Ca:mg Ratios. Where Did It Start And How Important Is It?

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MGRox

MGRox

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If you look around you can find all sorts of information about proper Ca:Mg ratios. You will also find that there are a few common ratios that are in literature as well, but where did this concept come from and how important is this for us?

The first conjecture at a "proper" Ca:Mg ratio came about in 1901 while looking at total Ca and Mg levels. The results here, suggested a ratio of 5:4 Ca:Mg.

Next, there was further research done in 1945. By this time, researchers had realized that total and exchangeable Ca and Mg levels were different and now considered exchangeable the more important factor.
From this, they determined the "proper" ratios of Ca:Mg based on CEC and saturation percentages.
They resulted in a saturation of; 65% Ca, 10% Mg, 5% K and 20% H. From this they determined that the "proper" ratios of Ca:Mg was 6.5:1 Ca:Mg.

As time passed and further research was conducted; suggestions of "proper" Ca:Mg ratios seemed to land at or between 5:1 and 8:1 Ca:Mg.

To add to this confusion, there are several other areas of research that have suggested a 3:1 Ca:Mg ratio.

Why would there be such a large difference in Ca:Mg ratio between various sources? Simple, they are both the SAME as they are stated from different perspectives.
I.E. 3 mmol of Ca = 60 ppm and 1 mmol of Mg = 12 ppm.
Here, you can see that a 3:1 ratio IN mmol of Ca:Mg is the SAME as a 5:1 ratio IN ppms.

So, now that we know where this came from and what "proper" ratios are; how does this effect productivity or growth then? For this we need to look into Ag and soils where Ca:Mg ratios are not kept specific; yet productivity or yield is tightly tracked.

Here are some links specific to this:
http://www.ipm.iastate.edu/ipm/icm/2003/4-21-2003/camg.html



From the first link:
""The results strongly suggest that for maximum crop yields, emphasis should be placed on providing sufficient, but nonexcesive levels of each basic cation rather than attempting to attain a favorable basic cation saturation ratio (BCSR), which evidently does not exist." Various greenhouse and field trials indicate that crop productivity is not influenced by ranges from less than 1:1 to more than 25:1--ratios outside of what is normally measured in soils.
....
"In summary, the Ca:Mg ratio concept is unproven and should not be used as a basis for fertilization or liming practices. Having sufficient levels of Ca and Mg is the proper method of evaluation, rather than trying to manipulate ratios."


From the second link:
"Thus, if adequate levels of calcium and magnesium are present in the soil, variations in the Ca:Mg ratio between 2 and 8 have no effect on yield, and varying the calcium saturation percentage from 32% to 68% and magnesium from 35% to 12% also do not influence yield.
.......
"Thus, the amounts of these nutrients taken up are determined by the selectivity of the roots. The remainder accumulates in the immediate vicinity of the roots. Therefore, it is doubtful that the supply of calcium and magnesium to the root surfaces would ever be limiting under Wisconsin conditions where soil pH is maintained in good growing range. The Ca:Mg ratio seldom will be the dominant factor determining calcium and magnesium uptake by plants. This was shown by the small variations in the tissue Ca:Mg ratio when the soil Ca:Mg ratio was varied


And from the third link:
"The optimum soil cation ratio concept, developed about 50 years ago, has been incorporated into some fertilizer recommendation philosophies in various ways. Recent field evaluations of this concept, however, show that the ratio of cations has no impact on the response of crops to Ca, Mg, and K in fertilizer programs. The optimum cation ratio concept has a major disadvantage in that even if the ratio of cations in the soil is considered to be optimum, a nutrient deficiency may still exist. A sufficient supply of available cations in the root zone is the most important consideration in making economic fertilizer recommendations."

The above papers also give results for yields in various ratios of Ca to Mg that go considerably outside any of the proposed ratios without crop production loss.

The last quote is probably the best takeaway in that sufficient levels in soils of each element is more important than their ratios to each other.

Happy Farmin'
 
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kuz

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So you are saying it just doesnt matter? lol. Been thinking that a lot lately, the plants do well with a wide range of nutrients. Coco gives me problems if I dont add calcium every time they get watered. I keep the ca/mg ratio close to 1 to 1, ppms, no clue about mmols.

How does one nutrient lockout another? I thought that is what was important about the ratio's. My plants have been really sensitive about calcium
P1015448.JPG
every since I switched to coco. Maybe it is because I am giving them too much mg? I just gave these tea made with dechlorinated tap water for a couple of days, and have some issues. I thought there would be enough ca in the tap water. The two matilda's are clones and the yeti is from seed. Yeti doesnt have the yellowing in the leaves but doesnt look really healthy either. They all get fed from the same reservoir.

I think i am going back to dirt, supersoil, true living organics, whatever.
 
seaslug

seaslug

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"In summary, the Ca:Mg ratio concept is unproven and should not be used as a basis for fertilization or liming practices. Having sufficient levels of Ca and Mg is the proper method of evaluation, rather than trying to manipulate ratios."

Sounds good to me. A common "stoner" ratio seems to be 2:1, Ca to Mg. GH MaxiGro is 3:1 and MaxiBloom is 1.4:1, I believe.
 
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MGRox

MGRox

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@seaslug yea, the maxigrow is 3:1 but the bloom is 1.42:1 (after checking), whereas the Flora Nova Bloom is 2:1

@kuz Well, mainly I was just providing some background on the ratios and such. With Ca/Mg ratios; this is a great case where a visual identification is the best to determine your course. If you see Ca-, then increase the Ca; if you see Mg- then increase that; without "worrying" about the ratio between the two, necessarily.

There are many variables that could affect what the best Ca/Mg would be for a specific single plant even; Variations in CEC, clay content, watering method and frequency, light, growth stage etc. So there probably won't ever be an optimal "one-size fits-all" Ca/Mg I guess.

Specifically here though, MJ is often provided with higher levels of Ca and Mg (also closer Ca:Mg ratios) than is typical with other crops or agriculture. The common notion may be that MJ uses / needs more calcium and magnesium than other plant types. However, if one compares plants that survive in low Ca, Mg , N or P environments; it is not that these require less elements for a similar production, but that they have a higher "use efficiency" than other plants.
The fact that MJ tends to require more Ca and Mg than in many other plants relates to it being "less efficient" at uptaking / utilizing these elements. So, if a particular geno/pheno -type seems to require more Mg; it also is less efficient as opposed to actually needing more.


(NOTE)
I tend to try and find understandings with all this stuff and look for how various aspects were arrived at. So, quite often I'll take from accepted theories (say high P in bloom) and try to figure out where this came from and how it's all related. I suppose that's where this came about too. To me, I often convey stuff like this more as data rather than some great epiphany or something. Though I like figuring this all out and where it came from; it is not likely to ever yield some massive change to things. All of this (if I bring up techy stuff) , i guess, is maybe to help with perspective / understanding or for those that might find some interest in it.
 
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FooDoo

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Awesome thread!

I have been researching this for the last week.

I'm running 5ml calmag, 5ml GH micro and 10 ml GH bloom which gives me

109n 66p 114k 63mg 30s 126ca

Its a 2:1 ratio of ca:mg. Plants look amazing but I noticed a few spots pop up. @Seamaiden was awesome enough to point out it was calcium def.

IMG_20150204_225437592_HDR.jpg


IMG_20150204_225835914_HDR.jpg


So I'll be stepping it up to 3:1 ratio.

This thread was a good start to answering a lot of questions for me https://www.icmag.com/ic/showthread.php?t=181405

From that thread they posted

"With ideal VPD comes high uptake of Ca and B, due to consistently ideal rate of transpiration"

So I think lower 1.5:1 and 2:1 ratios work better when vpd isn't ideal, but when the room is dialed in, you gotta go higher till your girls tell you they reached the sweet spot

"1. in terms of Ca to Mg ratio, anywhere from 1.5-8 is fine, the claim that there is an ideal Ca to Mg ratio (i.e. 3) is a total myth. I debunked that myth over at TCC and I could post many studies here if anyone is interested." -spurr
 
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kuz

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MGRox. Really interesting how you figured out the ratios were the same, just different measurements (mmols vs ppms). I need to look at the links you posted, always curious where these ratios came from.

Foodoo. Not sure about the terminology, as I understand it, ca and b can only travel through the sap channel, the rest of the nutrients can also move through the cells by transpiration. When it gets too hot and dry the sap stops flowing, i have seen it so bad that it caused a ca deficiency. I thought the guy probably had root aphids or something, no bugs ever found. I think it was lack of ca caused by the poor environment.

Fresh Starts. I thought it was a ca deficiency. I had extra tea so instead of just once, thats all I gave the plants for three days. Anyway, a little bit of calcium nitrate seemed to fix it. New growth is good and the lower leaves are not getting any worse. The k is pretty light and probably giving them too much mg. Thats why I am posting here. Seen enough info that I believe I would be better off cutting back the mg.
 
MGRox

MGRox

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One of the way's that I've "visualized" things in regards to elements; is with those rooms full of playground colored balls. Of course, there are many factors involved that make this "Actually" more complex; though the visualization seems to apply as a generalization.

So, if you have a pool full of these colored balls and let's assume that each color represents a specific element. (I.E. Yellow for N, blue for P, white for Ca, etc etc). Now then, take a similar "ratio" of these elements in your nutrient solution and apply them to these colored balls. For instance, since were on Ca:Mg; let's throw in 3 parts Ca (white) balls and 1 part Mg balls. Do this for all the elements in your mix, or well just kind of imagine these colors in ratios.

Now, Jump into this pool! Okay now, look around you at any ball that is touching your body / legs. What colors are touching and how many of each color? In this example, you are the root of a plant that just happened to grow into a section of soil (also applies for mass flow). The balance of your various elements are going to primarily determine the "likely-hood" of you coming into contact with each element. So, if a proportion of one element is too high in relation to another (or others); a deficiency can arise from a perspective of "rarity for encounter" vs other negative factors (precipitation, soil binding, moisture etc).

The above would apply more directly to a 0 CEC soil, with continual moisture supply vs any situation with CEC or interval watering. When we introduce CEC and / or "organics"; then these components alter the "rarity for encounter" via binding elements based on charge / reactivity, to the medium particles. A similar situation still does apply with CEC, but that here; its' more about altering "saturation" ratios as opposed to a "rarity of encounter" that would come about from only considering "mass flow" delivery.

So in higher CEC's and soil; there is a balance (more so with cations) based on saturations and affinity to saturate elements. This will predominate the necessity of a particular Ca:Mg (or other elements) here in regards to retention. In 0 CEC environments, the ratio will be more based around the encounter chance and "the now high" CEC of roots vs medium.

The above is considered outside of precipitation, ph fluctuation, temperature and solubility affects.

sorry to ramble a bit here, but thought maybe this could help with perspective on things too. :D
 
Fresh Starts

Fresh Starts

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I meant 1tsp per liter epsom for foliar not in rez BTW @kuz

Calcium nitrate foliar is not so good. Probably has a ammoniacal nitrogen. Might green the plant up but that's not Ca or N deficient

Using JPH?
 
N

nightmarecreature

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Its most definitely strain dependent. OGs like to be hit hard with Cal/Mag. Non OGs really dont use much. If you are running any type of OG, I would start at 5ml minimum every feeding and lower your K in coco. Im using 4ml of Cal/Mag every feed right now.

Another thing is that purple stems are not normal. Even in OGs, they should be pure green. If they are purple, they might look healthy, but something is lacking. Ive been working with them long enough to know.
 
Seamaiden

Seamaiden

Living dead girl
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I meant 1tsp per liter epsom for foliar not in rez BTW @kuz

Calcium nitrate foliar is not so good. Probably has a ammoniacal nitrogen. Might green the plant up but that's not Ca or N deficient

Using JPH?
I don't think it would have ammoniacal N because the N is in the form of NO3 (nitrate nitrogen).

Also, someone mentioned that Ca and B can only be transported through the "sap channel" (not sure what that means). I don't know about B being available via foliar application, but I know that most non-bound forms of Ca are (not bound to CO3, CO3 is a problematic molecule).
 
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FooDoo

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OGs like to be hit hard with Cal/Mag.

Ca and mg need to stop being grouped together.

Calcium is almost always the culprit and not so much mg. There's people that have run 30-40 ppm TOPS of mg with their ogs and never shown a def.

Just because the label on your bottle reads calmag, doesn't mean its now all of a sudden one element and you cant say one without the other.
 
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kuz

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I don't think it would have ammoniacal N because the N is in the form of NO3 (nitrate nitrogen).

Also, someone mentioned that Ca and B can only be transported through the "sap channel" (not sure what that means). I don't know about B being available via foliar application, but I know that most non-bound forms of Ca are (not bound to CO3, CO3 is a problematic molecule).
I cant find what I was reading, where I got that. Didnt really understand it all anyway. lol. Something unique about the way calcium moves though the plant. But I dont think that it had anything to do with ca /mg ratios anyway.

If you get vpd dialed in will you need more calcium, or less because the plant is operating more efficient. I never thought about marijuana needing more ca/mg because they are less efficient than other plants. That kind of changes my perspective.
 
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kuz

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Xylem sap. mg and ca move within the xylem through ion exchange. or maybe not, idk. I dont want to study cell biology for the next couple of months to try and figure it out. Cant find a good simple answer, I get the idea its not fully understood.

Maybe when rate of transpiration is high, more ca is needed because the uptake of other nutrients is increased.
 
MGRox

MGRox

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Ca movement in the plant you say? *grins*

*reaches into his bag of papers*



Here's about as much as you'll probably ever want to know about Ca uptake / movement in plants. There is a ton of good information in the paper, though it opens a couple doors that I've not yet wanted to open publicly.

First though I can quote some goodies for Ca uptake / movement / regulation.

"Calcium is taken up by roots from the soil solution and delivered to the shoot via the xylem. It may traverse the root either through the cytoplasm of cells linked by plasmodesmata (the symplast) or through the spaces between cells (the apoplast). The relative contributions of the apoplastic and symplastic pathways to the delivery of Ca to the xylem are unknown (White, 2001). However, the movement of Ca through these pathways must be finely balanced to allow root cells to signal using cytosolic Ca2+ concentration ([Ca2+]cyt), control the rate of Ca delivery to the xylem, and prevent the accumulation of toxic cations in the shoot."

"Calcium deficiency is rare in nature, but may occur on soils with low base saturation and/or high levels of acidic deposition (McLaughlin and Wimmer, 1999). By contrast, several costly Ca‐deficiency disorders occur in horticulture (Fig. 1; Shear, 1975). These generally arise when sufficient Ca is momentarily unavailable to developing tissues. Deficiency symptoms are observed (a) in young expanding leaves, such as in ‘tipburn’ of leafy vegetables, (b) in enclosed tissues, such as in ‘brown heart’ of leafy vegetables or ‘black heart’ of celery, or (c) in tissues fed principally by the phloem rather than the xylem, such as in ‘blossom end rot’ of watermelon, pepper and tomato fruit, ‘bitter pit’ of apples and ‘empty pod’ in peanut. They occur because Ca cannot be mobilized from older tissues and redistributed via the phloem. This forces the developing tissues to rely on the immediate supply of Ca in the xylem, which is dependent on transpiration. Transpiration is low in young leaves, in enclosed tissues and in fruit."


--Just these couple things are very good tid bits of info. First, that Cystolic Ca is used as an internal signal and regulator. Second, that Ca- issues generally are seen when Ca cannot be delivered fast enough rather than necessarily being deficient. As well it connects @kuz reference to Ca, xylem and transpiration. However note, that the primary affected areas are also low in transpiration and as such would not benefit as much. Also, is the consideration of increasing transpiration and stomatal closure (not listed above); could also be a counter as well and, i suppose, further is a Cystolic Ca linked "stress response".

A bit more in depth look at uptake and movement then;

"Calcium is acquired from the soil solution by the root system and translocated to the shoot via the xylem."........"The delivery of Ca to the xylem is restricted to the extreme root tip and to regions in which lateral roots are being initiated"......In these regions a contiguous, Casparian band between endodermal cells is absent or disrupted, and/or the endodermal cells surrounding the stele are unsuberized. The Casparian band restricts the apoplastic movement of solutes and suberization prevents Ca2+ influx to endodermal cells. These observations suggest that Ca might reach the xylem solely via the apoplast in regions where the Casparian band is absent or disrupted, or circumvent the Casparian band by entering the cytoplasm of unsuberized endodermal cells when the Casparian band is present. These are referred to as the apoplastic and symplastic pathways, respectively."

"Each pathway of Ca movement across the root confers distinct advantages and disadvantages. The apoplastic pathway allows Ca to be delivered to the xylem without impacting on the use of [Ca2+]cyt for intracellular signalling. Intracellular signalling requires [Ca2+]cyt to be maintained at submicromolar levels in the resting cell and to increase rapidly in response to developmental cues or environmental challenges. Since the Ca2+ fluxes required for [Ca2+]cyt signalling are minute compared with those required for adequate nutrition, both these requirements for [Ca2+]cyt signalling might be compromised by high nutritional Ca2+ fluxes through root cells. However, the Ca flux to the xylem through the apoplastic pathway is influenced markedly by transpiration, which could lead to vagaries in the amount of Ca supplied to the shoot and the development of Ca disorders. Furthermore, the apoplastic pathway is relatively non‐selective between divalent cations , and its presence could result in the accumulation of toxic solutes in the shoot. By contrast, the symplastic pathway allows the plant to control the rate and selectivity of Ca transport to the shoot. It is thought that Ca2+ enters the cytoplasm of endodermal cells through Ca2+‐permeable channels on the cortical side of the Casparian band, and that Ca2+ is pumped from the symplast by the plasma membrane Ca2+‐ATPases or Ca2+/H+‐antiporters of cells within the stele. By regulating the expression and activity of these transporters, Ca could be delivered selectively to the xylem at a rate consistent with the requirements of the shoot."



On Xylem sap and cytosol concentrations / regulation;

"The Ca concentration in xylem sap ([Ca]xylem) is influenced greatly by [Ca2+]ext, and [Ca]xylem between 300 µm and 16·5 mm has been reported. The relative proportion of Ca2+ to total Ca also varies, with organic acids, such as malate and citrate, chelating Ca2+ in the xylem sap. When abundant Ca is present in the xylem sap, there is a close relationship between Ca distribution to the shoot and transpiration. Within the leaf, Ca follows the apoplastic route of the transpiration stream and accumulates in either the mesophyll cells, trichomes or epidermal cells adjacent to guard cells, depending on the plant species. Both the [Ca2+]cyt in guard cells and the closing of stomata in detached epidermal strips are sensitive to apoplastic Ca2+ concentrations within the range of [Ca2+]xylem."

"The removal of Ca2+ from the cytosol against its electrochemical gradient to either the apoplast or to intracellular organelles requires energized, ‘active’ transport. This is catalysed by Ca2+‐ATPases and H+/Ca2+‐antiporters. By removing Ca2+ from the cytosol these enzymes perform several important functions: (1) they maintain a low [Ca2+]cyt in the resting (unstimulated) cell appropriate for cytoplasmic metabolism; (2) they restore [Ca2+]cyt to resting levels following a [Ca2+]cyt perturbation, thereby influencing the magnitude, kinetics and subcellular location of [Ca2+]cyt signals; (3) they replenish intracellular and extracellular Ca2+ stores for subsequent [Ca2+]cyt signals and permit the generation of local [Ca2+]cyt oscillations through their interplay with Ca2+ channels; (4) they provide Ca2+ in the ER for the secretory system to function; (5) they remove divalent cations, such as Mg2+, Mn2+, Ni2+ or Zn2+, from the cytosol, to support the specialized biochemistry of particular organelles and to prevent mineral toxicities."


Cystolic Ca and signaling;

"The [Ca2+]cyt of plant cells increases in response to many developmental cues and environmental challenges (Table 2 w/ link). This is considered essential for producing a physiological response. It is thought that elevating [Ca2+]cyt is a primitive, and universal, response to stress. Sanders et al. (1999) observed that the low solubility product of Ca2+ and phosphate would have necessitated a [Ca2+]cyt lower than the [Ca2+] of seawater to maintain energy metabolism. They presumed that this required the early evolution of mechanisms to remove Ca2+ from the cytoplasm, and noted that a homeostatically maintained submicromolar [Ca2+]cyt would have been ideal for the subsequent evolution of [Ca2+]cyt signalling systems, since it would confer sensitivity and speed to any signal. Sanders et al. (1999) also noted that the chemistry of Ca2+, which can coordinate six to eight uncharged oxygen atoms, had fortuitously made possible the evolution of proteins that change conformation upon binding Ca2+, allowing the cellular perception and transduction of a [Ca2+]cyt signal."

---Take the time to browse over Table 2 link there. It shows Cystolic responses of Ca as a result of various stressors. There are many "Key" things in that table, for instance Red light and a permanent increase in [Ca]cys (this connects to PSI PSII photoinhibition rant I did xD).
---Also, take note of the larger font size and underlined sentence above. I.E. that plants likely first evolved the ability to regulate Ca out of necessity and connected to seawater concentrations. This was kind of a "mind blown" moment for me back when I read this.

The paper continues more in depth with these cystolic signals and is pretty interesting, but not needed here. Hopefully the above should cover the most key points with Ca movement, uptake and signaling.

Finally, there is mention of a point; not yet covered (pandoras box) and maybe it would be best to propose it as a question. First, from the paper;

"Ecologists have classified plant species into calcifuges, which occur on acid soils with low Ca, and calcicoles, which occur on calcareous soils. The Ca concentrations in calcifuge and calcicole plants growing in their natural habitats differ markedly. However, it is the ability to tolerate excessive Al, Mn and Fe that largely determines the flora of acid soils, and an insensitivity to Fe‐ and P‐deficiencies that determines the flora of calcareous soils. Nevertheless, calcifuges generally grow well at low Ca2+ concentrations in the rhizosphere ([Ca2+]ext) and respond little to increased [Ca2+]ext, which may even inhibit growth (Fig. 2). Conversely, the mechanisms that enable calcicole plants to maintain low [Ca2+]cyt in their natural habitat are believed to restrict their growth at low [Ca2+]ext by inducing Ca‐deficiency."

For the moment.....What does everyone think that Cannabis falls into here? Calcifuge or Calcicole? :D
 
MGRox

MGRox

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Wow, I gotta read this a few more times.
But I think genetics play a role here.

Well with this, in so far as to try and separate indica from sativa there may be some tiny variations, yes. Outside of this, a genetic variation would be more noticeable with close neighbors (I.e. strawberry, tobacco)
The paper above only mentions the Calcifuge / Calcicole thing and doesn't go into a bunch of detail about it. However, the one section shown does provide a lot of key info.

So the question still stands then.......Calcicole or Calcifuge?
 
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