In a planted tank N does what exactly?
K does what?
and P, what ? yet again. I'm triing to better understand the ferts act with the plants. and more fine tune my tank situation as far a dosing
thanks

Look in the Barr Report Newsletter forum. There are individual articles that Tom has written about the different nutrients.

Nitrate causes leaf growth
Phosphorus encourages roots growth
Potassium encourages flower or fruit development

A lot, best to refer to Captain Bu's suggestion.
It's about 15 pages worth.

Regards,
Tom Barr