KH2PO4 vs. K2HPO4?

[beviking]

Mono Potassium Phosphate or Dipotassium Hydrogen Phosphate? Could you use the later for more potassium?

[beviking]

Apparently yes. Paul Sears wrote at thekrib "I use any of K2HPO4, KH2PO4 or H3PO4. The doses are so small that pH changes are negligible, whatever I use."
http://www.thekrib.com/Plants/Fertilizer/sears-conlin-feedback2.html

So unless anyone else has anything to add...?

[happychem]

Sure. In calculating how much is needed:

KH2PO4:
K - 22.73% by mass
PO4 - 69.79% by mass

K2HPO4:
K - 44.89% by mass
PO4 - 54.52% by mass

So for every gram of KH2PO4 you added to meet your PO4 requirement, you'd need to add 1.3g of K2HPO4.

Since it contains both more K by mass and you'd be adding more of it to start with, K2HPO4 would make a better incidental source of K than KH2PO4.

[beviking]

Since it contains both more K by mass and you'd be adding more of it to start with, K2HPO4 would make a better incidental source of K than KH2PO4.

Right, but since PO4 isn't dosed to much more than 1ppm, one would only be dosing ~.8ppm of K. Better than the .3 from dosing KH2PO4, AND you do away with that good for nothing extra H! :D

[happychem]

Absolutely! I think that K2HPO4 is the preferable choice, but I don't think that it makes any real difference in the long run.