safe range of calmag

starting to cool down, first frost here over the weekend. i want to supplement with CalMag to avoid issues i had last winter

say you have a typical 'balanced' nute mix of say 50 ppm Mg and 100 ppm Ca. and say finished EC is around 1.8. most of Ca in that mix is from CaN and most of the Mg is from MgSO4

Starting from that... what is a good addition of calmag? +0.2EC? +0.4EC?

i know there are safe ranges for both Ca and Mg but the Mg in CalMag is Magnesium Nitrate. (the calcium in CalMag is from CaN like my existing source.), wondering if the speciation makes a difference in absorption and or safe limits

Want to be careful as obviously these two compete for uptake, i dont want to create more problems than im trying to prevent

CobKits said:

i want to supplement with CalMag to avoid issues i had last winter

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did you have ca and mg deficiencies at the same time? what nutes? are you in coco?

that's the only thing i don't like about cal/mg: you need to add the sum of both to usually only fix one deficiency.

rockwool and last year i was getting symptoms of both in an extended cool period

GH calimagic recommended dose should have plenty of ca 5% for you. from calcium carbonate. but only 1.5% mg from mag nitrate. maybe add 0.5g/gal of epsom to boost mg a bit and get the added benefit of the sulfur too.

CobKits said:

starting to cool down, first frost here over the weekend. i want to supplement with CalMag to avoid issues i had last winter

say you have a typical 'balanced' nute mix of say 50 ppm Mg and 100 ppm Ca. and say finished EC is around 1.8. most of Ca in that mix is from CaN and most of the Mg is from MgSO4

Starting from that... what is a good addition of calmag? +0.2EC? +0.4EC?

i know there are safe ranges for both Ca and Mg but the Mg in CalMag is Magnesium Nitrate. (the calcium in CalMag is from CaN like my existing source.), wondering if the speciation makes a difference in absorption and or safe limits

Want to be careful as obviously these two compete for uptake, i dont want to create more problems than im trying to prevent

Click to expand...

0.4EC out of 1.8.

I use coco.

I use RO water that has 18 ppm, and use Advanced nutrientes coco line, wich has plenty a of cal mag, but some times a raise the inicial ppm to 120 of just mag, and then use the base nutrients wich is sensi coco grow and bloom. I just use bloom botles for Veg and flower.

What are your ratios of macronutrients? It's hard to overdo Calcium - excess Phosphorous is more likely to lock Ca and Mg out. A higher pH (6 in hydro, 6.3-6.5 in coco) will help with Ca and Mg uptake. I run an N-P-K-Ca-Mg ratio of around 3-0.5-4-2-1 in coco in winter. A lot of people forget to add phosphoric acid to the equation when pHing their water. It can add 0.1-0.2 EC. I never use P supplements.

Hi! I often hear about calmag deficiency on US sites...almost never in EU! Isn't it because of the water? I guess it is too purified so there is not enough calcium and magnesium in it to feed plants...i guess we have enough of it in our water to avoid the issue!
Have a lifted one

littlejacob said:

Hi! I often hear about calmag deficiency on US sites...almost never in EU! Isn't it because of the water? I guess it is too purified so there is not enough calcium and magnesium in it to feed plants...i guess we have enough of it in our water to avoid the issue!
Have a lifted one

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That is well considered, never noticed that with almost five years of growing with LED, and I'm based in Europe too. Only thing I noticed with LED it's how leaves become yellow quickly when I start flushing.

Prawn Connery said:

What are your ratios of macronutrients? It's hard to overdo Calcium - excess Phosphorous is more likely to lock Ca and Mg out. A higher pH (6 in hydro, 6.3-6.5 in coco) will help with Ca and Mg uptake. I run an N-P-K-Ca-Mg ratio of around 3-0.5-4-2-1 in coco in winter. A lot of people forget to add phosphoric acid to the equation when pHing their water. It can add 0.1-0.2 EC. I never use P supplements.

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id have to look at the spreadsheet. its jacks 3-2-1, maybe 3-2-1.5

Why not just buy calcium nitrate and then you could decide to use Magnesium sulfate, magnesium nitrate or neither. I'm guessing you're in hydro. The reason they use magnesium nitrate is to not include sulfate and calcium ions concentrated in the same stock solution.

It's very hard to go wrong with a 50 pound bag of calcinit.

Also, if you really do have a calcium deficiency, it's unlikely you also need Mg, and vice versa.

Without knowing your formula, I'm going to guess that the extra nitrate will be a good thing. Keep in mind that it's ammonium sources of N that are typically associated with N burn (glossy clawed under leaves).

Also, if you need more Ca, it's very likely you also need more N. (for what should be obvious reasons. You can't get enough nitrates from KNO3 without extremely high levels of K)

churchhaze said:

Why not just buy calcium nitrate and then you could decide to use Magnesium sulfate, magnesium nitrate or neither. I'm guessing you're in hydro. The reason they use magnesium nitrate is to not include sulfate and calcium ions concentrated in the same stock solution.

It's very hard to go wrong with a 50 pound bag of calcinit.

Also, if you really do have a calcium deficiency, it's unlikely you also need Mg, and vice versa.

Without knowing your formula, I'm going to guess that the extra nitrate will be a good thing. Keep in mind that it's ammonium sources of N that are typically associated with N burn (glossy clawed under leaves).

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the 2 in jacks-3-2-1 is CaN
the 1 is mgSo4

CobKits said:

id have to look at the spreadsheet. its jacks 3-2-1, maybe 3-2-1.5

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youre one of the first that i've heard jacks had multiple deficiencies.

gh maxibloom and some fulvics/humics/kelp for the win!

littlejacob said:

Hi! I often hear about calmag deficiency on US sites...almost never in EU! Isn't it because of the water? I guess it is too purified so there is not enough calcium and magnesium in it to feed plants...i guess we have enough of it in our water to avoid the issue!
Have a lifted one

Click to expand...

Yeah, limestone based ground water sources contain a lot of calcium and usually sufficient magnesium. It's dam water that's the issue - especially when it rains. The problem I have in winter is that our water comes from two sources (ground and dam/rain) and this year there has been a lot of rain, which has diluted the amount of calcium in the water. Also, with the water being softer, my nutrient lowers the pH to around 6.3 without the addition of pH Down (phosphoric acid). This caught me out initially, as I got lazy and didn't check my pH and continued to add the same amount of pH down and ended up with around pH5, less calcium in the water, and calcium issues showed up straight away. A little bit of Cal-Mag and no pH Down cleared it up straight away.

CobKits said:

id have to look at the spreadsheet. its jacks 3-2-1, maybe 3-2-1.5

Click to expand...

OK, well if I'm reading correctly and your total N-P-K-Ca-Mg ratio is 3-2-1.5-2-1 then I'd suggest you already have sufficient Ca-Mg and look at other issues, such as pH, reservoir temperature and P additives (if you are using them). pH alone will help make Ca more available. What do you run your pH at? A lot of guys add a lot of phosphoric acid to rockwool grows, as it has a naturally high pH. Not only can excess P lock out Ca, so can setting pH too low. Calcium deficiency can be a classic sign of pH issues. You haven't said if you're using RO water or tap water and how hard it is if you are.

Prawn Connery said:

OK, well if I'm reading correctly and your total N-P-K-Ca-Mg ratio is 3-2-1.5-2-1

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thats not the case. ill dig up the actual nute ratios when im home, and post them

ph?

When I used to use calmag I would add at 1ml per litre which worked out as a 0.2ec bump. Now I use an extra 0.2g per litre of calcinit & an extra 0.1g per litre of Epsom salt to mimic calmag supplementation.

I’m in the UK though so I expect my water supply already has a chunk of calcium & mag in it.

i bump magnesium by 50ppm, also with epsom salts. its cheap and easy.

I'm well off the normal recommended calmag ratio as i think my mag is quite a lot higher than it "should" be, everything is pretty much always happy though.

@Greengenes707 touched on this on one of his vids.

edit - i use RO and megacrop. according to their table, once i add epsom salts im at about 75ppm magnesium and 70ppm cal