Rick
Well-Known Member
How come there is so much K in plants when K is generally less common in the environment than Ca or Mg?
A lot of fertilizers are based on what is typically found in plants with the logic being that if that is what's in a plant then that must be what it needs, so supply it in the same ratio.
However most plants (certainly in the wild) do not access soil or aquatic systems that have high potassium levels (unless they are robbing it directly from adjacent plants). But they seem to be very efficient at uptaking and sequestering the nutrient. This also applies to materials that have ionic exchange capacity.
generally calcium and magnesium are more abundant in soil/water substrates than K (especially on limestone cliffs). But the orchids we culture from these sites generally get fertilizer mixes that have more K available than Ca or Mg.
I'm proposing a notion that poor growth in our "calcareous" paph species or fast/big growing multis is not due to Ca or Mg deficiency (per se) but by K overdose (which causes Ca and Mg deficiency).
I would also conjecture that calcerious (or calciolus) species do not have a special Ca or Mg need, as opposed to an extra sensitivity to K.
This is similar to the work I'm doing with freshwater mussels. For some reason they can suck K up more efficiently than other fresh water organisms, but they seem to be unable or very inefficient at eliminating from their systems (relative to other freshwater organisms). Subsequently, their internal body burden goes up higher (to toxic levels) than other critters and die.
It could be that many of our favorite orchids coming from K impoverished systems are similarly extra good at sucking up K, and when given fertilizers with all that K (and inadequate Ca and Mg to offset) that they get overloaded with K and die from what look like Ca or Mg deficiencies.
A lot of fertilizers are based on what is typically found in plants with the logic being that if that is what's in a plant then that must be what it needs, so supply it in the same ratio.
However most plants (certainly in the wild) do not access soil or aquatic systems that have high potassium levels (unless they are robbing it directly from adjacent plants). But they seem to be very efficient at uptaking and sequestering the nutrient. This also applies to materials that have ionic exchange capacity.
generally calcium and magnesium are more abundant in soil/water substrates than K (especially on limestone cliffs). But the orchids we culture from these sites generally get fertilizer mixes that have more K available than Ca or Mg.
I'm proposing a notion that poor growth in our "calcareous" paph species or fast/big growing multis is not due to Ca or Mg deficiency (per se) but by K overdose (which causes Ca and Mg deficiency).
I would also conjecture that calcerious (or calciolus) species do not have a special Ca or Mg need, as opposed to an extra sensitivity to K.
This is similar to the work I'm doing with freshwater mussels. For some reason they can suck K up more efficiently than other fresh water organisms, but they seem to be unable or very inefficient at eliminating from their systems (relative to other freshwater organisms). Subsequently, their internal body burden goes up higher (to toxic levels) than other critters and die.
It could be that many of our favorite orchids coming from K impoverished systems are similarly extra good at sucking up K, and when given fertilizers with all that K (and inadequate Ca and Mg to offset) that they get overloaded with K and die from what look like Ca or Mg deficiencies.
