Non orchid potassium toxicity data

[Rick]

So as a tutorial of things that confound toxicology issues to make things as complex as possible I'll summarize my potassium toxicity studies for the last 5 years.

Acute LC50 is 50% mortality after 96 hours
Chronic IC25 is a 25% reduction in growth or reproduction after 7-28 days (depends on species).
Each species was tested in a range of hardness from 100 to 400 ppm (as CaCO3) So calcium ranged from about 25 to 100 ppm (but there was magnesium in the mix too, and we varied the Ca/Mg ratio to minimal effect).

So from most to least sensitive:

Mussel LC50 = 41 to 95 mg/L K very strong Ca effected LC50 relationship
Hyallela LC50 = 221 mg/L K (200 hardness tested only)
Ceriodaphnia (water flea) LC50 = 312 to 458mg/L good Ca effecte LC50
Ceriodaphnia 7 day IC25 = 166mg/L (200 mg/L Hardness tested only)
fathead minnow LC50 = 459 - 588 mg/L weak or no Ca effected relationship
fathead minnow 28 day IC25 = 189mg/L (200 mg/L hardness tested only)
Carp LC50 = 437 mg/L (200 hardness tested only)
Midge LC50 = 2696 - 3097 mg/L (no relationship to hardness)
Midge 21 day IC25 = 546mg/L K (only tested at 200mg/L hardness).


Note the wide range in sensitivties (41 to 3097mg/L) for short term lethality for 6 species.
Also note the big difference between what kills versus what inhibits.

I have not had the opportunity to run chronic inhibiton tests with freshwater mussels, but some work done in 1973 indicated that the value could be as low as 10 mg/L K

 

[Rick]

Keep in mind that I have never come across a natural freshwater surface body or well water that had more than 40-50 ppm K.

And none with musels in it over 10 ppm.

The US nationional average is around 5ppm I believe. Places where it runs higher are generally contaminated with fertilizer runnoff, mining wastes, or petrolium production wastes.

 

[Rick]

So given the above results of only 6 species and limited test conditions, you may discern that understanding orchid toxicity/nutrition requirements of K will also not be obvious (for 30,000 species, 150,000 hybrids, and all combinations of NPK Ca Mg S, HCO3.....).

The bottom line for protection of stream organisms is to just use the most sensitive organism as the canary in the coal mine.

All organisms require some potassium for metabolic activities (including mussels). But even though the midges can handle 500ppm of K chronically, they grow just fine at less than 5ppm (like the mussels).

 

[gonewild]

Interesting.

Probably if you look hard enough you'll find some in house documents dating from the 50's where Rockafeller invested heavy in Potassium mines and paid off some scientists to exaggerate it's importance and amounts needed in agriculture. As I said before most of what we believe we need to consume is driven by somebody convincing us we need it and then telling us using twice as much is better.

Then we can buy something else to offset the problems caused by the first stuff.

We should all believe what we know and not what we are told.
(except what Rick tells us about K-lite!)

 

[Rick]

Interesting.

Probably if you look hard enough you'll find some in house documents dating from the 50's where Rockafeller invested heavy in Potassium mines and paid off some scientists to exaggerate it's importance and amounts needed in agriculture.

I wouldn't go so far as that. There is are Potassium Association, but there is also a lot of good research to just plain old compute yeild/demand based on residual soil concentrations of K in a field and how much gets sucked up in various strains of corn wheat ... primary food crops. Farmers really don't want to pay for more than they need to. But when it comes to orchid fanatics, they're like Italian or Jewish Moms (EAT, EAT, EAT!!!)

(except what Rick tells us about K-lite!)

Whoa that's a lot of responsibility Lance. That's going to take a lot more beer:wink:

 

[keithrs]

Whoa that's a lot of responsibility Lance. That's going to take a lot more beer:wink:

You better skip the beer and go straight to the hard stuff!oke:

 

[Rick]

You better skip the beer and go straight to the hard stuff!oke:

I know where a couple of active stills are out in 'them thar hollers'!

 

[gonewild]

Hope their mash is not over 10 ppm K.

 

[Rick]

Hope their mash is not over 10 ppm K.

Good TN spring water, but probably lots of K goodness in the corn mash!

The distillation process should be good enough for all the "medicinals" to be present!

 

[abax]

I didn't understand a word that anybody said,but I'm glad I read it anyway.

Hey there, TN feller, you'd be better advised not to mention said stills. In
KY you can get shot for that, you know!

 

[gonewild]

I didn't understand a word that anybody said,but I'm glad I read it anyway.

Hey there, TN feller, you'd be better advised not to mention said stills. In
KY you can get shot for that, you know!

What's a still?
:drool:

 

[cnycharles]

better be careful about going and surreptitiously checking out someone's evaporative medicinal units out in the woods; people can get ornery about woodland visitations.
a former co-worker was telling me about reading in an old journal where someone had a wild ginseng patch out in nowhere, and someone kept poaching it. the owner got fed up and set up a double-barreled deterrent, and a bit later upon checking out his patch discovered that someone had tripped the deterrent and had not left the premises. it ended up that the visitor was quietly interred, and nobody ever went about trying to find out 'where johnny went to'.... so the person must have been a bit of a rascal and wasn't missed...

 

[Rick]

I didn't understand a word that anybody said,but I'm glad I read it anyway.

Hey there, TN feller, you'd be better advised not to mention said stills. In
KY you can get shot for that, you know!

Just be courteous and leave a stick on the fire.