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grizzman_gw

Source of Phosphorus and Calcium

grizzman
15 years ago

Anybody know a good chemical source for soluble phosphorus?

I found a product called liquid phosphorus, but I believe it is basically phosphoric acid, probably diluted a bit.

I've also found monopotassium phophate and dipotassium phosphate. the difference here is an extra potassium molecule in the di and an extra hydrogen molecule in the mono.

do you all know what their difference is as it pertains to the plants?

Also, how much potassium would I need in my solution before it has detrimental effects on my plants?(or somehow binds my calcium)

How about a good source of soluble calcium. I already have calcium nitrate, but later in the plants cycle, I'll want to reduce the nitrogen levels, which will also reduce my calcium levels

Thanks!

PS: I'm not looking for a slice two bananas and ferment in mineral spirits kind of answer here. I want to be able to know how much I'm adding by weighing it with a scale or a graduated cylinder.

Comments (16)

  • wordwiz
    15 years ago

    A simple way - crush up a couple of multi-vitamins and add that to your water. I use DWC and just drop two of them into the water each week.

    Mike

  • greystoke
    15 years ago

    A good source of liquid phosphate is Ca(H2PO4)2, which you get by letting triple-super-phosphate soak in water. The calcium dihydrophosphate dissolves readily in the water to a maximum concentration of 1.8%. The super-phosphate is about 75% soluble in water.

    I get soluble calcium by dissolving sea shells in vinegar. Let ±50g of shells soak in 1 liter of white vinegar. After about 24 hours you can boil the lot in a stainless steel pot for about an hour. Then filter the liquid (I use a coffee filter [LOL]) to remove the excess of shells and make-up the volume to 1 litre.
    This way you obtain a calcium acetate solution that contains 15 grams of calcium per litre.

  • danielfp
    15 years ago

    The best source of calcium and phosphate you can find is Ca(H2PO4)2 which would be called calcium dihydrogen phosphate (in chemistry) and more often simple superfosfate or calcium monophosphate in agriculture.

    The difference between the different forms of phosphate, PO4(-3), HPO4(-2) and H2PO4(-1) is just their protonation state. The molecules present in your solution change as a function of pH with the ionic forms HPO4(-2) and H2PO4(-1) being present predominantly at the regular working pH in hydroponics (5.5-6.5). You can add whatever one of those phosphate species you like and it will change into the right one when you adjust the pH.

    However, if you add a salt with H2PO4(-1) and one with HPO4(-2) you will create a buffer effect because of one being the conjugate base of the other. That is another way to buffer the pH of a nutrient solution, although at a higher pH (near 7).

    Here is a link that might be useful: Everything Hydroponics

  • hooked_on_ponics
    15 years ago

    Hey grizz, I'm curious what you're doing with this.

    Why not just use something that's mixed to the proportions you want ahead of time?

  • gringojay
    15 years ago

    Hi greystoke,
    ? Would your vinegar Ca extraction work out the same with chicken egg shells as the raw material ?

  • greystoke
    15 years ago

    Hi gringojay,
    I haven't tried that, but I'm certain it will work. (You'll need a few eggs though (LOL))

  • gringojay
    15 years ago

    Hi greystoke,
    ? Are you able to estimate the grams of Ca that egg shells , substituted for sea shells, would yield in your formulation ?
    (The egg shell in vinegar extract, for soluble calcium, was told me by an old country doctor over a quarter of a century ago for use as a human nutritional supplement of calcium.)

  • greystoke
    15 years ago

    It would be the same.
    The amount of calcium(Ca) that will dissolve as acetate in 1L of white vinegar (5%) - irrespective of its source - is ±15g (in theory: 16.7g).
    Just dissolve egg shells untill they no longer dissolve.

  • gringojay
    15 years ago

    Here's another use for egg shells.
    Poke a hole in the egg shell, collect edible contents that drain out & then slip the shell's opening over a cactus spike. Apply many of these on one entry way plant & it watch visitors try to figure out what you are growing.

  • bilberrybrian
    15 years ago

    Check out the book "Hydroponics, A practical guide for the soilless grower" by J. Benton Jones

    ISBN 1-884015-32-8

    It's targeted more at commercial growers than hobbyists but that's the level you should be aiming for it sounds like. There is a good amount of information about different salts that are used for nutrients. I have the book checked out from MSU right now for sources of phosphorus and it lists:

    Ammonium Phopshate (mono/di/tri)
    Potassium Phosphate
    Phosphoric Acid

    but there are a few more like calcium phosphate that aren't listed for whatever reason.

  • grizzman
    Original Author
    15 years ago

    Hooked on Ponics, the reason I'm doing this is I am basically creating a custom mix from a few sources and currently my phosphorus is lower than the recipe I'm basing this on. It may not be a problem initially, but I'd like to be able to somewhat adjust that level independent of my primary nutrient formula. Also, as bloom set begins, I'd like to be able to reduce the amount of nitrogen in the formula. since my primary source of calcium in calcium nitrate, to reduce the nitrogen would also reduce the calcium. Therefore I need something that will also or additionally allow me to be able to adjust the calcium levels. Ideally, I'd prefer them independent of each other, but I have to work within reasonable funds and what's available. I can get liquid phosphorus which is basically diluted phosphoric acid or monopotassium phosphate. I haven't found an independent source of calcium though. and then I hit upon, and as others have mentioned, calcium phosphate.
    Wait a minute, I believe I'm restating my initial post?!? anywho, that's basically why. I want better control of my nutrient solution.

  • greystoke
    15 years ago

    That's precicely what I'm doing.
    I measure about 80g of triple-super-phosphate and let it soak in a 2L soda bottle for a few days. (I keep a few of these bottles on the shelf) I siphon-off the clear top layer and use that as a 1.8% concentrated (=saturated)Ca(H2PO4)2 solution.
    When the plants mature, I measure the PO4 content with an aquarium testkit, and I supplement it with the Ca-phosphate solution. (Beware! It's very acid, so you may need to adjust the pH aferwards)

  • grizzman
    Original Author
    15 years ago

    Greystoke
    when making the calcium acetate, is boiling required? and what does that part do? I was thinking of just dumping egg shells and vinegar into a glass bottle then skimming liquid off the top as needed as a calcium supplement. since the concentraition will always be 15ppm, the idea is just get as much as required for the concentration I want to make up.

    Also, regarding the triple super phosphate you said:
    "A good source of liquid phosphate is Ca(H2PO4)2, which you get by letting triple-super-phosphate soak in water. The calcium dihydrophosphate dissolves readily in the water to a maximum concentration of 1.8%. The super-phosphate is about 75% soluble in water."
    I am a bit confused by the discrepencies in your percentages. are you saying 1.8% of the solution is Calcium Dihydrophosphate and the remaining 73.2% are just filler?
    Thanks for the assistance.

  • greystoke
    15 years ago

    grizzman wrote: I was thinking of just dumping egg shells and vinegar into a glass bottle then skimming liquid off the top as needed . . .

    I suppose that could work. The boiling is intended to remove any residual acid. Maybe you should test the pH to make sure(?)

    Triple-super-phophate:
    Is about 75% soluble. The soluble component is mono-calcium orthophosphate. The rest is calcium sulphate (I think). But mono-calcium orthophosphate only dissolves in water up to a percentage of 1.8%.

  • grizzman
    Original Author
    15 years ago

    Thanks for the clarification.

    so the triple super phosphate will actually give a much larger percentage of calcium as the remainder of the soluble product is calcium sulphate? and the available phosphate will be the percentage of the 1.8% of mono-calcium orthophosphate?

    thanks again!

  • jamesvlad
    13 years ago

    Hello there! I hope I´m not too late.
    Plants can only absorb soluble calcium, and the eggshells are Calcium Carbonate that is very insoluble. So it´s better to buy some cheap Calcium Carbonate than using eggshells. But you have to disolve Calcium Carbonate. Wait!! there´s a little secret.
    Easy! Just add to Calcium Carbonate some water and Citric Acid. Citric Acid complex calcium and eliminates carbonate (CO2), and it´s a very acid with buffer capacity. ;-)
    How much you may ask? That´s your work!
    Then you can safely add potasium phosphate as phosphorus source.