvest: Cannabis. That’s why Cannabis nutes come in 16 different bottles. There’s always some bully element pushing the other nutes around and in Cannabis it’s calcium.
1 Like
I use Roots Organics Elemental.
DERIVED FROM
Calcitic Lime, Dolomitic Lime, Gypsum and Fish Protein Hydrolysate
1 Like
In principle, that’s the main reason why I don’t like calmag products. Cation balance is important, and adding calmag without consideration to K creates a game of whack a mole.
PK boosters are somewhat safe to use in late bloom because the calcium requirements are reduced. Too much monophosphate can actually bind calcium. When you see white precipitation in hydro and coco systems, it’s mainly calcium phosphate that precipitates where water evaporates out and causes high concentration in the presence of high amounts of calcium and monophosphates. Polyphosphate products like GrowClean in place of MKP help to prevent precipitates and facilitate calcium uptake.
I have soft water and find a ppm ratio of 1.65:1 K:Ca is good for coco in early flower. After stretch, the ratio can be adjusted to 2:1. Keep Ca:Mg around 2:1.
You can also raise EC to add tolerance to the formula. The main issue is that this eventually creates N toxicity in most formulas. Mainly cation uptake is the challenge with cannabis. Anion sufficiency of NO3 (nitrate), P2O5 (phosphate), SO4 (sulfate) are very easily met, but nitrate has by far the lowest level before toxicity occurs. NH4 (ammonium) is a small molecule cation, and uptake is roughly 3x faster than nitrate, which makes it even more problematic for nitrogen toxicity in cannabis. Sodium is another cation that the plant doesn’t need hardly at all. It can only serve to suppress uptake of the other cations.
All of this mostly applies to soluble calcium. Calcium sulfate and calcium phosphate (bones) and lime have limited solubility, and don’t dissociate quickly enough to have a significant impact. Fine powders (micronized) of gypsum or lime have larger surface areas compared to rock and granules, so their rates of dissolution will be higher and have faster availability. Consequently it will also have a greater impact on the nutrient solution.
3 Likes
i really like the sensi calmag xtra. it worked well.
been using the GH one and it’s ok i guess. i have some issues in flower that i used to not have, but in veg it’s pretty good. you can over do the N though pretty easy with gh nutes.
are people running calmag past week 3 of veg?
Have not done this but it wouldn’t surprise me at all. I never have calcium problems, just magnesium. I probably could get away with just Epsom salts just fine. Especially if you are using bone meal or something similar. I imagine the calcium content of the soil would be fine.
I wanted to share this product because it’s peaked my interest. Canadian company, I think. Available on amazon.ca, too.
I’d like bag to try out, maybe.
3 Likes
Just an update, this dutch science nutrients company has failed to reply to every type of message I’ve sent them. Doesn’t inspire confidence.
4 Likes
Their packaging and their name makes me a little wary. It’s doubtful that “Dutch Science” has much of a science research budget at all. Seems to me that they mostly focus on marketing…
“Product of Canada” Love it. 
4 Likes
Haha. Yea, I duno what to think about them.
Calcium carbonate, and magnesium chloride. So should I just get some of those? Haha.
I’m literally one res. away from being out of my leftover GH MAGiCAL (calmag). I have all the stuff needed for custom blended fertilizer mixes. But to finish this grow (not in flower yet) I just want to add something to the 5-12-26 to satisfy the coco coir, without adding nitrogen. So no extra Calcium Nitrate, no Magesium nitrate, etc.
What should I use/get, guys?
I have Magnesium Sulphate (epsom). And this “fancy” Calcium EDTA (see custom hydro nutrients website, or I linked it in an earlier post, I think).
Should I get Calcium Sulphate - I can’t afford to order “the best stuff”, the stuff that might be closest to water soluble, from the USA right now (I’m in canada).
Should I get Calcium Carbonate?
Calcium chloride?
I think the only of these forms that’s really close to fully water soluble is Calcium Chloride, right?
Thanks.
1 Like
Calcium chloride is good as a water soluble supplement for calcium. You can’t use it to satisfy the whole calcium budget, but calcium nitrate should be carrying most of that burden. It’s also very cheap. The only time I would say you really shouldn’t use it is if you are using pool shock for sterile reservoir, because that is already a chlorine based product.
I think people are a little to hesitant about using it, but it has been commonly used in agriculture for a long time and it’s primary usage has been to increase calcium without raising nitrogen. It works great in foliar applications, but if you’re like me you don’t do foliar anything after stretch. In the amounts you would use it to augment 5-12-26 formulas (probably ~0.25-0.5g/gal), it’s safe. Chloride even antagonizes nitrate, so that’s no even a bad thing.
7 Likes
A key consideration with calcium sulfate is also that its dissolution kinetics are slow. It takes a significant amount of time for a given amount of calcium sulfate to dissolve in water, even if the thermodynamics favor the dissolution of the salt at the temperature your water is at. For this reason it is very important to only use calcium sulfate sources that are extremely fine and are graded for irrigation. This is sometimes known as “solution grade” gypsum. I advice you get a small amount of the gypsum source you want to use and test how long it takes to dissolve 0.05g in one liter of water. This will give you an idea of how long you will need to wait to dissolve the calcium sulfate at the intended temperature. Constant agitation helps with this process.
I think this is a good article about solution grade calcium sulfate. It seems like it might take quite some time to dissolve, but is a great option for mixing into coco I think.
4 Likes
EDTA is horrible if you grow organically. It’s like pouring salt on your microlife. Sounds like you’ll be fine in coco with liquid nutes, ( unless organic) but I had edta kill my plants years ago, so I warn people at every opportunity now. Stressed my plants so badly from just one use, they got some sort of wilt and died in just a few days.
4 Likes
Why is that?
1 Like
To me, it’s an unnecessary risk for something I’ll be smoking. Praise the flying spaghetti monster and knock on wood, but I haven’t ever felt like I couldn’t fix a problem other ways once the buds start popping.
This is what I swear by. I buy a whole 2lb bag for a years worth. This is definitely in short supply, only 10 bags when it came back in stock recently.
2 Likes
I run all coco. Was using just GH CalMag the for the first year and recently started using half GH CalMag and then tossing in epsom and DTE Cal 96. Not sure I’m liking the outcome and might go back to just the GH CalMag. Does Cal have to be chelated for uptake into the plant? (I’m trying to sound like I sort of know what I’m talking about)
4 Likes
Yea. I don’t typically do foliars, except maybe wettable sulfur for ipm, early on though - in veg.
Any idea the elemental ppm of calcium that application rate would provide? I might want something I could also use after cutting jacks out completely, so I duno if Ca sulfate of Ca carbonate would be good/better for that. Maybe. I guess if I’m in coco coir, I don’t need to worry about the Ca carbonate or sulfate not being totally water soluble – except it might be an issue for pumps, or reservoir? I don’t wanna hand water.
Thanks.
I should have checked the very resource I suggested other check out, I guess. Haha, thank you.
I’m using ‘synthetic’, Jack’s at the moment. But thank you, I appreciate the heads up.
Thanks man. I will check it out.
Yea, I’ve pretty much only ever used GH CalMag, in the rare instances I used CalMag at all.
I’ll try and sort of know what I’m talking about too: Calcium is immobile, it relies heavily on transpiration (VPD, particularly RH). So that’s a big factor in uptake. But I’ve read that chelation is very important too. One ways are the EDTA (and similar) types, and also amino acids (humic and fulvic, both I think).
Anyone can correct me if I’m wrong.
Thanks again, guys.
4 Likes
Calcium chloride is fully soluble ~34% calcium. 0.5g/gal provides 43.5ppm of Ca and 78ppm Cl. But even half of that should be plenty.
If you use calcium sulfate (gypsum) or calcium carbonate (lime) you can pre-mix them with your medium. I’m considering trying a non-solution grade granular version of gypsum, because it’s very cheap and slow release. I can buy a 40lb bag at the hardware store for $15.
Last thing that usually doesn’t get discussed is that calcium deficiency can happen easily with inconsistent moisture levels. If your coco goes completely dry, I’ve noticed that I almost always get a deficiency afterwards. Stay on top of your watering, especially early flower when they start chugging a lot of water and it might solve a lot of problems.
That’s one reason why hempy buckets work well with coco. You have a little reservoir to help buffer your moisture.
6 Likes