# Magnesium absorption



## consettbay2003 (Aug 31, 2012)

How readily is magnesium absorbed through paph leaves?


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## Stone (Sep 1, 2012)

consettbay2003 said:


> How readily is magnesium absorbed through paph leaves?



As mag.sulphate, very readily. But you want to have your Ca at least double your Mg. and it goes in through the roots.


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## Mocchaccino (Sep 1, 2012)

Stone said:


> As mag.sulphate, very readily. But you want to have your Ca at least double your Mg. and it goes in through the roots.



Stone, I have Epsom Salts in my hands. I remember someone in a thread shared the amount of Epsom to be included in waterings but I could not find that. So I'm just going to ask how much I should add. Perhaps 0.1 g in 10L of water? 
And which Calcium compound should I use. I only got Calcium carbonate. I know it's rather insoluble.


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## Rick (Sep 1, 2012)

Stone said:


> As mag.sulphate, very readily. But you want to have your Ca at least double your Mg. and it goes in through the roots.



Agreed!

We start to see some weird stuff when plants are chronically exposed to magnesium levels higher than Ca.

Unless you are using RO or rain water, your typical surface or ground waters will have 2 to 10 times as much Ca to Mg. So adding very small amounts of Mg into your tap water can be very beneficial bringing the balance closer to 2:1. But without knowing the hardness of your water, and the ratio of Ca/Mg in it, its impossible to say how much epsom salt to add on a regular basis.


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## Rick (Sep 1, 2012)

Mocchaccino said:


> Stone, I have Epsom Salts in my hands. I remember someone in a thread shared the amount of Epsom to be included in waterings but I could not find that. So I'm just going to ask how much I should add. Perhaps 0.1 g in 10L of water?
> And which Calcium compound should I use. I only got Calcium carbonate. I know it's rather insoluble.



Calcium sulfate (gypsum) is much more soluble than CaCO3, and should also be readily available.

Calcium chloride and Calcium nitrate are more soluble yet, but I don't like the idea of having that much chloride around the roots, and the nitrate needs to take into account any other nitrogen fertilizer you are using.


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## Stone (Sep 1, 2012)

Yes I'm using a lot of gypsum now. I got a sack of it and used a very fine sieve to filter out all the course particles (1 to 4mm) and use about 1/3 teaspoon of these on a 4'' pot. This will supply Ca and S for many months without interfering with pH too much.
The Mg in your usual fertilizer should supply plenty of Mg.
If not try about 20 mg/L along with 100 mg/L Calcium sulphate. Or 1/2 of both of these.
As Rick mentioned, too much Mg as foliar feed might cause imbalance with Ca, especially if the roots are damaged. And don't forget B.
If you cant find Calnitrate or Gypsum, you could try a drench of Calcium Hydroxide ( builders lime ) every 3 months or so and use a fertilizer with a higher percentage of Ammonium or Urea. Its a balacing act but I find its always safer to dilute so much it seems ridiculous. Maybe 10 times what the manufacturer recommends, and work from there.


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## Eric Muehlbauer (Sep 1, 2012)

Calcium hydroxide is also called picking lime and kalkwasser (for reefkeepers), but its pretty caustic stuff. I'm assuming any of it used on orchids must be extremely dilute.


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## Rick (Sep 2, 2012)

Eric Muehlbauer said:


> Calcium hydroxide is also called picking lime and kalkwasser (for reefkeepers), but its pretty caustic stuff. I'm assuming any of it used on orchids must be extremely dilute.



Eric

Don't you still use some of that EPSOMA peletized lime now and then.

It's powdered dolomitic lime that has close to a 50/50 ratio of Ca/Mg, and is kind of a fast release way of adding Ca/Mg to a pot. It will yank the pH around like other lime products.


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## Eric Muehlbauer (Sep 2, 2012)

I don't use Espoma anymore. I never had any problems with it, but I picked up a 15lb bag of crushed coral which I mix with my bark for some of my paphs. More stable, doesn't turn into gray paste, and I can add some to my son's fish tank to help maintain the pH. I still have a bag of Espoma, but I use it on my lawn in Cutchogue, where the soil is highly acidic. I realize that the crushed coral is probably not necessary, as I use Orchiata bark and high Ca low K fertilizer, but I feel it can't hurt.


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## Stone (Sep 2, 2012)

Eric Muehlbauer said:


> Calcium hydroxide is also called picking lime and kalkwasser (for reefkeepers), but its pretty caustic stuff. I'm assuming any of it used on orchids must be extremely dilute.



Isn't that quicklime (calcium oxide)?


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## consettbay2003 (Sep 2, 2012)

How much (in tsps.) calcium nitrate and magnesium suiphate would you need to add to a gallon of RO water to maintain the 2:1 cal/mag ratio?


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## Stone (Sep 2, 2012)

consettbay2003 said:


> How much (in tsps.) calcium nitrate and magnesium suiphate would you need to add to a gallon of RO water to maintain the 2:1 cal/mag ratio?



0.59 g/L Calcium nitrate gives you 100ppm Ca.
1.01 g/L Magnesium sulphate gives you 100ppm Mg
So 0.505 g/L mag sulphate and 0.59 Cal nitrate will give you 2:1 and you can go up or down as you please.
You can add that to 1 Lt or 10 gallons and you still have your 2:1 but obviously not 100ppm.
I think 3 or 4:1 is still fine.


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## Rick (Sep 2, 2012)

Stone said:


> 0.59 g/L Calcium nitrate gives you 100ppm Ca.
> 1.01 g/L Magnesium sulphate gives you 100ppm Mg
> So 0.505 g/L mag sulphate and 0.59 Cal nitrate will give you 2:1 and you can go up or down as you please.
> You can add that to 1 Lt or 10 gallons and you still have your 2:1 but obviously not 100ppm.
> I think 3 or 4:1 is still fine.



I take it the mag sulfate you are calculating from is Epsom salt (half the weight is from waters of hydration).

Also to note that 0.59g/L of Ca(NO3)2 -4H20 yields 70mg/L NO3-N, so not much reason to add a bunch more other fertilizer for N.

Since conversion from liters to gallons = X 3.785 (roughly 4 times) if you want to use these absolute numbers to up or down your recipe.


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## Rick (Sep 2, 2012)

Stone said:


> 0.59 g/L Calcium nitrate gives you 100ppm Ca.
> 1.01 g/L Magnesium sulphate gives you 100ppm Mg
> So 0.505 g/L mag sulphate and 0.59 Cal nitrate will give you 2:1 and you can go up or down as you please.
> You can add that to 1 Lt or 10 gallons and you still have your 2:1 but obviously not 100ppm.
> I think 3 or 4:1 is still fine.



I take it the mag sulfate you are calculating from is Epsom salt (half the weight is from waters of hydration).

Also to note that 0.59g/L of Ca(NO3)2 -4H20 yields 70mg/L NO3-N, so not much reason to add a bunch more other fertilizer for N.

Since conversion from liters to gallons = X 3.785 (roughly 4 times) if you want to use these absolute numbers to up or down your recipe.

And then if you want to build from scratch you could add 0.035g/L of monopotassium phosphate to get about 10 mg/L K, and about 15 mg/L phosphate


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## Eric Muehlbauer (Sep 2, 2012)

Calcium hydroxide isn't quicklime....but a solution of it is sometimes called limewater.


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## Stone (Sep 3, 2012)

Eric Muehlbauer said:


> Calcium hydroxide isn't quicklime....but a solution of it is sometimes called limewater.



Calcium oxide.
http://en.wikipedia.org/wiki/Calcium_oxide


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