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Help with Calcium and Phosphorus Relation

V

voidpainter

Hi, I'm looking for a simple explanation as to how Calcium and Phosphorus interact in these particular examples of a soil mix and plant symptoms.


THE MIX: loaded with soft rock phosphate, calcium carbonate and high P bat guano. After "cooking" it was sitting at 6.8pH.


Plant A: visible phosphorus deficiency on middle leaves + purple petioles + purple stems.


I read somewhere that high Ca and high P in alkaline soils tend to react and lock each other out. I'm looking for more info regarding what actually happens here and how would one solubilize them again into readily available forms.

Plant B: visible zinc deficiency, limeish colored top leaves, shorter plants than the control group, less yield, smaller flowers.


This suggests the P levels in that particular pot were high which in turn lead to a Zn lockout. Or Zn was locked out due to high pH.


both pots of the Plant A and Plant B measured 6.9 - 7.1 pH at harvest.



............

Given that the two pots in question started in the same soil mix,example A lead to a reaction between Ca and P which made P unavailable & example B lead to Zn lockout due to high P and/or higher soil pH



Is it then possible that the same cause (eg. high P or high pH) leads to different scenarios, different issues?


Both plants were "identical" clones and both plants were grown in same soil mix.
 
P

paradoxlost

Member
phosphate is minimally soluble in almost all soil, not just alkaline. Actually at a neutral pH phosphorus is insoluble. In fact, I would imagine all that P is probably binding up calcium, which is than binding up phosphorus. I would get some Sulphur and humic acid into the mix to solubilize the P. Also get some mychorrizal fungi into the mix, as that will help the plant get the P without affecting the pH, as 6.8 is solid actually. Also you should foliar P to address the lock out.
 
G.O. Joe

G.O. Joe

Well-known member
Veteran
There's lots of insoluble phosphates and you're making them. Plants might be fine with things like P, Mg, and Ca in particular insoluble forms - if there's enough in the soil - but only if the pH is in the area where the insolubility is reversible, since some acid is required for that to happen. Soluble P tends to be leached out anyways since plants don't absorb P well compared to N. Maybe it's best to have semi-insoluble phosphates so they don't react with the metals. The chemistry of metals like Cu, Fe, Mn, and Zn in mixtures of everything else that might be in soil gets complicated in neutral solutions, all kinds of things should precipitate and it may be more difficult to reverse the insolubility.
 
G.O. Joe

G.O. Joe

Well-known member
Veteran
I grew a lot in promix at 5.5-6 and that was fine, for sure 7 is high for metals and no one pH is right for everything, but 6 is pretty close.
 
V

voidpainter

Makes sense about P and metals, thanks.



Yet I'm sceptical about 6 being "close" to right. I bet it works on some or maybe most strains but experience goes against the "claim" in this case. Since I made trials with both ends of the spectrum (~6.0 and ~7.0) my unsubstantiated recommendation would be to aim for the range of 6.3 - 6.6 pH.


Aiming for ~6.0 pH brought about Ca, Mg and K uptake problems with sensitive plants.


Aiming for ~7.0 pH brought about Zn, P, Fe problems with sensitive plants.


Of course I also had plants that didn't mind what the pH was, whether 6, 5.8 or 7.1.



As regarding foliar, I sprayed all the zinc in the world and nothing changed for the plant with Zn problems. Foliars when soil pH was whacked didn't produce a change for me, sadly. Might for others tho, I don't know.
 
P

paradoxlost

Member
If you add mychorrizal fungi and humic acids this should make semi soluble P and icnrease the ability of hte plant to uptake it. Thats the "hack" natures has found. Humic acid increases the surface area of CaPO4 and FePO4 by like 3000%
 
Rico Swazi

Rico Swazi

Active member
voidpainter said:
Hi, I'm looking for a simple explanation as to how Calcium and Phosphorus interact in these particular examples of a soil mix and plant symptoms.

THE MIX: loaded with soft rock phosphate, calcium carbonate and high P bat guano. After "cooking" it was sitting at 6.8pH.
Click to expand...


possibly overloaded? a little clay goes a long way IMO and personally would use one or the other but not both
I'm looking for more info regarding what actually happens here and how would one solubilize them again into readily available forms.
Click to expand...
healthy soil comprising of organic matter and micro-organisms, including mycorrhizae will be your best bet to ' solubilize them again into readily available forms' in a process called mineralization


temperature, moisture and as stated above, microbial life will greatly affect uptake as much as pH and should be considered part of the equation


good luck
 
V

voidpainter

Yeah it was overloaded as fuck on purpose and the microbial life couldn’t manage it in one cycle from clone to harvest. The mix was inoculated with LAB, had a good amount of quality OM and dozens different mycorrhizae. These beasts can only do what they can do, sadly they’re not magical haha.
 
Rico Swazi

Rico Swazi

Active member
I believe high P is bad for mycorrhizae, no?
the magic is these plants survive some of the crazy things done to them
my main point being you made no mention of temperature when testing for pH

Rico Swazi said:
temperature, moisture and as stated above, microbial life will greatly affect uptake as much as pH and should be considered part of the equation

good luck
Click to expand...




high or low temps cause deficiencies also
 
Last edited:
Creeperpark

Creeperpark

Well-known member
Mentor
Veteran
Solubilize them with acid in the water and nutrients will be available. For a micro boost, use 5.5 pH water and raise it a little for cal-and mag boost. I always run the intake water in the fives. Some plants in the 7+ ph would show iron chlorosis.
 
4

40degsouth

Well-known member
Hi everyone, l hope you’re all well!!
Some really great advice but l think we’re all missing the piece of the puzzle that is, what is the volume of soil that we’re dealing with; let’s start there....and watering.....and temperatures.
Cheers,
40.
 
Rico Swazi

Rico Swazi

Active member
Yeah 40, fresh out of frozen fish so hoping this will work in the meantime :bashhead: :biggrin:

I believe we are saying the same thing that without strict protocols, there is little chance of determining cause and effect



I also believe Joe was on the right track earlier saying the OP is making a insoluble precipitate (apatite ?) with the addition of so much phosphate.





G.O. Joe said:
There's lots of insoluble phosphates and you're making them. Plants might be fine with things like P, Mg, and Ca in particular insoluble forms - if there's enough in the soil - but only if the pH is in the area where the insolubility is reversible, since some acid is required for that to happen. Soluble P tends to be leached out anyways since plants don't absorb P well compared to N. Maybe it's best to have semi-insoluble phosphates so they don't react with the metals. The chemistry of metals like Cu, Fe, Mn, and Zn in mixtures of everything else that might be in soil gets complicated in neutral solutions, all kinds of things should precipitate and it may be more difficult to reverse the insolubility.
Click to expand...
 
4

40degsouth

Well-known member
Ouch, ouch, ouch....Rico:bigeye:
It’s difficult to diagnose but l think the clues are the lockouts. I’ve also found that treating the symptoms can lead to one chasing one’s tail around the garden.
I believe the problem lies with the ph and perhaps the volume of soil is to small to buffer effectively. I personally aim for 6.5.
Low soil temperatures will also lock out phosphorus and mychorrizal fungi will become “lazy” and dormant in soils with a high phosphorus footprint. We also need to remember that there’s only three or four species that live in symbiosis with cannabis roots.
Cheers,
40.
 
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