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What's a good ratio of Ca/Mg?

U

UnKnown

New member
Hello folks,

On reading my water report a couple things stuck out -

Calcium - 103 mg/l
Magnesium - 8.57 mg/l

That's a ratio of 12:1, which seems well out of tune with the requirement of growing our favourite plant. It would also explain the severe Mg def I keep seeing.

What is a good ratio of Ca/Mg to use? I've been using a CalMag (0.3 ml/L) additive throughout the grow; is it necessary? Would epsom salts added periodically be better instead?

Any comments welcome, Cheers
 
G

Guest

3:1 is a good ratio. Seedlings should get about 50mg/l calcium...and then you raise it over the life of the plants to 100mg/l for a medium size plant and 5th week of flower roughly 150mg/l. But all this depends on your lights a bit too. If you got crazy ones u can even go higher as the plants will take up more
 
OakyJoe

OakyJoe

OGJoe / Wiener und kein Allemann
Veteran
Guest said:
3:1 is a good ratio. Seedlings should get about 50mg/l calcium...and then you raise it over the life of the plants to 100mg/l for a medium size plant and 5th week of flower roughly 150mg/l. But all this depends on your lights a bit too. If you got crazy ones u can even go higher as the plants will take up more
Click to expand...

3:1 is the way to go as you said, i give 120ca/40mg or 150ca/50mg ( mg per L ) and they love it!
 
f-e

f-e

Well-known member
Mentor
Veteran
Drinking water reports can be misleading. Telling us of calcium present, but it forms plants don't use. Even when presented as calcium oxide, it often isn't calcium oxide. It seems telling us the oxide equivalent is a common legal practice. I'm in the UK where feed bottles must tell us calcium oxide. Nothing else is required, just calcium as an oxide equivalent. They don't tell you it's an equivalent though. They just state the calcium oxide present, as if it's a fact. When in fact, it's not true.

Calcium can be present in so many forms, that just knowing the quantity, doesn't really relate to what the plants get. This has left many papers claiming the calcium in tap is available, and many claiming its not. Both sides have it wrong, because from the minute 'go' they didn't identify the calcium compounds in their tests. Which is never all calcium oxide as it's not water soluble in an real concentration. Most will likely be calcium carbonate in harder areas. Not available in that form, but can be made available by changing it. Nitric acid is of use here. It can fully disperse (disassociate) in solution, and burn off carbon. Phosphoric can't disassociate as fully, so does about half the job of nitric.


While a drinking water report can tell you 100 calciums, you shouldn't expect to get them to use as plant nutrients.



3:1 is a traditional choice. I find myself wanting more Mg than that, and lowering K and Ca to get the Mg in there has been my only route to minimal satisfaction. It follows that if your Mg is low, that adding calmag keeps it low. Or rather, the same distance behind calcium, which pushes Mg out. Thus.. pointless. The 3 must compete. Also adding P helps Mg.
 
G

Guest

CAL/MAG 2:1. Lower light, no co2 3:1. Coco requires more mag in my experience with a high light co2 room. Same room in rockwool or media with similar cat ion exchange is fine with 3:1 for most strains.
 
TwistedPistil

TwistedPistil

Member
f-e said:
3:1 is a traditional choice. I find myself wanting more Mg than that, and lowering K and Ca to get the Mg in there has been my only route to minimal satisfaction. It follows that if your Mg is low, that adding calmag keeps it low. Or rather, the same distance behind calcium, which pushes Mg out. Thus.. pointless. The 3 must compete. Also adding P helps Mg.
Click to expand...

This is interesting.

what are ideal K/Ca/Mg ratios in for coco in your opinion?
 
f-e

f-e

Well-known member
Mentor
Veteran
A typical K:Ca ratio puts K around double that of Ca, but many people mixing their own feeds are putting in more Ca than K. In coco you have K in abundance. I have moved out of coco simply because of it's addition of K and Na. The coco I get is grown in salty areas, but I literally just read that the US market gets a lot from down south, that's not grown by the sea. What's certainly true, is the number of Ca deficiency issue's people see, and the total absence of K deficiency threads. I would go for 1:1 in the feed, and keep in mind that is still more like 2:1 in the substrate, maybe higher. Canna are the coco people, and their feed is more like 1:2 so 1:1 really is a fair starting point for your coco grow.

I'm using Ca:Mg at 3:2 by using a 3:1 calmag and Epsom. I need the sulphur of the Epsom, not just the Mg. Sulphates help keep coco clean, by shifting the K and Na out. I also see sulphur deficiencies that are recognised in professional publications, but are not typically seen on our charts. Where the bottom leaves are effected. Leaves getting lighter, and mottled, before turning yellow, but not light yellow. A bold yellow.

The ratio's are golden, but only if you are reading old books. All we need in that triangle, are enough of each individually, and a total that's not poison. Our plants are very good at finding what they need. Your target EC comes into play though, as you don't want over 100ppm of Mg. Some tests have played with it alone, and found 70ppm the upper limit before it's more harm than good. Jacks is about 90ppm I read yesterday.

After chewing this over for a while, 2:2:1 or of you have better control, 150:200:80 might be a better starting point. It's impossible to say really, it's just a starting point. We do have a number of feed choices that work as perfectly good bases though. I will site Jacks as a good example. Cheap powder that offers easy Ca and Mg adjustment. Though I believe the K is excessive, lots of peeps use it. Bill Farthing has his cheap nutrients thread that's revolving around Jacks in coco mainly.
 
TwistedPistil

TwistedPistil

Member
f-e said:
A typical K:Ca ratio puts K around double that of Ca, but many people mixing their own feeds are putting in more Ca than K. In coco you have K in abundance. I have moved out of coco simply because of it's addition of K and Na. The coco I get is grown in salty areas, but I literally just read that the US market gets a lot from down south, that's not grown by the sea. What's certainly true, is the number of Ca deficiency issue's people see, and the total absence of K deficiency threads. I would go for 1:1 in the feed, and keep in mind that is still more like 2:1 in the substrate, maybe higher. Canna are the coco people, and their feed is more like 1:2 so 1:1 really is a fair starting point for your coco grow.

I'm using Ca:Mg at 3:2 by using a 3:1 calmag and Epsom. I need the sulphur of the Epsom, not just the Mg. Sulphates help keep coco clean, by shifting the K and Na out. I also see sulphur deficiencies that are recognised in professional publications, but are not typically seen on our charts. Where the bottom leaves are effected. Leaves getting lighter, and mottled, before turning yellow, but not light yellow. A bold yellow.

The ratio's are golden, but only if you are reading old books. All we need in that triangle, are enough of each individually, and a total that's not poison. Our plants are very good at finding what they need. Your target EC comes into play though, as you don't want over 100ppm of Mg. Some tests have played with it alone, and found 70ppm the upper limit before it's more harm than good. Jacks is about 90ppm I read yesterday.

After chewing this over for a while, 2:2:1 or of you have better control, 150:200:80 might be a better starting point. It's impossible to say really, it's just a starting point. We do have a number of feed choices that work as perfectly good bases though. I will site Jacks as a good example. Cheap powder that offers easy Ca and Mg adjustment. Though I believe the K is excessive, lots of peeps use it. Bill Farthing has his cheap nutrients thread that's revolving around Jacks in coco mainly.
Click to expand...

Again, thank you, sir! As always.

I'm trying to prepare this sealed room with LEDs and co2. I'm anticipating the need to make adjustments to my old 6/9 profiles. Cal nit and mag sulfur will be in my handy dandy deficiencies drawer. Probably some cal carbonate too. I've been delving into Jack's 321 and 4/2 ratios, and they seem more suited for straight hydro than coco. But people have had success with them in coco, I just can't adequately measure what their definition of success is. So I'm trying to wrap my head around several concepts at once, while trying to dodge the sea of misinformation that is all too widespread on the internet.

I will look into this Bill Farthing fellow. Thank you for the input, sir.
 
f-e

f-e

Well-known member
Mentor
Veteran
No problem at all good sir.
I read the heads thread here, and in my mind his adjustment was needed because the coco has so much K. However the P reduction it bought looked a bit drastic. This was covered on the first page or two. He doesn't talk about the K but rather Ca availability he couldn't achieve. I'm reading between the lines, suspecting it was K at fault.

We don't hear much about that now. It's pretty much Jacks or Masterblend for most people. Which one, comes down to your location. Biologist was posting about the Jacks this week. He strayed from the course, spent time and money, and came back to Jacks. It sounds like it grows brick weed with good numbers.
 
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