Abject curiosity

[Hoovercat]

Had to drive for 3hrs. working today and a question occured to me. We provide all necessary nutrients for our plants in aquaria, but have to introduce K in high light environments since natural processes won't keep up. In nature, where does the necessary K come from? My sister has a B.S. in organic chem. so I'll hit her up and ask as well.

 

[7Enigma]

2 guesses I have.

1. The soil or water provides all the potassium needed since your dealing with a LOT more water/soil than a tank has. There's a lot more micro and macroorganisms dying constantly to replenish the nutrients. Rainwater might also be able to transport trace elements as well.

2. It doesn't. This is one of the limiting reasons why even in tropical regions where high light is plentiful the flora doesn't spread across the entire region in hours/days. I've heard/read something like the tropical rainforest soil is so depleted of nutrients (due to high light and ample water) that it stunts the growth of the plants. Makes sense since all the other main building blocks are in excess, somethings got to give...

 

[malkore]

I'm almost inclined to go with #2. I think there's enough K in nature, but you don't get huge forests of plants everywhere. In nature ,its survival of the fittest. In the aquarium, you are God and can manipulate 'reality' in the aquarium to grow plants unrealistically.

 

[newfound77951]

Potassium in natural waters comes mainly from the weathering of potassium-containing rocks such as mica and feldspar. So the natural concentration will vary somewhat with the local geology, but both of these minerals are very insoluble anyway, so almost all natural systems are low in K.

Rainforest soil is notoriusly poor in nutrients (hence the need for rotating, slash-and-burn agriculture) because, in a tropical system there is no need for storage of nutrients during the winter. Nutrients are constantly cycled through the biosphere, and dead material is recycled back into the system very quickly. It is quite likely that K could be a limiting nutrient in these systems. Interestingly, in marine systems, K is never considered to be a limiting nutrient, usually N, sometimes P or Fe are limiting.