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are coco nutes necessary?
- Thread starter captinknots
- Start date
C
Carl Carlson
As the article that Spurr posted explains, the CEC exists, but not as a buffer of nutrients for the plant or against a change in pH. Ca deficiencies show up because the coco has not been charged with enough Calcium and is still stealing it, so to speak, from the plant.
D
dramamine
D
dramamine
and this one:
Carl explained the charging hypothesis well, however, that is something I am have some doubts about...
I never charged coco, I just made sure I water with near-full strength ferts with at least 75 ppm Ca. It would seem to me charging media isn't needed because it is achieved during the first fertigation if sufficient Ca is present (along with K, Mg, etc., to increase percent base saturation). Because the CEC of coco does not hold Ca well, the soil solution should have Ca in equilibrium (or close to it) to the Ca in held at CEC sites. Ca at CEC sites should easily separate from the CEC sites (and become plant available) via. acidic ions exudates by roots, other cations and pH of rhizosphere and soil solution.
That is why I do not charge coco, and I never seen Ca deficiency. Maybe if people don't provide enough Ca with the first watering (and all consecutive watering) they could see Ca deficiency. However, I think that is the exception, not to the rule (re: the observation some people notice when young plants in coco can seem to have Ca deficiency).
The main reason I do not agree with the idea that the CEC of coco means it needs to get charged, is that s.peat has both higher CEC and higher bulk density than coco, yet there are no such Ca deficiency issues with s.peat. My point is if there is Ca deficiency due to CEC in solless media we would see it in s.peat too, and s.peat would be worse because it has higher CEC and bulk density. Thus, I don't think the CEC of coco is the reason for people noticing Ca deficiencies.
S.peat is mixed with dry dolomitic lime and sometimes calcitic lime, and when whetted some cations will be freed. Those freed cations of Ca and Mg would take up some CEC sites and increase percent base saturation, but I doubt by much right away. Thus I still think the comparison of young plant in fresh Promix BX (without nutrient charge) to a young plant in Bonticare Cocogrow (without nutrient charge) is valid. In that, peat will have higher CEC and greater bulk density, yet when both plants are given the same fertilizer (containing all the cations and anions) it's the plant in coco than can exhibit Ca deficiency. To me that speaks volumes about what might, and might not be causing the Ca deficiency some people notice in coco.
Coco and s.peat share similar physical properties. The biggest difference I have found (besides s.peat hydrophobic nature) is a higher Perched Water Table in peat and when roots are young (with lower biomass) this can mean increased access to low tension water (i.e. easily used by roots). Also coco has a higher rate of "evapotranspiration", this means water held in coco is evaporated more quickly than water held in peat, and would mean higher soil-water status with lower water tension in peat for a greater time period. In both cases peat moss would provide higher soil-water status with and lower water tension, i.e., more easily 'accessed' and 'used' water, that should mean increased Ca uptake by roots in s.peat vs. Ca uptake by roots in coco via. increased soil-water status (R. J. Dunham and P. H. Nye, 1976) and lowered water tension. Those factors could be a reason Ca deficiency can be found in some young plant in coco and not in s.peat.
A few nutrients deficiencies can look like others sometimes, ex. calcium deficiency can look like magnesium deficiency [1][2].
In terms of uptake of magnesium it has been found Ca hinders uptake of Mg when Ca is in high concentration esp. vs. concentration of Mg. The higher the Ca vs. Mg the greater the Ca hinders uptake of Mg. The level of Ca to Mg (when Ca is in high concentration) that have been shown to hinder Mg uptake are 10:1 (Ca:Mg) to 20:1 an greater (B. Jacoby,1961; David P. Moore, Roy Overstreet, and Louis Jascobsom, 1961).
Because the observed Ca deficiency seems to affect mostly young plants, I think the problem is related to the water and xylem movement from media thorough plant (that is affected by soil-water status and water tension). Young plants transpire less well than mature plants, and transpiration is the major reason Ca and boron are able to come from soil to leaf (Bill Argo and Paul Fisher, January 2008). Ca moves fairly slowly within plant xylem, the speed is affected by rate of transpiration.
Most ions do not not rely upon 'suction' of roots (from taking in water) to pass into the root, but Ca and boron do (Bill Argo and Paul Fisher, January 2008). So if the roots are not 'sucking up' water to a sufficient degree there could be a lack of Ca moving into the root and through the xylem into the leafs. And if the rate of transpiration is not high enough the Ca will move more slowly to sink tissue (leafs). Not only that, but Ca is slowly moved into roots even at sufficient rate of transpiration, Ca is known to be "slow", while other ions are not (R. J. Dunham and P. H. Nye, 1976). Ca is poorly mobile inside plant tissue so older leafs can't give younger leaf their Ca very well at all (unlike what happens with nitrogen). All of those facts contribute to Ca movement into leaf, and thus contribute to Ca deficiency in leaf.
Rate of transpiration controls intake of water by roots (and thus Ca) and movement of water - xylem (and thus Ca) into leaf. The lower the rate of transpiration the lower the uptake water (and thus uptake of Ca) and movement into leaf. Environmental conditions that affect rate of transpiration are mostly those that affect stomatal conductance (openness of stoma). Some examples are low RH, medium RH and high temp, high RH and low temp, high irradiance, low soil-water status (how dry the media is), light spectrum (blue light opens stoma, but red light closes stoma and green light would close stoma but in the presence-and-after blue light) and air movement.
The environmental conditions with the biggest affect upon stomatal conductance is RH-canopy temp, along with low soil-water status (dry media) and high irradiance (lots of light).
What I am trying to write is: (1) I don't think CEC is the culprit in terms of Ca deficiency in young plant in fresh coco because the same deficiency isn't seen in s.peat. Considering that s.peat has higher CEC and normally higher bulk density; and (2) I think the reason for Ca deficiency in mostly young plants in fresh coco is in large part due to rate of transpiration, soil-water status and water tension; and (3) the rate of transpiration is affected by a few environmental factors that reduce stomatal conductance; thus (4) depending upon the growers' specific environment she/he might or might not observe Ca deficiency when using the same coco, containers, ferts, water and clone as someone who did observe Ca deficiency in an different environment (ex. less-bright light, lower RH, or poor watering skills); finally, (5) if a grower does not flush fresh coco before use, and said coco was not well flushed by the manufacture, the coco would in essence be pre-charged with K and Na (at least), both of which will take up CEC sites, thus increasing percent base saturation (from K) translating into less potential CEC sites for Ca or Mg, meaning greater levels of Ca and Mg in soil solution and rhizosphere that can lead to increased Ca and Mg uptake; that could another factor why some coco growers experience Ca deficiency and some do not.
YMMV, this is only my opinion
References:
[1] "Symptoms of Deficiency In Essential Minerals"
Wade Berry, UCLA
A Companion to Plant Physiology, Fourth Edition by Lincoln Taiz and Eduardo Zeiger
http://4e.plantphys.net/article.php?ch=3&id=289
[2] "Marijuana Garden Saver: AKA The Complete guide to Sick Plants,pH, and Pest troubles!"
https://www.icmag.com/ic/showthread.php?t=11688
"Uptake of magnesium & its interaction with calcium in excised barley roots 1,2"
David P. Moore,3 Roy Overstreet, and Louis Jacobson
Plant Physiol. 1961 May; 36(3): 290–295
"Calcium-magnesium ratios in the root medium as related to magnesium uptake by citrus seedlings"
B. Jacoby
Plant and Soil
Volume 15, Number 1, 74-80
"The Influence of Soil Water Content on the Uptake of Ions by Roots. III. Phosphate, Potassium, Calcium and Magnesium Uptake and Concentration Gradients in Soil"
R. J. Dunham and P. H. Nye
Journal of Applied Ecology
Vol. 13, No. 3 (Dec., 1976), pp. 967-984
"Understanding Plant Nutrition: An Introduction"
Bill Argo and Paul Fisher, January 2008)
http://www.greenhousegrower.com/magazine/?storyid=109
No, I don't consider well flushed coco to be inert, but it should have noticeably reduced EC and reduce the percent base saturation (K cations filling CEC sites) vs. coco not flushed at all.
The pH of the water used to flush has a large effect upon releasing (dissociating) cations from CEC sites. Hydrogen ions (H+) are able to dissociate cations (including K, Ca, Mg, etc.) from CEC sites, allowing them to the be more easily flushed away. So if we use phosphoric acid (pH down) in water lowering pH we will be increasing flush CEC sites.
This is how roots are able to release cations from CEC, they release not only acidic protons (H+ ions) as exudates (ex. when taking in ammoniacal N), but they also create carbonic acid (Co2+water) in media that releases H+ ions, etc.
D
dramamine
Hey, thanks for the thoughts.
Carl explained the charging hypothesis well, however, that is something I am have some doubts about...
I never charged coco, I just made sure I water with near-full strength ferts with at least 75 ppm Ca. It would seem to me charging media isn't needed because it is achieved during the first fertigation if sufficient Ca is present (along with K, Mg, etc., to increase percent base saturation). Because the CEC of coco does not hold Ca well, the soil solution should have Ca in equilibrium (or close to it) to the Ca in held at CEC sites. Ca at CEC sites should easily separate from the CEC sites (and become plant available) via. acidic ions exudates by roots, other cations and pH of rhizosphere and soil solution.
When you say soil solution, I think you're referring to the nutrient solution...hope that's right. If these cation exchange sites need Ca in equilibrium with solution given, the coco will indeed "steal" Ca from solution, making less available to the plant. Initially, at least. This is the standard explanation. If this is what you are saying, then a lot depends upon the practical CEC of the coco. This seems contrary to what you have previously posted.
That is why I do not charge coco, and I never seen Ca deficiency. Maybe if people don't provide enough Ca with the first watering (and all consecutive watering) they could see Ca deficiency. However, I think that is the exception, not to the rule (re: the observation some people notice when young plants in coco can seem to have Ca deficiency).
The main reason I do not agree with the idea that the CEC of coco means it needs to get charged, is that s.peat has both higher CEC and higher bulk density than coco, yet there are no such Ca deficiency issues with s.peat. My point is if there is Ca deficiency due to CEC in solless media we would see it in s.peat too, and s.peat would be worse because it has higher CEC and bulk density. Thus, I don't think the CEC of coco is the reason for people noticing Ca deficiencies.
S.peat is mixed with dry dolomitic lime and sometimes calcitic lime, and when whetted some cations will be freed. Those freed cations of Ca and Mg would take up some CEC sites and increase percent base saturation, but I doubt by much right away. Thus I still think the comparison of young plant in fresh Promix BX (without nutrient charge) to a young plant in Bonticare Cocogrow (without nutrient charge) is valid. In that, peat will have higher CEC and greater bulk density, yet when both plants are given the same fertilizer (containing all the cations and anions) it's the plant in coco than can exhibit Ca deficiency. To me that speaks volumes about what might, and might not be causing the Ca deficiency some people notice in coco.
Coco and s.peat share similar physical properties. The biggest difference I have found (besides s.peat hydrophobic nature) is a higher Perched Water Table in peat and when roots are young (with lower biomass) this can mean increased access to low tension water (i.e. easily used by roots). Also coco has a higher rate of "evapotranspiration", this means water held in coco is evaporated more quickly than water held in peat, and would mean higher soil-water status with lower water tension in peat for a greater time period. In both cases peat moss would provide lower soil-water status with and lower water tension, i.e., more easily 'accessed' and 'used' water, that should mean increased Ca uptake by roots in s.peat vs. Ca uptake by roots in coco via. increased soil-water status (R. J. Dunham and P. H. Nye, 1976) and lowered water tension. This is also be a reason Ca deficiency can be found in some young plant in coco and not in s.peat.
I'm having trouble with the idea that a higher Perched Water Table could mean anything but a less developed root system, hence less access to water (low tension or not). Also, it seems the deficiencies occur even with frequent watering (drip system,etc.), so soil-water status seems not to play into it.
A few nutrients deficiencies can look like others sometimes, ex. calcium deficiency can look like magnesium deficiency [1][2].
Because the observed Ca deficiency seems to affect mostly young plants, I think the problem is related to the water and xylem movement from media thorough plant. Young plants transpire less well than mature plants, and transpiration is the major reason Ca and boron are able to come from soil to leaf (Bill Argo and Paul Fisher, January 2008). Ca moves fairly slowly within plant xylem, the speed is affected by rate of transpiration.
Most ions do not not rely upon 'suction' of roots (from taking in water) to pass into the root, but Ca and boron do (Bill Argo and Paul Fisher, January 2008). So if the roots are not 'sucking up' water to a sufficient degree there could be a lack of Ca moving into the root and through the xylem into the leafs. And if the rate of transpiration is not high enough the Ca will move more slowly to sink tissue (leafs). Not only that, but Ca is slowly moved into roots even at sufficient rate of transpiration, Ca is known to be "slow", while other ions are not (R. J. Dunham and P. H. Nye, 1976). Ca is poorly mobile inside plant tissue so older leafs can't give younger leaf their Ca very well at all (unlike what happens with nitrogen). All of those facts contribute to Ca movement into leaf, and thus contribute to Ca deficiency in leaf.
Even in plants with strong rates of transpiration, Ca deficiencies can and do occur. Your phrasing might be throwing me off. Earlier this post you said "Ca at CEC sites should easily separate from the CEC sites (and become plant available) via. acidic ions exudates by roots, other cations and pH of rhizosphere and soil solution." It now sounds not so easy!
In terms of uptake of magnesium it has been found Ca hinders uptake of Mg when Ca is in high concentration esp. vs. concentration of Mg. The higher the Ca vs. Mg the greater the Ca hinders uptake of Mg. The level of Ca to Mg (when Ca is in high concentration) that have been shown to hinder Mg uptake are 1:10 (Ca:Mg) to 1:20 an greater (B. Jacoby,1961; David P. Moore, Roy Overstreet, and Louis Jascobsom, 1961).
Rate of transpiration controls intake of water by roots (and thus Ca), movement of water - xylem (and thus Ca) into leaf. The lower the rate of transpiration the lower the uptake water and thus uptake of Ca and movement into leaf. Environmental conditions that affect rate of transpiration are mostly those that affect stomatal conductance (openness of stoma). Some examples are low RH, medium RH and high temp, high RH and low temp, high irradiance, low soil-water status (how dry the media is), light spectrum (blue light opens stoma, but red light closes stoma and green light would close stoma but in the presence-and-after blue light) and air movement.
The environmental condition with the biggest affect upon stomtal conductance is RH and canopy temp, along with low soil-water status (dry media) and high irradiance (lots of light).
What I am trying to write is: (1) I don't think CEC is the culprit in terms of Ca deficiency in young plant in fresh coco because the same deficiency isn't seen in s.peat. Considering that s.peat has higher CEC and normally higher bulk density; and (2) I think the reason for Ca deficiency in mostly young plants in fresh coco is in large parte due to rate of transpiration;
I totally disagree with this. Rates of transpiration are high in coco, under most conditions. Root systems become incredibly strong and effective. Of course, bad environmental conditions can affect transpiration and many other growth factors, in any medium. But as an explanation for Ca deficiency, this is possibly just clouding the issue.
and (3) the rate of transpiration is affected by a few environmental factors that reduce stomatal conductance; thus (4) depending upon the growers' specific environment she/he might or might not observe Ca deficiency when using the same coco, containers, ferts, water and clone as someone who did observe Ca deficiency in an different environment (ex. less-bright light and lower RH, or poor watering skills); finally, (5) if a grower does not flush fresh coco before use, and said coco was not well flushed by the manufacture, the coco would in essence be pre-charged with K and Na (at least), both of which will take up CEC sites, thus increasing percent base saturation translating into less potential CEC sites for Ca or Mg, meaning greater levels of Ca and Mg in soil solution and rhizosphere that can lead to increased Ca and Mg uptake; thus that could another factor why some coco growers experience Ca deficiency and some do not.
So you're saying that, in less-flushed coco, fewer Ca/Mg cations would be exchanged with the solution, leaving them free to be taken up by the plant? Less flushed coco leads to fewer deficiencies? I musta missed something.
YMMV, this is only my opinion
It's really interesting. Thanks for the posts! Peace.
References:
[1] "Symptoms of Deficiency In Essential Minerals"
Wade Berry, UCLA
A Companion to Plant Physiology, Fourth Edition by Lincoln Taiz and Eduardo Zeiger
http://4e.plantphys.net/article.php?ch=3&id=289
[2] "Marijuana Garden Saver: AKA The Complete guide to Sick Plants,pH, and Pest troubles!"
https://www.icmag.com/ic/showthread.php?t=11688
"Uptake of magnesium & its interaction with calcium in excised barley roots 1,2"
David P. Moore,3 Roy Overstreet, and Louis Jacobson
Plant Physiol. 1961 May; 36(3): 290–295
"Calcium-magnesium ratios in the root medium as related to magnesium uptake by citrus seedlings"
B. Jacoby
Plant and Soil
Volume 15, Number 1, 74-80
"The Influence of Soil Water Content on the Uptake of Ions by Roots. III. Phosphate, Potassium, Calcium and Magnesium Uptake and Concentration Gradients in Soil"
R. J. Dunham and P. H. Nye
Journal of Applied Ecology
Vol. 13, No. 3 (Dec., 1976), pp. 967-984
"Understanding Plant Nutrition: An Introduction"
Bill Argo and Paul Fisher, January 2008)
http://www.greenhousegrower.com/magazine/?storyid=109
Soil solution is the thin layer of water surrounding media particles, it's not the nutrient solution if you mean fertigation water, like the fertilizer+water in a bucket waiting to be applied to media.
CEC sites do not need Ca in equilibrium to Ca in soil solution, but cations (incl. Ca) in soil solution are often in equilibrium to cation held by CEC sites. This is due to CEC sites exchanging cations on a constant basis, it's not static. When roots and microbes release/create H+ ions those ions dissociate cations from CEC sites, as well as other cations that will dissociate Ca from CEC sites, and pH of soil solution and rhizosphere (separately from H+ ions).
The CEC sites of media will steal some Ca from the soil solution at first, but the soil solution and rhizosphere will steal Ca back from CEC sites, esp in media like coco with low bulk destiny. Because coco has low bulk density the Ca will not be 'held' strongly to the CEC sites, so they are more easily dissociated. That is why the CEC of coco and peat has marginal impact upon nutrient buffering and Ca availability to roots, and is why I believe the CEC isn't a concern or the cause of Ca issues for plants in coco.
What I wrote isn't contrary to what I wrote earlier, it's just expanding upon it. The effective CEC in coco is low, and even with the effective CEC the bond is not strong like it would be if coco had much higher bulk density (and clay particles) on par with soil.
When plants are young they have small roots system, thus they have less access to water, esp. low tension water after a time (as media dries water tension increases). What I mean is that a higher Perched Water Table is good for young roots that are have not yet extended deep into media. This means young roots have more access to low tension water, which helps the plant by allowing it to 'use' the water more easily, thus taking in Ca cations more readily.
A higher Perched Water Table isn't what we want when roots are bigger (i.e. deeper in media), but a higher Perched Water Table when roots are young (i.e. not as deep in media) won't stop roots from getting bigger.
The shorter the container the higher the PWT, and from my testing s.peat has a higher PWT than coco in the same height container and same packing by yours truly (i.e. compression of media).
Cannabis roots grow into the PWT all the time, ex., any time the roots reach the bottom of the container they are below the PWT, regardless of the height of the container. For coco and peat, there will always be a PWT, and below the PWT immediately after watering the media is generally anaerobic (i.e. < 10-13% air porosity). This does not stop roots from growing below the PWT, nor growing robustly below the PWT (i.e. root circling at bottom of container). Cannabis roots can handle being in PWT fine because when they are growing well (i.e. high rate of transpiration) they can suck up the water pretty fast, as well as evapotranspiration affects on reducing PWT over time.
Drip water system doesn't mean the soil-water status is high, or that the water tension is low, it depends upon how often the water is applied and at what rate it is applied. Using a top-down drench watering method (i.e. with a watering can) should provide higher soil-water status and lower water tension throughout all the media than drip emitters most of the time because drip emitters tend to hold media in a range of water content, often on the lower end.
To sum up: higher PWT when roots are small = good. Higher PWT when roots are large = not so good. Higher PWT when roots are small = greater access to low tension water thus greater (more efficient) intake of water, Ca and B.
The key is not every coco grower sees the Ca deficiency, I never have and I know others who never have either. Also, I do not think Ca deficiency some people see in young plants in coco is due to one reason like rate of transpiration, I think it's due to at lest three reasons: rate of transpiration, soil-water status and water tension.
Also a key to my belief that CEC is not the cause of Ca deficiency in coco is that people who grow with s.peat do not experience the same Ca deficiency, even though s.peat should show greater Ca deficiency than coco (if CEC is the cause of Ca deficiency in coco).
Those two arguments I believe make a very solid case that CEC isn't the cause (or not the main cause) of Ca deficiency some people find in young plants in coco. And that the rate of transpiration, soil-water status and water tension are the main culprits for Ca deficiency in coco when it's not seen in s.peat (considering peat has higher CEC and bulk density and not every coco grower sees Ca deficiency).
Considering those key points above, I think the cause of Ca deficiency has to be something variable (between coco growers) that is causing the Ca deficiency. CEC isn't very variable between coco growers, but rate of transpiration (e.g. stomatal conductance), soil-water status and water tension is...
It is easy for Ca cations to be freed from media like coco, easier then in soil. But even in soil it's pretty easy to dissociate Ca from CEC, e.g. with H+ ions that are ubiquitous in the soil solution and rhizosphere.
Rate of transpiration is not dependent upon the media, unless the media soil-water status is low (i.e. dry). Plants grown in coco do not have high rate of transpiration as a rule, nor do plants grown in s.peat. Rate of transpiration is dependent mostly upon stomatal conductance. And stomatal conductance is dependent upon the environmentals condition of the grow, separate from the media (except in the case of low soil-water status). So, plants grown in coco with good soil-water status can very easily have low rate of transpiration if the environment is reducing stomatal conductance, see the examples I gave in my last post. Simultaneously low RH (ex. < 50%) and high temp (e.g. > 75'F) has the biggest impact upon stomatal conductance and hence upon rate of transpiration.
Rate of transpiration is not clouding the issue, it is the issue. Ca uptake is most dependent upon rate of transpiration, which in turn is dependent upon stomatal conductance. The media has little effect upon both unless it's allowed to reach low soil-water status, esp. in drought like conditions (very low soil-water status -- that strongly impacts the direct control of stomatal conductance from RH, air temp and leaf temp; known as "air to leaf Vapor Pressure Deficit").
It takes roots a little while to get deep into media, thus when media has higher PWT and lower water tension (at high points in media) younger (and smaller) roots can more easily take in and move Ca to leafs (sink tissue).
Pretty much, if the coco is not well flushed it would (probably) hold more cations that can/will take up CEC sites, leaving less CEC sites for Ca and Mg. And because not all CEC sites are filled at any one time, the effect is exaggerated even more.
Percent base saturation is kind of a breakdown of the % of CEC sites filled by Ca, Mg, K and S. The ratios of those cations filling CEC sites is not set in stone, different media (and different bulk densities) will have different percent base saturation make-up. Also, beside the cations used to find percent base saturation, other cations can fill CEC sties too.
After thinking about the reason a coco grower who sees Ca deficiency can apparently 'fix' the Ca deficiency by adding extra Ca ("charging", assuming CEC is not the cause of the deficiency), it seems to me the greater concentration of Ca cations might off-set the reduced Ca uptake if caused by lower rate of transpiration (and possibility by lower soil-water status and higher water tension).
What I mean is if more Ca cations are available to the roots, they could take up more Ca even though the plant might have lower rate of transpiration, aside from CEC taking Ca cations.
In other words, say 100% of CEC sites are filled with Ca cations, and there is sufficient level of Ca cations in rhizosphere and soil-solution, the plant could still show Ca deficiency if the rate of transpiration is low, possibly exacerbated when soil-water status is low and water tension is high. However, if in the same situation Ca cations are in excess in rhizosphere and soil solution, that possibly could off-set (in part) the reduced Ca uptake due to lower rate of transpiration thanks to saturation of rhizosphere with Ca cations.
What I mean is if more Ca cations are available to the roots, they could take up more Ca even though the plant might have lower rate of transpiration, aside from CEC taking Ca cations.
In other words, say 100% of CEC sites are filled with Ca cations, and there is sufficient level of Ca cations in rhizosphere and soil-solution, the plant could still show Ca deficiency if the rate of transpiration is low, possibly exacerbated when soil-water status is low and water tension is high. However, if in the same situation Ca cations are in excess in rhizosphere and soil solution, that possibly could off-set (in part) the reduced Ca uptake due to lower rate of transpiration thanks to saturation of rhizosphere with Ca cations.
I wanted to note, this is only my position/belief, I could be wrong and I'm open to that possibility. However, so far all the info I have seen and what I have experienced tells me I am probably not wrong, and that CEC of coco is not the main reason some growers see Ca deficiency in younger plants...YMMV.
Maybe shooting Bill Agro an email with excerpts from my posts would be a good idea to get his 'take' on this topic...
Maybe shooting Bill Agro an email with excerpts from my posts would be a good idea to get his 'take' on this topic...
D
dramamine
Some interesting theories...
Your theory about higher Perched Water Table benefitting young plants does contradict usual thinking about more active root growth occuring as plants send out roots seeking water. Making water constantly available would inhibit this root activity, right?
And soil solution is, then, what we call fertigation water after it is applied? Or is there some sort of barrier that distinguishes it from the "thin layer" surrounding the media?
I think that excess calcium in the solution , rather than facilitating ample uptake as you say, would instead cause Mg lockout, among other possible scenarios.
And statements like this, I just don't get:
Your theory about higher Perched Water Table benefitting young plants does contradict usual thinking about more active root growth occuring as plants send out roots seeking water. Making water constantly available would inhibit this root activity, right?
And soil solution is, then, what we call fertigation water after it is applied? Or is there some sort of barrier that distinguishes it from the "thin layer" surrounding the media?
I think that excess calcium in the solution , rather than facilitating ample uptake as you say, would instead cause Mg lockout, among other possible scenarios.
And statements like this, I just don't get:
If PWT was "constantly available", in terms of no reduction of PWT, then yes it would inhibit root growth; but that's not what happens in media. We want low tension water to be constantly available to roots (ex. ideally moisture content always > 45% and < 65%), but that's not the same thing as a constantly available PWT that does not ebb and flow.
When the PWT is reduced over time, as happens in media, then the roots will not be hindered to a large degree (or even to a noticeable degree). The benefit from higher PWT for shallow/young roots should be greater than the possibly negative impact of PWT upon root growth. FWIW, the level of P in media has a bigger affect upon root growth than does PWT as far as I know (ex. more P anions = less root growth).
We can see examples of high PWT not negativity affecting root growth of cannabis all the time. Any time a grower uses a short container they are increasing the PWT (relative to total media height). So, a person who starts seeds in a jiffy pot, or a plastic beer cup will be providing a higher PWT than someone who starts seeds in a taller container. However, root growth of seedlings in short pots is as strong as root growth of seedlings in taller pots.
If the rate of transpiration is low, then the PWT will have a more deleterious effect upon root growth and root respiration because the PWT will not be reduced as fast/well (via. roots sucking up the water). If rate of transpiration is high (or at least sufficient) then the roots can pretty well 'suck up' the water below the PWT allowing increased air to reach lower into media as the PWT is reduced. Each time the pot is watered the PWT will again rise back up to it's pre-determined position (that is affected by height of media).
Yea, that is one way to word it, however, one doesn't need to apply fertilizer with water to affect soil solution. Just watering with plain water will affect soil solution. The soil solution is present regardless of fertigation. It's the soil solution that increases and decreases in water tension as media dries out and become more wet (respectively).
Y
YosemiteSam
Gotta say, based on personal observation, that I agree with spurr about the Ca deficiency being related to transpiration. I have a couple of grows and one has nice humidity and temp in veg...never a Ca deficiency. The other I fight to keep humidity up and if I am not careful transpiration slows and eventually leads to the Ca deficiency.
It can absolutely be fixed by getting temp/humidity in line without changing the nute mix one bit.
It can absolutely be fixed by getting temp/humidity in line without changing the nute mix one bit.
@ dramamine
I wanted to clarify something, if coco isn't well flushed and still has excessive Na (sodium) than that can make Ca and Mg un-available to the plant by 'locking' it to media colloids. If the Na level is high enough, media colloids can 'steal' Ca right out of root tissue!
So if someone uses un-flushed coco with high Na levels and sees Ca or Mg deficiency it could very likely be due to Na.
I wanted to clarify something, if coco isn't well flushed and still has excessive Na (sodium) than that can make Ca and Mg un-available to the plant by 'locking' it to media colloids. If the Na level is high enough, media colloids can 'steal' Ca right out of root tissue!
So if someone uses un-flushed coco with high Na levels and sees Ca or Mg deficiency it could very likely be due to Na.
D
dramamine
Right. The flush is very important, for sure. Also, I found the information regarding calcium uptake and it's connection to humidity/transpiration very useful. They are more closely linked than I thought, definitely. Some of your wording threw me off, initially, but I do appreciate the conversation.
G
grasspass
Thanks for the info guys. Where do you get citric acid for plants, for ph down. Should I dissolve some of my left over vitamin C pills?
D
dramamine
Citric acid should be at your health food store. It may be labeled as ascorbic acid. Vitamin pills would be fine, although I don't know what other fillers they may contain.
vaped
Active member
right now I blast out the ionic for soil andd coco. every time i get 3 weeks into flower and switch to bloow nutes boom shit yellows but the buds just keep growing. I used H&G wich is a 2 part and stuff stayed green the whole route. I think the Ionic for soil and coco might do a better job. Things yellow out but the leaves dont get chlorotic and the buds swell. In veg i run Ionic grow, greenfuse root, greenfuse growth, calmag, liquid Karma and drip clean. After three weeks of bloom I run Ionic bloom,Ionic boost, greenfuse bloom stim, liquid Karma, calmag, and drip clean. this mix will get you elbos of nice buds. let the coco dry a lil between watering then drench to run off. my scales are praying for a brake.
