Calcium Supplementation

[gonewild]

OK. Science nerd warning:

Just how "readily available" is Ca from oyster shell? It's not the most soluble material known to mankind.

Once you put it in the pot it is 100% readily available! At that point it is up to the plant to use it or not. oke:

You are right Ray the calcium won't instantly dissolve even from the flour size particles and the flour particles will actually was through the media and out the drainage holes.

I am thinking that many plants like paphs and phrags get a great deal of benefit from having their roots actually in contact with calcium containing materials like limestone or oyster shell. I know P.kovachii does. I think the roots actually take calcium directly from the media more efficiently than absorbing dissolved calcium in the water. For that reason now I mix the oyster shell into the media. When the oyster shell has all dissolved away it is time to repot.

 

[Erythrone]

I didn't mean that oyster shell was very soluble, Ray! Excuse me, I speak French. Traduction of my ideas is not always easy.

I agree that oyster shell does not instantly dissolve (nor « traditional » lime that is applied on top of fields in agriculture or on maple forest "floor" here when the soil is too acidic or when there is Calcium deficiency in the ecosystem).

Oyster shell is mainly composed of calcium carbonate, no ? Calcium carbonate is not very soluble in water, but there are more Ca++ in solution when the solution is more acidic, isn't it ? If I remember what I learned at school, roots plants acidify soil (H+). I suppose that calcium carbonate in the mix can dissolve a little more at the root « level »... Of course, calcium leaching is a reality too...

But if calcium carbonate dissolve slowly, I supposed that adding oyster shells to our mixex can have a rather long effect.

 

[Rick]

Once you put it in the pot it is 100% readily available! At that point it is up to the plant to use it or not. oke:

You are right Ray the calcium won't instantly dissolve even from the flour size particles and the flour particles will actually was through the media and out the drainage holes.

I am thinking that many plants like paphs and phrags get a great deal of benefit from having their roots actually in contact with calcium containing materials like limestone or oyster shell. I know P.kovachii does. I think the roots actually take calcium directly from the media more efficiently than absorbing dissolved calcium in the water. For that reason now I mix the oyster shell into the media. When the oyster shell has all dissolved away it is time to repot.

A ways back when this question first came up on this site, I took a spoonful of rinsed oyster shell, stuck it in a bottle of distilled water, shook it every now and then for a day or so, and then took it in the lab. I found that it raised the pH almost to 9.0 and got quite a noticeable amount of hardness out of it (i.e dissolved Ca and Mg). In a potting mix with bacteria, fungus, roots and various micro niches (the rhizosphere) that are primarily acidic, I bet the rate of oyster shell decomposition can be much faster. I think one of the bigger benefits of adding oyster shell, limestone, or bone meal is for pH control and keeping the mix "sweeter" over longer periods of time than you would achieve without it. Most of the nutrients that plants want are most available in that 5.5 to 6.5 s.u. range.

 

[Rick]

I just tried looking at this from a "plants are plants' aspect for an alternate view.

I looked up the mineral composition of seawater:

Sodium = 10,800ppm
Potassium = 392ppm
Calcium = 411ppm
Magnesium = 1290ppm (3X the amount of Ca on a weight basis, 5X the molar equivalents.)

Then I looked at the mineral composition of Kelp (a marine plant):
Sodium = 3,700mg
Potassium = 13,000mg
Calcium = 1,000mg (25 molar eq)
Magnesium = 610mg (25 molar eq) (i.e. 1:1 Ca to Mg ratio)

From the Antec site looking at the relative number of atoms of each metal for orchids:
Sodium = not listed
Potassium = 250,000
Calcium = 125,000
Magnesium = 80,000 (i.e. 1.56:1 Ca to Mg ratio)

At least for K, Ca, and Mg, there is quite a bit of similarity between Kelp growing in hydroponically overloaded magnesium rich mixture and orchids typically grown with more calcium available than magnesium. However one should note the growth rate of kelp is way higher than for orchids.

In chemical and many biological systems, Ca can be antagonistic to Mg, so at this time I'd avoid lopsiding the amount of Ca in the environment around my orchids much beyond a 2:1 by weight ratio. Most surface, well, and tap waters already have much more Ca than Mg. So I'm finding that the more I use oyster shell or bonemeal, the more Epsom salts I need to balance it out.

 

[Rick]

Maybe we should consider dolomite rather than oyster shell.

It's about 50/50 CaO/MgO

 

[gonewild]

Maybe we should consider dolomite rather than oyster shell.

It's about 50/50 CaO/MgO

I would much prefer dolomite over oyster shell.

I have tried to find crushed dolomite but can't find a source, at least not on the west coast. Plenty of powder and even pelletized but not crushed rock dolomite or even limestone. Powder or little pellets degrades too fast in the media.

I did once do a side by side test with oyster shell and crushed limestone. (had to crush it myself, never again!)
I mixed different ratios of both shell and limestone into the media from 10% up to 100% and grew Phrag seedlings for 1 year. I concluded that there was no visible difference in growth results between the shell or limestone. The percentage in the mix did not make a difference except ....

The addition of shell or limestone increased growth at all percentages except
100% oyster shell reduced growth whereas 100% limestone did not. But I think this was a result of the flat shape of the shells as compared to the chunky limestone causing a poor media environment.

Two points to consider about the above are that most of the seedlings were P.kovachii which likely need a higher pH and all the pots got daily irrigation with an MSU fertilizer solution with added Mg so there was flushing of the free water in the media.

 

[Rick]

I found that there is a dolomite quarry in TN (but not near me or very accesable). Several local Coops have different grades of pelletized lime or dolomitic lime with varying amounts of Mg, but only Morton's Supply in McMinville, TN said they had "dolomite". $5 pe 50lb. probably cost $50 in slow boat shipping to the west coast.

Also check out some aquarium stores. I saw a company that was packaging crushed dolomite for African Cichlids, and we used to get it for salt water aquarium gravel when I was in Calif.

Did you use RO water for your experiment? SOCal tap water probably has lots of ca and mg in it to start with.

 

[Paphman910]

What about crushed Coral that they sell in fish aquarium shops?

Paphman910

 

[gonewild]

I found that there is a dolomite quarry in TN (but not near me or very accesable). Several local Coops have different grades of pelletized lime or dolomitic lime with varying amounts of Mg, but only Morton's Supply in McMinville, TN said they had "dolomite". $5 pe 50lb. probably cost $50 in slow boat shipping to the west coast.

Also check out some aquarium stores. I saw a company that was packaging crushed dolomite for African Cichlids, and we used to get it for salt water aquarium gravel when I was in Calif.

Did you use RO water for your experiment? SOCal tap water probably has lots of ca and mg in it to start with.

Yes, RO water. Most tap water in CA is toxic. RO water to mix the MSU and RO water when ever I want plain water. Even RO water through the auto mist system.

Is the 50# bag from Morton crushed like gravel or pulverized like sand? The aquarium stores around here only have crushed coral for gravel. They say it is from fossil sources but I don't know what the sodium content might be.
So I just use the oyster shell from the feed store across the street and it works. But still if I had the option I would use dolomite gravel.

 

[gonewild]

What about crushed Coral that they sell in fish aquarium shops?

Paphman910

Just mentioned that in my last post after you posted this.
I am not sure about possible sodium content of the coral. If the coral is actually from fossil deposits the sodium may all be leached out but maybe not?

 

[Eric Muehlbauer]

There was a thread about this a year or 2 ago. Apparently the crushed coral is very good, no salts. I tried a bag of it...there were no problems. Right now, I'm using Espoma pelletized dolomite. Again, no problems. I also used to put marble chunks on the bottom of my parvi and brachy pots, so that the roots would be touching the rock. Not sure it did anything better than would have been without the rock.

 

[Erythrone]

Interesting.... I never thought about crushed coral!!! Here it is easy to buy many kind of lime.

For Marble: it is a metamorphic rock, derived from sedimentary calcarous rock. But it does not react like lime. They simply don't have the same properties.

I remember that marble doesn't react with acid (no bubbles!!! If we add acid on calcarous sedimentary rock, there is a strong reaction. But no reaction with marble. This is a method for identifying rocks) Can marble be useful in our mixes?

 

[Eric Muehlbauer]

Metamorphism shouldn't change the chemical characteristics of a rock. In the earth science classes I've taught, I always used HCL as a test for marble as well as limestone, and it reacted. However, I believe that marble can be derived from dolomite also, and I haven't found dolomite to react as well to HCL. It may not react at all. That said, I have heard, maybe because of its density, that marble isn't as good as limestone. However, whenever I see people using marble mulch over azaleas and rhododendrons (an unfortunately common sight in my neighborhood) the shrubs are always chlorotic, so it must have some effect on soil pH.

 

[Rick]

Interesting.... I never thought about crushed coral!!! Here it is easy to buy many kind of lime.

For Marble: it is a metamorphic rock, derived from sedimentary calcarous rock. But it does not react like lime. They simply don't have the same properties.

I remember that marble doesn't react with acid (no bubbles!!! If we add acid on calcarous sedimentary rock, there is a strong reaction. But no reaction with marble. This is a method for identifying rocks) Can marble be useful in our mixes?

Marble has virtually no buffering capacity. As you noticed it doesn't react to acid and it's very hard. That's why it makes great counter tops.

I don't know what the magnesium composition is of crushed coral. And the magnesium composition of dolomitic limestone can be from 5-20%. Pure dolomite is 50/50 CaO/MgO. So getting lime or dolomitic lime from the COOPS maybe a real crap shoot as to how much magnesium is in the bag.

I couldn't get a straight answer from Morton's as to whether they were selling straight dolomite or dolomitic limestone, but it is "pelletized" so I'm assuming the grain size to be at least a couple millimeters.

 

[Ray]

Pelletized lime and dolomite are often just powder that is bound by water-soluble polymeric materials. It is intended to provide for easy broadcast on lawns, then in rapidly breaks down into powder so it can go to work.

I'd be wary of using it, for fear of a sudden release.

 

[Erythrone]

Marble has virtually no buffering capacity. As you noticed it doesn't react to acid and it's very hard. That's why it makes great counter tops.

So I am not crazy?

 

[gonewild]

This is not the best place to ask if you are crazy. :rollhappy:

Good to know that the crushed coral does not have sodium content.

I think marble would be something like using a ceramic. It is composed of minerals but a heat process has altered the availability of the minerals to plants and the environment.

Marble does not dissolve or easily break down in a moist environment so it would not provide what we are looking for in limestone.

Dolomite pellets break down too fast so they don't offer a long term source of minerals in the root zone.

The small size of dolomite pellets does not give much surface area for a root to be in contact with.

 

[Rick]

Pelletized lime and dolomite are often just powder that is bound by water-soluble polymeric materials. It is intended to provide for easy broadcast on lawns, then in rapidly breaks down into powder so it can go to work.

I'd be wary of using it, for fear of a sudden release.

I just picked up a $4 bag of the EPSOMA Garden Lime

It's made from dolomitic limestone and has a
guaranteed analysis of 21% Ca and 10% Mg

As carbonate minerals it looks pretty close to straight dolomite of 52% calcium carbonate, and 35% Mag carbonate (still a bit shy on Mag).

It is pelletized, and from my test on the kitchen counter it looks like it will break down into a fine sand/silt after a short time in water (as Ray said).

But it looks like it will go a long ways with an application of around 5 lbs per 100 sqft to maintain a pH of about 6.5

On the directions is says 2-4 tbspoons per plant, but I don't know if this comes out at the same dose as the above.

I just did some converting and came up with about 2.5gr per 4" pot.

 

[Rick]

2.5 gr came out to 1/4 to 1/2 tspn.

I also put 2.5 gr into 50ml water and measured pH (came out to 10.3).

So if you use it then I would only use it for acidic mixes and sparingly.

I'm also still trying to get some real dolomite, but so far I've only come across some expensive ($16/L without shipping) from a specialty aquarium supply.

 

[Ray]

Rick, check local Petco and Petsmart stores. I have purchased dolomite aquarium substrate from them. It's great for African cichlids.

I purchased a bag of dolomitic limestone yesterday - again in the roughly 3:2 Ca:Mg ratio, but why is that bad? My understanding is that while plants need both, they don't need them equally, making me think that 3:2 is still probably overkill on the Mg.