As I have it, plants only feed when they're in need of nutrients. They sometimes take up only a certain nutrient...or nutrients that they're in need of at that time.
They certainly don't feed all the time. That got me thinking. If I fertilize often...because i'm using a open soil, how much is actually taken up, and how much flows right through. Not a big deal really, but I would still like to know, and make the best of things. Dyna Gro ain't cheap
That's why I like to add a organic part (bark) to my mix...and zeolite to. It apparently holds onto nutrients for longer.
There's a lot of conflicting opinions on fertilizer. This thread has brought out some sensible sounding explanations but I have no idea whether any or all have been proven correct.
I am aware of the following:
A lot of nutrients are leached through the soil by water and so lost to our potted plants. This seems to be inevitable, even when using high CEC (organic or zeolite) in the mix. You may be able to reduce leaching but I don't think it is possible to eliminate and still provide the other conditions the plant needs.
Many plants may feed more than some understand. It is generally accepted that plants do not use nutrients in winter. A few years ago one of our leading bonsai growers recruited others all over Aust to trial winter feeding for pines. The results show much better health and growth when JBP are fed right through our winters. I now fertilize all evergreen plants (at reduced rates to compensate for slower growth) through winter. Efficacy may vary depending on how cold winter gets in any area.
Some plants appear NOT able to regulate uptake of nutrients. Proteacea family have evolved to live in low P soils and develop special roots that are super efficient at finding and mobilizing the little P available. If we provide 'normal' levels of P to these plants they overdose and die, indicating they have no mechanism to regulate uptake of P.
Plant nutrient references include symptoms of nutrient toxicity in plants. I'm not sure of the mechanism for such damage but plants can certainly be affected by excess or imbalance of nutrients.
I also follow the 'cheapest available nutrients' model. No point in paying high price when plants are only interested in the ions, not the source of them or how much you paid, and so much is just lost.
Flip side of this is that we need to also be aware of where those leached nutrients end up. Fertilizer leaching from our plants and gardens is implicated in waterway decline - algal blooms, fish kills, etc so we do need to reduce fert runoff as much as possible and make sure that runoff water is filtered as well as possible before ending up in drains.