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Targeting Potassium
- Thread starter hypnogogia
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Oldguy
Member
Might be simplistic but how do you account for very good plant growth and high potassium levels.
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Ambiguity when a clear question is asked isn't very helpful. 😊
I have always assumed that different plants have different nutrient requirements, perhaps linked to their natural habitat. For example, a plant whose natural habitat has soil that is low in magnesium is probably going to be ok in an aquarium with high K+ levels that may inhibit Mg2+ intake since they need very little. This table suggests that magnesium levels vary a lot...
_Maq_
Member
I'm an amateur when studying plant physiology, that's true. But when I read about plants' internal mechanisms, I don't think that there's a plant which "needs very little Mg", par example. Let's think about it. Mg is a key element of chlorophyll. Chlorophyll and photosynthesis are always the same, with some minor variability. Therefore, the amount of photosynthesis - the only source of sugars, i.e. energy and most of plant's tissues - is linearly dependent on the amount of Mg a given plant assimilates. So, there can't be a plant that needs "less" magnesium.
However, there are plants which can be adapted to environment with Mg shortage. I think that such plants posses some methods how to cope with such an adversity. Perhaps more Mg transporters in root cells, something like that.
Similarly, when you read that some aquarium plants "require plenty of iron", the situation is the same. No plant "needs" more or less iron. The function of iron in plants is well known; it is a part of an enzyme which catalyzes formation of chlorophyll. What is the difference among plants, then? It is their adaptation to conditions when iron is scarce, or rather, when iron is hard-to-take-up, i.e. upon higher pH or increased content of bicarbonates. Some plants developed strategies how to get iron even in these adverse conditions, other plants did not, and the latter are limited to soft acidic waters. [Or, a huge excess of iron bound in advanced chelates.] About such plants we say "they are iron hungry", but in fact, they don't uptake any more (neither less) iron than the others.
I'm not sure and I'm trying to find out. Seriously. I do not just talk, I study science and perform experiments.
My theory, a merely unverified theory, is following:
(1) CO2 is a source of energy for plants. CO2 injection is a source of plentiful energy.
(2) To take up or exude any ion (nutrient), a plant needs energy.
(3) If nutrients are in poorly balanced ratios, energy requirements on plants are higher.
(4) However, with CO2 doping, plants can easily handle various adversities, incl. imbalance in nutrient availability. Par example, they can exude redundant potassium over and over. (Scientific literature calls this phenomenon "futile cycling".)
Oldguy
Member
A very good point. Hornwort for example requires silicon more than most.
I also wonder if commercially grown plants, taken as cuttings and root division, have over generations been selected as those plants that grow well in the nutrient conditions that the grower provides. Those that don't grow well fall by the wayside.
It could be pot luck to the best growing conditions required by the plants that we actually buy.
_Maq_
Member
Silicon does not belong among nutrients, i.e. elements without which plants cannot complete their life cycle. Silicon belongs among so called beneficial elements. It helps building supportive tissues and as such, it deters herbivores. Ferns and grasses are typical "silicon-hungry" plants, but still, they can live without any silicon.
Yes, Ceratophyllum ranks among aquatic silicon eaters. It seems that it provides with competitive advantage, protection of tissues against herbivores and fungi.
Of course, it worked like that for millenia. Yet not only that. The reverse is valid, too. Par example, selected cultivars of wheat cannot survive in natural conditions. Farmers preferred yield over competitive abilities. So, wheat cultivars must be "cultivated", otherwise they fail in competition of wild grasses.
Oldguy
Member
Never said it was. However in my experience hornwort just falls apart without an adequate supply of silicon and would have difficulty surviving.
If we are competing for 'hair splitting' then hornwort doen't eat. lol.
Hi,
Is it possible that plants just get used to high potassium environment if it gradually increases over time ?
I'd like to contribute to the potassium discussion, not from the scientific point of view, rather what I observed in my tank.
I started brand new set up using 100% RO , which I re-mineralize to 1KH with K2CO3 and boost GH with CaCl2.
In addition to that I use KNO3, MgSO4 and K2PO4 and trace mix bi-weekly and my aim was to keep the levels at around 30N 2P 30K 8Mg and 8Ca. Obviously potassium started to accumulate, which I could quickly resolve with back to back water changes, but I saw on UKAPS, that some users had K in their tanks at 100ppm with no issues.
I also could see no issues, so I ignored it - plants were growing really well. That is until I introduced mature plants that did not grow in my tank from the start. Those did not like the water at all, I would say they got shocked. At first, I thought that could have been the high light, but it's been weeks and I've see new growth not getting better.
For example Hygrophila Corymbosa below, or Bucephalandra Kedagang.
Another thing I noticed is Ludwigia Arcuata, which someone mentioned in this thread grew really well from the start until I recently hacked it quite low. It never came back like it was, just struggles in the back of my tank- getting some colour but clearly not how it used to be.
Buce is from my low tech setup that has some potassium in it, but nowhere near as my high tech tank. Hygrophila was purchased online, so I do not know what water it was in previously.
My readings are as follows.
K 100ppm+
N 20-30ppm
P 2-3ppm
Mg - 15ppm
Ca - I cannot really check, but I put around 10ppm minus what was used by plants
Fe - 2ppm
From this week I am going to stop K2CO3 and CaCl2 and swap KNO3 to Ca(NO3)2 and see if struggling plants get any better.
I will revert back to KNO3 once I bring potassium down to around 30ppm, so It will take few weeks.
I will then let you know what's happening.
Cheers,
Matt
for the record full tank pic:
Is it possible that plants just get used to high potassium environment if it gradually increases over time ?
I'd like to contribute to the potassium discussion, not from the scientific point of view, rather what I observed in my tank.
I started brand new set up using 100% RO , which I re-mineralize to 1KH with K2CO3 and boost GH with CaCl2.
In addition to that I use KNO3, MgSO4 and K2PO4 and trace mix bi-weekly and my aim was to keep the levels at around 30N 2P 30K 8Mg and 8Ca. Obviously potassium started to accumulate, which I could quickly resolve with back to back water changes, but I saw on UKAPS, that some users had K in their tanks at 100ppm with no issues.
I also could see no issues, so I ignored it - plants were growing really well. That is until I introduced mature plants that did not grow in my tank from the start. Those did not like the water at all, I would say they got shocked. At first, I thought that could have been the high light, but it's been weeks and I've see new growth not getting better.
For example Hygrophila Corymbosa below, or Bucephalandra Kedagang.
Another thing I noticed is Ludwigia Arcuata, which someone mentioned in this thread grew really well from the start until I recently hacked it quite low. It never came back like it was, just struggles in the back of my tank- getting some colour but clearly not how it used to be.
Buce is from my low tech setup that has some potassium in it, but nowhere near as my high tech tank. Hygrophila was purchased online, so I do not know what water it was in previously.
My readings are as follows.
K 100ppm+
N 20-30ppm
P 2-3ppm
Mg - 15ppm
Ca - I cannot really check, but I put around 10ppm minus what was used by plants
Fe - 2ppm
From this week I am going to stop K2CO3 and CaCl2 and swap KNO3 to Ca(NO3)2 and see if struggling plants get any better.
I will revert back to KNO3 once I bring potassium down to around 30ppm, so It will take few weeks.
I will then let you know what's happening.
Cheers,
Matt
for the record full tank pic:
_Maq_
Member
To this question I can say 'no'.
MichaelJ
Member
Right. Plenty of us around here are able to - or have been able to - grow plants successfully at high potassium levels, and high potassium levels relative to Mg levels, be it low-tech or high-tech. I've been running my low-tech tanks at exorbitant K levels in the past and my plants did just fine.
My take-away from @_Maq_'s experiment is that there appears to be a correlation between low K to Mg, that enables the plants to do better, thats all. How much of a role other nutrient amounts and water parameters plays in this experiment is unclear to me. My own lean tank is now low K to Mg (1:5:10), my other tank is relatively close to equal amounts of K and Mg (1:1:3), and it's been that for quite a while now.
Cheers,
Michael
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_Maq_
Member
I take arguments of yours and others seriously. It seems that further research and experiments on this issue are necessary.
Based on my Experience and Experiments, you can certainly grow plants under low or high K regardless of ratios, or any ratio in general. but, the problem is that some plant struggles while some doesn't care much, in most cases people has already tried everything they could think of, such as raising their CO2 to Extreme, Excessive Nutrient's and yet they still see Nutrient Deficiencies or low CO2 Deficiency. Once you start making changes to the Nutrients and Ratios, you can start to see the improvements.
I can grow varieties of difficult plants under same setups and cause them to stunt or un stunt and deficient or not deficient simply by changing the Ratios. if we could grow the plant even better under Different sets of ratios such as the one being discussed here regarding Ca;Mg;K ratio, I do not see any harm.
John q
Member
The thing that confuses me is that a lot of folks can grow, stunt, un stunt, or make plants look deficient by simply changing the levels of co2. And yet this gets dismissed as....
maybe, just maybe we should consider a C:N: P:K:Mg ratio.
( just throwing it out there guys)
MichaelJ
Member
Hi @John q ... I am not sure it gets dismissed... While I am not a CO2 user and probably never will be, I do believe - based on the thousands of posts I've read over the years - that if your using CO2, the CO2 application (CO2 dosing / proper flow / pH drop etc.) should be looked into first when dealing with poor plant health, algae etc. before fertilizers. When CO2 is up to par the next thing would be water parameters and the constituent of the fertilizers (including ratios eventually). The ones among us doing low-tech are lucky enough that we can cut right to the chase... 🙂
Cheers,
Michael
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Hi all,
A floating plant always had access to <"atmospheric CO2">, and that takes <"CO2 deficiency out of the equation">. Clive (@ceg4048 ) is convinced that most deficiency symptoms relate to <"lack of CO2">, I've never been in a position to answer this from experience (and he may well be right), because I've never used CO2. This meant that the only way of disentangling CO2 and nutrient effects (for me) was to make CO2 "unlimited" and take CO2 availability out of the equation all together.
The factors that initially led me to <"Duckweed (Lemna minor)"> were:
cheers Darrel
That was one of the main reasons for using a floating plant in the <"Duckweed Index">.
A floating plant always had access to <"atmospheric CO2">, and that takes <"CO2 deficiency out of the equation">. Clive (@ceg4048 ) is convinced that most deficiency symptoms relate to <"lack of CO2">, I've never been in a position to answer this from experience (and he may well be right), because I've never used CO2. This meant that the only way of disentangling CO2 and nutrient effects (for me) was to make CO2 "unlimited" and take CO2 availability out of the equation all together.
The factors that initially led me to <"Duckweed (Lemna minor)"> were:
- Access to 415 ppm CO2.
- Access to atmospheric oxygen
- First access to PAR
- Quick turn-over of leaves
- Morphological plasticity in leaf size, dependent on nutrient availability
- A <"differential greening response"> to <"changing nitrogen levels">.
- Floating leaves that can't become algae choked
- Roots in the water column, removing substrate nutrient dynamics from the equation.
- Easy to remove from the tank <"Removing Duckweed (Lemna minuta) - any natural solutions?">
cheers Darrel
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Anything special about frogbit/duckweed ?
I have a heavily planted shrimp grow out tank with no substrate and just RO water (with some GH booster only) which shows deficiencies in the submerged plants while the floaters are thriving. It almost makes me think floaters are feeding off dying submerged plants. Apologies for the quality of the pictures, I have no way to avoid the glare.
Okay, so I am going to challenge above based on what I observed - please read below.
I did change my EI fert regime as I said few posts above- I replaced KNO3 with Ca(NO3)2. I stopped CaCl, ceteris paribus.
Fast grower (Hygro polyspherma) reacted 1-2 days later, it stunted when I halved potassium to what I guess was 60+ ppm.
So the plant definitely needed that elevated level of potassium for something - it got used to having abundance of it and it was not happy when I took it away. All the new growth looked droopy - even new off shoots in the bottom of the plant looked sad. I still dosed K2P04, so they got a little bit potassium from that, clearly not enough. See the picture.
I trimmed it during the following water change, and it picked up the next day (K at around 30+ppm) - I'd say it is getting used to lower K levels and looks way "better" now. Again, see the picture below.
As for the other plants... Ludwigia arcuata reacted, it's not growing perfectly yet, but it is showing some more colour. Below before and after shots. It may not look radically different on the picture, but I can see it definitely responded positively to lowering the Potassium.
Hygro Corymbosa is still growing with its leaves curled, perhaps it needs more time. I bought the plant online, the stem is very thick, like a terrestrial plant twig. I ordered some submerged corymbosa from Tropica and will plant it right next to mine for reference. Buce shows no change either. No changes to any other plants.
Full tank shot for reference
I am going to continue to reduce potassium further, I purchased some other salts like potassium sulphate and urea, but I am not sure how to use the latter yet. Once I get familiar I will try to dose NPK all form their own sources, so I can avoid the build-up. I will update you on how I get on.
Best,
Matt
Hi all,
Cheers Darrel
No, not really. Any floater would do, it just needs to be fairly tolerant and, ideally, with a "leaf green" green leaf.
Possibly, but it is most likely to be CO2 or light. The other advantage, after access to CO2, of a floating plant is that it has first dibs on the light.
Cheers Darrel
_Maq_
Member
In some cases, plants posses two transporters for the same nutrient - low- and high- affinity ones. High affinity transporters are activated when the nutrient in question is in short supply. I'm not very sure how long it may take to activate these transporters. Transporters are specific proteins. It may take several days, I can't exclude that.
Still, I don't think this explanation is likely because you are still in the range of overabundant potassium.
I must admit that the more I study these questions the less I'm firm in any conclusions. I'll definitely do more tests related to cation ratios (i.e. K:Mg:Ca, possibly including Na).
