High Potassium is not necessary for flowering?

Alright, so what is the consensus on potassium in the flowering stage?


I've been “doing my own research” on nutrient compositions of various solutions used on cannabis plants in industry and in scientific papers. After all my reading I’m starting to wonder if the hype with high potassium concentrations at the flowering stage is bullshit. Let me be clear - when I say HIGH potassium concentrations I've seen people say to just drop nitrogen and phosphorus out of the equation and hit it with a high potassium dose - Not sure what ppm people are talking about.


Anyways I can’t really figure out if there really is any real merit to changing the nutrient solution. Here’s the paper that sent filled me with doubt: https://www.mdpi.com/2073-4395/12/5/1242

Don't know about the science but my plants love bat guano during flower.

Potassium is absolutely needed in flower for the plant's basic metabolic processes.

I’d like to hear the reasons why anyone would drop phosphorus during flower.

Manufactures like to convince people they need 14 different bottles of nutes on the shelf and it's led to a lot of nonsense being spread around.
I don't know much about nutes, but I think dropping phosphorus and nitrogen completely is nuts. High potasium definitely isn't necessary, plenty of growers here do just fine running the same mix start to finish.

Rubisco456 said:

... I've been “doing my own research” ... I've seen people say to just drop nitrogen and phosphorus out of the equation ...

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Most here on RIU won't recommend that - but I can suggest a sure fire way to continue your own research. Grow a crop without N or P as they suggest. Then grow another crop with N and P as most here on RIU suggest.

Note the differences.

Research complete.

Continue your "research" in your grow and get back to us. Run a couple clones with everything as close to identical as possible and don't feed potass

StareCase said:

Most here on RIU won't recommend that - but I can suggest a sure fire way to continue your own research. Grow a crop without N or P as they suggest. Then grow another crop with N and P as most here on RIU suggest.

Note the differences.

Research complete.

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This sounds too easy. I suggest we argue about stuff we have no experience with and find obscure articles online that support our claim. It is 2022 after all.

10ppm is plenty to sustain growth, but it doesn’t hurt to supply a little more. Optimal nutrients is ideal, but I believe that’s just being picky.

StareCase said:

Most here on RIU won't recommend that - but I can suggest a sure fire way to continue your own research. Grow a crop without N or P as they suggest. Then grow another crop with N and P as most here on RIU suggest.

Note the differences.

Research complete.

Click to expand...

ON IT!

I'm also running an experiment with 8-8-8-8-8-8-8-8-8-8-8 Macro and micro nutrient ratios.

I'd actually expect there to be a lot of salt stress if I did something like that.

Fallguy111 said:

Continue your "research" in your grow and get back to us. Run a couple clones with everything as close to identical as possible and don't feed potass

This sounds too easy. I suggest we argue about stuff we have no experience with and find obscure articles online that support our claim. It is 2022 after all.

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Yea once I get going I'm going to try some with low med and high and see what happens. maybe I'll post it in one of grow journal Threads.

Please sir, can I have some more. ... Npk

I saw article that suggests pHosphorous was mainly used up during the "stretch" of the flower stage.

hotrodharley said:

I’d like to hear the reasons why anyone would drop phosphorus during flower.

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phosphorous is key for root development. if you have enough roots then you can reduce the phosphrous, but not eliminate. grow the roots and then flower. You may want to lower phosphorous after the plant has started to bud. You can prune and defoliate to keep the plant vigorous without it needing to grow new roots which allows the extra energy stored within the roots to be added to the remaining branches.

BeastGrow said:

phosphorous is key for root development. if you have enough roots then you can reduce the phosphrous, but not eliminate. grow the roots and then flower. You may want to lower phosphorous after the plant has started to bud. You can prune and defoliate to keep the plant vigorous without it needing to grow new roots which allows the extra energy stored within the roots to be added to the remaining branches.

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It’s key for far more than root development. I wouldn’t dump a bunch in flower but I would definitely continue to supply it. I feed the same feed all the way from start to finish. I’ve also used Lucas formula using 3-part systems. Always get good results.

hotrodharley said:

It’s key for far more than root development. I wouldn’t dump a bunch in flower but I would definitely continue to supply it. I feed the same feed all the way from start to finish. I’ve also used Lucas formula using 3-part systems. Always get good results.

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I was on Earth Dust for a few grows, and not until I added a little Xtra phosphorus did I notice fatter buds .. don't think it's coincidence.

Week4@inCharge said:

... not until I added a little Xtra phosphorus did I notice fatter buds .. don't think it's coincidence ...

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It's not. Had good results with the regular feed - then started pulling chubbier bud with the PK boost.

click on nutrients (10:47)

"The first is the formation of inflorescences, paired with temporary, rapidly increasing elongation growth. Here the plant needs the highest amount of phosphorus in the flowering phase in order to produce enough inflorescences. Unripe fruits are the best choice for our FFJ, as they contain a high amount of oxalic acid. This organic acid is even better suited for dissolving phosphorus than sulfuric acid.. "

dank'd said:

click on nutrients (10:47)

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That's an interesting study. It's not what I'm seeing with my grows. Some strains will do ok with just a 4-4-4 feeding schedule throughout the whole grow, some will suffer. All dependant on strain. There's no magic recipe for all. In a healthy organic soil, the plant will grab what it wants, when it wants it. No guessing involved.

many studies have been done on tissue samples of plants in veg and flower and the levels of n and k are always higher than p in both phases by about 3-4 to 1

the u of u team recommends 20-10-20 full cycle as there is no need for more phosphorus, except, in the last 4-5 weeks of flower where as has been said the phosphorus has been depleted by stretch and also the buds themselves which are p sinks

so an amount of p can be added at that time to replenish the p taken from the fan leaves by the buds and the stretch. this to stop the fan leaves from showing deficiencies before reaching senescence and thus keeping the plant healthier up until ripeness