Over on TPT, a member made a comment about the gluconate form of Ca having a larger molecule than, perhaps, other Ca salts. The implication seems to have been that the larger molecule somehow affects Ca uptake by plants.
It is almost 3x the molar mass of gypsom(CaSO4).
Yes a more complex molecule.C12H22CaO14
Does it break down as easily and available for plant uptake?
Don't know if the carbon in it would be available for plants either.
As far as dosing is concerned, you do need about 3x the amount of Ca gluc to match that needed for CaSO4. However, the Ca gluc is much more soluble, making it much easier to mix-up in small containers.
Calcium gluconate is also listed as a phosphate binder, would this affect macro nutrients? CaHPO4 formation?
Also no real solubility data that I've found, just listed as slowly???
At least CaSO4 has a listed solubility.
Ca, is Ca. The atomic mass of Ca is 40.078 and no matter what the molecule is made of , the Atomic mass remains same.
Gluconate is a complex which keeps the Ca bound but not as strongly as chelates.
Calcium has strong affinity to a lot of chelates.
Most likely what’s happening is as soon as the Gluconate complex is broken, any chelate available within water might be tying up the Ca. This is just a hypothesis but only further analysis can confirm.
Actually plants easily take up Gluconate as such because it’s a carbon complex (sugar) which plants do uptake (the idea behind excel).
Thanks @rajkm. You confirmed what I thought about the Ca being Ca, regardless of how it's presented. I've also seen debates over NO3 being different than NO3, which also never made sense.
So, any binding (which was not my initial concern), is simply due to the 'bad' chelates introduced from our micros, be it EDTA, DTPA HEEDTA, etc. In my case, that's even less of a concern because I mix my own traces and use Fe gluc.
Your statements raise a different concern, though. With the Ca being made available much more quickly from the gluconate separation, maybe it would be better (although probably not noticeable) to add a small amount of Ca gluc daily, along with my Fe gluc and other traces, rather than front loading it in my RODI water weekly. Just looking for a 'best practice' approach and thinking out loud. Do you see any problem putting Fe gluc and Ca gluc into a dosing solution long term (months)?