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Lack of Potassium?

On my amazon swords i used to get yellow leaves, that would eventually die off,
then i started dosing tropica plant nutrion plus.
Hi Tom,
I agree with George. It's much too simplistic to assume that a K deficiency can be detected by any one symptom, even those listed in the various deficiency charts. Unlike Carbon and the other macronutrients, K is not integrated into plants' cellular structure which would cause an obvious structural failure. There are few, if any direct K related algal dependencies. The role of K is to act as a catalyst in various reactions. K is very mobile but mostly resides as the cation K+ in the cytasol, which is liquid enclosed by the cell membrane. K+ does not bind itself to organic molecules such as sugars but instead is more of an electrolyte similar to the liquid in a car battery, generating voltages across the cell membrane and thus attracting or repelling other ions into and out of the cell.

The efficiency with which plants execute their various functions is related to K+ levels. For example, K plays a role in the transfer of nitrate from the roots to the shoots and leaves. Without adequate K, nitrate accumulates in the roots and a feedback mechanism to the root cells stops further nitrate uptake. This is especially relevant to hobbyists who use predominantly root based dosing such as in the ADA scheme. So one may observe the yellowing associated with N deficiency in such a case.

Energy conversion, carbohydrate formation/translocation, N metabolism and other metabolic processes in plants are controlled by enzyme systems, at least 50 of which are activated by K. K activates the movement of water and solutes, it regulates the stomata opening and thus, intake of carbon dioxide, the plants' carbon source and it affects the pH of plant cells by neutralizing the excess of negative charges on proteins and nucleic acids.

So as a result of the indirect effects, it's very difficult to tell whether one has a K deficiency or whether a a direct deficiency of the other macronutrients is present. This is the primary reason for the "add a bit more of everything" EI philosophy which tends to drive the lean dosers mad. :rolleyes:

Cheers Clive,

So is it fair to say that a lack of K would ultimately slow down the growth of the plant?

And if you add too much K, it wouldn't particularly benefit algae?

Also, if there is too much K, would the plants then show deficiencies of the other nutrients, or would they only take in the K they need?

Hi Tom,
Yes, chronic lack of K ultimately slows growth due to the wide range of activities and processes in which it is involved in, - not the least of which is Photosynthesis and Amino acid/Protein synthesis. In fact, farmers and gardeners often dose extra K which promotes the nutritional value of their crop yields. In fact any crop that is a sugar based product needs lots of K to synthesize and even to store the carbohydrates. Crops such as Sugar cane, sugar beets, sweet potato and so forth are optimized with lots of K. K is also essential for root development and function so that tubular crops are also optimized via massive K dosages. K is used in the formation, translocation and storage of the carbohydrates so that grain crops such as wheat, corn, and barley also have higher yields when fed high K dosages. K is also essential in the formation of oils so that oil crops such as soybean, peanuts and flax produce higher yields with more K. K is involved in so many processes that the optimization effects are wide ranging.

While algae are plants too, and while they do use K, their blooms are not induced by high available K concentrations.

Too much K never hurts and does not drive the downstream effects to cause shortages that the other macros do. In fact, the concentration of K within the plant is reported to be much higher than is actually necessary. This might be considered a form of long term storage (what Barr calls "Luxury uptake").

A brief history of K: Hundreds of years ago wood and other organic matter was burned in pots in the process of fabricating soap. This burnt residue, or, ash was called unsurprisingly, "Pot Ashes" and was basically a cocktail of various Potassium salts. After rinsing, the ashes were dried and later combined with animal fat to produce the soap. Pot ashes, later became known as Potash and is therefore associated with K - in effect Pot_ash_ium or Potassium. Now, any salt of K is referred to as a type of Potash, so for example the expression "Potash of Nitrate" is simply Potassium Nitrate (KNO3) and Potash of Sulfate is Potassium Sulfate (K2SO4).

Out of curiosity, how do you manage to avoid adding any Potassium at all?
Well, Phosphorous and Nitrogen are easily produced by fish waste and fish food (although if the fish food is vegetable matter then it probably contains some K) as well as other forms of organic waste so some hobbyist decide to not add any extra macronutrients and instead decide on supplementing micronutrients via popular brands such as Seachem's Flourish or Tropica's TPN for example. Probably 90% of the commercial fert mixes on the market are just micronutrients with no N, P, or K. That seems to be changing now as folks finally realize (and vendors finally admit) that NPK are about 1000X more important than trace elements.

I thought TPN contained potassium. It doesn't give a breakdown, to be sure. But since TPN+ includes NP, I would have figured regular TPN would be K plus micro-nutrients, just like JBL Ferropol. That way people with fish add regular TPN, and people with no, or little, fish stocks, add TPN+ instead. i.e. TPN = K and micronutrients, TPN+ = K & micronutrients + NP.

That was my assumption, anyway.
As far as I know both TPNs do have K in them. Its N and P that are missing from the 'non plus' version

Yes, I rechecked and that's true, although TPN has less than 1% K so if it's being dosed as a trace you're not adding very much K really. TPN+ has a little over 1% K and most dose this more heavily in high light tanks so more K gets pumped in.

Compare that to how much K one adds when dosing KNO3; 6.5 grams of KNO3 (about a teaspoon) adds around 4 grams of K, so that's almost 40% by weight.

According to Barr's analysis, the ADA solution for K is Brighty K which, if dosed per bottle adds 3.4 ppm per day (1 pump per 20L). Green Brighty Lights and Green Brighty Shade add very small amounts (around 0.15ppm) while the Brighty Steps 1 and 2 have negligible amounts.

Incredibly informational thread! Took a little while to wrap my head around the whole EI business, as I tend to want to understand every little bit of information, and stop worrying about absolute measurements. But threads like this feeds that little bit of my brain that screams for MORE DETAILS!
Ceg, you should have a prefix to all your posts saying "Don't panic" in large friendly letters :lol: You make it all so simple and obvious. After a year on UKAPS I feel like I'm almost ready to take a degree in Aquatic Macrophytes!