[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


I've wondered if it might be useful to think in terms of ratios when dosing
NPK. To that end, I asked one of the list botanists what ratio these
elements were found in plant tissue. He answered:

"An average N:P:K ratio, based on the composition of leaves, would be about

Then I asked a list chemist to help me with the math to get to that ratio:

N - KNO3 MW=101 g/mol N=14%
P - NaH2PO4 (Discus Buffer) MW=120 g/mol P=26%
K - K2SO4 MW=174 g/mol K=44%

KNO3 =26/14x16=30, MSP=1, K2SO4=26/44x8=4.7, so you would add these
in a 30:1:5 (roughly) ratio to get a 16:1:8 N:P:K ratio."

Is it just me, or does that calculation not account for the K in the KNO3?
So, if I mixed a powder of the compounds above, in the ratio shown above,
and set the dosing level by measuring N (or NO3), then I should be able to
provide these nutrients in the right ratio. I suspect that I can delete the
P since I feed heavily.

Any thoughts?

Tom Wood
Austin, Texas