Plants self-regulate uptake of ions; they control it, not us, unless we overdo ferts

spurr said:

I am looking forward to what you find. You seem to have a very good grasp of this matter, and you and I agree 100%: let the plant take what is wants, don't overfeed

I wrote a long and very well referenced thread elsewhere a while ago about cannabis tissue assays for nutrients and why less P is needed than is most often used, etc. I could post up some info in a different thread someday if your interested.

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I'm not actually sure what you guys are talking about all plants can only take what they can take no more no less. Most ppl over do it with fertilizers and the plant will simply disguard the excess so it's a total waste indoors. peace out Headband707

Im a firm believer in less is more. I always start at quarter the recommended dose ferts and finish at a lil over half the bottle recommended dose. I think alot of people feeding at full strength are throwin money away.

Dopeboy668 said:

Im a firm believer in less is more. I always start at quarter the recommended dose ferts and finish at a lil over half the bottle recommended dose. I think alot of people feeding at full strength are throwin money away.

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Truer words were never spoken lol.. All manufacters will try to sell you ferts at optimal conditions but for most if not all indoor conditions, indoors don't have these conditions and plants don't need and will not take this much fert.A plant can only take what it needs no more no less the rest will just end up in your soil to be flushed away with the next watering. A real waste of cash..You will know if you have given your plant too many ferts if the tips are black.Less is more and look into things like seaweed , and various trace elements because ferts aren't the only game in town lol peace out Headband707

look at the plethora of aminos on advanced nutrients booster products and sweet products and youll start to see why they are so "advanced"


quarter strength was what I was taught when reagan was in office

Of course they do and always have. Organic takes it much farther.... There is a reason you can have rich organic amended soil with PLENTY of N left in it at the end of flower, yet the plant won't take any of it up because it knows when it's lifespan is over. It's an annual.

Another reason bottled fertilizers give such high doses is to A: get you to buy more.. B: are used on outdoor plants which can take WAY more fertilizer because they get pure sunlight.

Pretty sure that is why people cut the doses down so much, the less light available, the less food is needed by the plant. (in basic terms)

staff11 said:

Of course they do and always have. Organic takes it much farther.... There is a reason you can have rich organic amended soil with PLENTY of N left in it at the end of flower, yet the plant won't take any of it up because it knows when it's lifespan is over. It's an annual.

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AGREED!!!!! lol .. she just lets it sit there and it just flushes away with my greed LOL LOL

headband 707 said:

all plants can only take what they can take no more no less. Most ppl over do it with fertilizers and the plant will simply disguard the excess so it's a total waste indoors. peace out Headband707

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Does this mean nutrient toxicity is a myth?

Greyskull said:

found it!!!!



from Canna's webpage: http://www.cannagardening.com/node/1568?page=0,5

Because CANNA Coco is 100% organic it has a relatively high Cation-Exchange Capacity (CEC). This means the substrate has the ability to hold and retain certain nutrients vigorously thus requiring these nutrients to be supplied in a special form that remains available to the plant.

Due to the special Coco characteristics in combination with the unique pre-buffering process, it is possible to combine vegetative and flowering nutrients in one nutrient mix. The medium and the plant itself control which nutrients are released to the plant at just the right times.

This means the grower doesn’t have to worry about the proper point to convert from grow to bloom nutrients!

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its an "info paper" on their coco product line. unfortunately it doesnt go into detail as to HOW/WHY it works... only that thats whats going on.

discuss....

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Hey,

CEC has nothing to due with plant ability to self-regulate uptake of ions. CEC is really only a concern in media with high bulk density, and in media like coco or peat CEC is a non-issue. This relates to the quote/paper Carl posted above. If one was to increase the bulk density of coco or s.peat (via. heavy compaction or adding dense organic matter like compost) then the CEC would not be a non-issue.

The cations held in CEC sites can be freed via. acidic exudates from roots (ex. acidic H+ protons) and microbes, it can also be freed from interaction with other cations, and pH of soil solution.

The soil solution generally hold cations in equilibrium to cations held in CEC sites (usually once most CEC sites are filled).

Lots of people and companies that sell coco make claims about how great the CEC is, and how CEC of coco affects Ca availability to roots, neither of those claims are true to the degree the claims makers attest (again, see the paper Carl provided). S.peat has greater CEC than coco and peat doesn't have issues with Ca availability to roots...

If there really is an issue with Ca availability to roots in coco (which I have never noticed) than the issue is not due to CEC, it could be due to poorly flushed coco holding higher levels of P, K and S ions, which could affect availability of Ca ions. I for one do not believe there is a Ca 'issue' with coco.

The whole topic of CEC and AEC is misunderstood by companies selling products (like coco) that are thought of to have high CEC. For example, CEC of most humus/clay rich soil is around 5-20+ meq/100g, and coco as CEC around 40-60+ meq/100g and s.peat has CEC around 60-80+ meq/100g. Of all those media, it's only the soil that a grower needs to be concerned about in terms of CEC. Or coco or s.peat with intentionally increased bulk density.

The CEC fo coco is not only lower than s.peat, but the bulk density of coco is less than s.peat too! Thus, the CEC of coco is a non-issue, and any company who claims otherwise needs to study up...

Canna is full hot air on this issue of CEC and coco...

Zen Master said:

can you put this in doodoo dumb language?

what I'm getting is

"no matter what you feed it, the plant is only gonna take what it wants, not what you force down its gullet"

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Yup, except for ammoniacal N, and unless the osmotic factor is so high (ex. very high EC) that it overrides plant self-regulation of ions like nitrates, P, Ca, Mg, etc.

Basically we should try to provide sufficient level of ions, and let the plant take what it needs depending upon it's growth stage. Let the plant be the 'boss'.

Another point on this topic is the false idea that we need 'veg' and 'bloom' ferts. All we need is one fert and use it all the time, this is how the Lucas formula is used. When I used to use the Lucas formula that is how I used it too, for many years. The plant will take what it needs when it needs it; if it takes in more than it needs it will store it in tissue for later use (esp. in terms of partially-mobile and fully mobile elements within plant tissue). Also false is the idea that we need to, and should, boost P during pre-flowing and flowing.

The topic of why plants need much less P than most cannabis growers think is not really relevant to this thread, but suffice it to say over 50 ppm of soluble (i.e. plant bio-available) phosphate anions is unneeded and can hinder stalky plant growth. To keep phosphate anion soluble it's wise to include citric acid in your fertigation water. Ex. Fe cations will make phosphate anions insoluble; but if citric acid chelates the anions first the Fe won't make them insoluble--thus the anions won't precipitate out of solution and no longer be plant available. The greater the P (and N) the greater the plant will stretch and the greater the internodal length, esp. important for pre-flowing when people tend to boost P with bloom boosters. During pre-flowing is a time when it's best to NOT boost P, but boosting K is fine because it has little effect upon internodal length/stretch and can increase yields. IMO the efficacy of bloom boosters comes from the K, not the P.

Here is what I feed when using chems, I use this all the time for vet to harvest. There is no need to use grow and bloom ferts, as has been shown for a long time by those using the Lucas formula:

Spurr wrote:

Below is my best effort to make an ideal chem fert mix using General Hydroponics Flora series to provide cannabis with sufficient level of elements. Ideally I would drop N to around 100 ppm so using maybe 3-4 ml of GH Micro and using 2.5 ml of CalMag+ might be better but I haven't done the math for that yet. The following mix is what I have been recently testing with ACT to see how it effects the microbes; no data to report as I haven't done enough testing yet. I have tested the following mix for growing cannabis without organics and it preformed better than the Lucas formula without excess ions found in the Lucas formula (which is based upon flawed claims by Ed Rosenthall, Mel Frank, George Cervantes, et al.):

My test mix with GH Grow/Micro/Bloom at 5/5/5 ml with CalMag+ at 5 ml and ProTeKt at 2.5 ml (all per gallon; along with citric acid to keep P anions soluble):

• Total N...140 ppm
• Nitrate N...130 ppm
• Ammonicial N...10 ppm
• P.....39 ppm
• K.....155 ppm
• Ca...126 ppm
• Mg...46 ppm
• S.....15 ppm
• Fe....3.1 ppm
• Mn...0.8 ppm
• Si.....56 ppm
• total PPM = 580
• Ca:Mg ratio = 2.7
• Nitrate N:Ammonicial N ratio = 13

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FWIW, here is data from CNS17 (from bontaicre) thanks to Carl Carlson:

Carl wrote:

15 ml per gallon

• Total N - 137 ppm
• Nitrate N - 131 ppm
• Ammoniacal N - 6 ppm
• P - 40 ppm
• K - 152 ppm
• Ca - 128 ppm
• Mg - 23 ppm
• S - 50 ppm
• Mn - .22 ppm
• Mo - .02 ppm

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ganjaments wrote:

Headband707 wrote:

all plants can only take what they can take no more no less. Most ppl over do it with fertilizers and the plant will simply disguard the excess so it's a total waste indoors. peace out Headband707

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Does this mean nutrient toxicity is a myth?

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No, plants can't self-regulate uptake of ammoniacal N (like ammonia and ammonium) and it becomes phytotoxic to roots (burns them) when the plant is not able to move enough sugar (from photosynthesis) into the roots to convert the ammoniacal N into plant usable forms. When there is a lack of sugar, or the uptake of ammoniacal N outpaces movement of sugar into roots, phytotoxicity sets in.

Ammoniacal N is what causes nutrient toxicity from N, not nitrates AFAIK. In terms of P, the plant can self-regulate uptake of phosphate anions and excess gets converted (at least most of it) and stored in plant tissue.

Plants can self-regulate uptake of (at least) nitrates, P, Ca, Mg, and probably K, but not ammoniacal N (e.g. ammonia and ammonium).

The plant will take what it needs when it needs it; if it takes in more than it needs it will store it in tissue for later use (esp. in terms of partially-mobile and fully mobile elements within plant tissue). Plant self-regulation of ion uptake doesn't mean the plant stops taking in 100% of said ions, but it can/does reduce uptake to small or great degrees.

FWIW, if ammonium and nitrate is co-applied the plant will take up the ammonium faster and use it faster. For the first few hours (ex. in a fresh hydro rez) the ammonium will increase uptake of nitrates, but then after a few hours ammonium will decrease uptake of nitrates by the plant. I assume this is because the ammonium is converted into amino acids and moved into the phloem, that in turn signals the plant to reduce uptake of N (as nitrates).

I wanted to expand on the issue of CEC and bulk destiny for a minute because it's an important topic and many claims about efficacy of CEC in peat and coco are false. The reason is that facts about CEC functions in soil does not translate into CEC functions of peat and coco due to their low bulk density.

I agree that CEC is an important consideration in terms of cation exchange/reservoir and pH buffering, if the bulk destiny of media is above ~ 0.25 g/cm^3 to above 0.5 g/cm^3. However, if people use only coco (~ 0.10 g/cm^3) or only peat (~ 0.15 g/cm^3) than the bulk density will be low and thus the CEC won't 'do it's job'. Mixing in perlite and vermiculite doesn't increase bulk density to any worthwhile degree.

For reference, bulk density of good, humus-rich and biologically active soil (e.g. "chernozem") is ~0.5-1.25 g/cm^3; and average bulk destiny for regular soil is 1 g/cm^3 to 2 g/cm^2. Once bulk density exceeds 1.6 g/cm^3 roots can not penetrate soil well.

Considering most people here (in the synthetic fert forum) do not add organic matter (OM) with high bulk destiny to peat or coco they have low "effective CEC" (i.e. the CEC that is useful). To increase bulk density (and thus effective CEC) of peat or coco we can add OM with high bulk density or we can intentionally compress the media (but compressing isn't a good idea). For those who do not want to add OM to coco or peat addition of sand will increase the bulk destiny, but using sand is less than ideal.

Adding humus rich compost is good because it is high in CEC (from the humus and clay often found in compost) so compost helps in two ways: (1) it increases CEC and (2) it increases bulk density. Along with compost and vermicompost I add micronized aluminosilicate zeolite powder ("zar-min") to my media to also increase CEC because zeolite has some of the highest CEC one can provide; the other being humus. Adding said zeoltie is also good because it is "paramagnetic" rock powder, and increasing paramagnetism of media is a great thing to do (but out of scope of this thread).

Using good humus rich vermicompost is a good option in place of compost to increase bulk density and CEC at the same time.

Both vermicompost and compost provide lots of other benefits to media and plants besides bulk density and CEC. Of the two, fresh and humus rich vermicompost is probably the better choice (adding compost or vermicompost from 10-20% by volume is a good goal, I use 10% vol/vol)

For quick reference:

Coir Dust, A Viable Alternative to Peat Moss

http://flrec.ifas.ufl.edu/Hort/Environmental/Media_Nutrition/COIR potential.htm

http://www.informaworld.com/smpp/945159584-24047777/content~db=all~content=a905417032~frm=abslink

Properties of coir dust, and its use in the formulation of soilless potting media

Author: Kevin A. Handrecka

Abstract
Data from two experiments have shown that for adequate growth of Petunia 'Celebrity Salmon' in soilless potting media based on or containing coir dust it was necessary to amend the media with Ca, S, Cu and Fe. When coir dust is used as a direct replacement for natural peat, about 10 mg/L medium extra N per week must be provided. The high K content of coir dust means that fertilizers need not contain as much K as is normally used for plants in media based on other products. The high Cl content of some coir products requires that they be leached if they are to make up a high proportion of a medium.

The low CEC of the coir products (21-30 m.m (+)/L, compared with 78 m.m (+)/L for a peat), indicates a low ability to retain cations and to buffer against pH change. Two coir products had lower air-filled porosities than did the peat tested and they retained more water at 10 kPa suction.

hey bro,

Coir Dust, A Viable Alternative to Peat Moss

http://flrec.ifas.ufl.edu/Hort/Envir...0potential.htm

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yea that is a good read, I think it helped to start interest in coir in commercial horticulture years ago, and the references cited are good too. Coir dust = coir pith, the same stuff we know as coco coir.

OsWiZzLe said:

http://www.informaworld.com/smpp/945159584-24047777/content~db=all~content=a905417032~frm=abslink

Properties of coir dust, and its use in the formulation of soilless potting media

Author: Kevin A. Handrecka

Abstract
Data from two experiments have shown that for adequate growth of Petunia 'Celebrity Salmon' in soilless potting media based on or containing coir dust it was necessary to amend the media with Ca, S, Cu and Fe. When coir dust is used as a direct replacement for natural peat, about 10 mg/L medium extra N per week must be provided. The high K content of coir dust means that fertilizers need not contain as much K as is normally used for plants in media based on other products. The high Cl content of some coir products requires that they be leached if they are to make up a high proportion of a medium.

The low CEC of the coir products (21-30 m.m (+)/L, compared with 78 m.m (+)/L for a peat), indicates a low ability to retain cations and to buffer against pH change. Two coir products had lower air-filled porosities than did the peat tested and they retained more water at 10 kPa suction.

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That too is a good paper, but AFAIK, they tested coir pith without flushing it first, and coco coir we buy today is generally flushed by the manufacture, e.x. bontinacre cocogrow.

The info about the CEC is sound also, in that coco has reduced CEC vs. peat; besides the topic of both having low bulk density.

spurr...your formula appears to have a lot of calcium and not a whole lot of S, at least to me. Could you comment on these levels and why you think they are appropriate?

Would you also comment on what EC you run in veg and flower? How much citric acid do you use and where do you source it?

Would you also comment on your use of PGRs?

sure, but not today, sorry.

Subscribed. Dense thread. Thanks to everyone for the work.