Please verify: calculating the real NPK

I posted this in another thread, but I need confirmation that my info is correct.

Please someone correct me if I'm wrong, because it applies not only to BioBizz NPK.

The percentage of P and K is not what it says on the bottle, it has to be calculated, this is because:
P2O5 consists of 56.4 % oxygen and 43.6% elemental phosphorus.
K2O consists of 17% oxygen and 83% elemental potassium.
Example: the percentage is 83% for K, so K= 0.83 * K2O.




BioBizz Grow NPK(as written on the bottle): 8 - 2 - 6:

N 8% = 4% ammonium-Nitrogen + 4% nitrate-Nitrogen (=8% N)
P 2% = 0.87 % P
K 6% = 4.98 % K

Conclusion: GROW is 8 - 0.9 - 5 (or 1 - 0.1 - 0.6)


BioBizz Bloom NPK (as written on the bottle): 2 - 6 - 3.5:

N 2%: 0.9% ammonium-Nitrogen + 1.1 % nitrate Nitrogen (=2% N)
P 6%: 2.62% P
K 3.5%: 2.91% K

Conclusion: BLOOM is 2 - 2.6 - 2.9 (or 1 - 1.3 - 1.4)

The % listed usually states the % of the elemental quantities in the bottle too, dont think Biobizz do, but ignore their labels anyways as they could never be that accurate.

Biobizz is made from the leftover sludge that comes from making mollasses, so unless they test every batch to check the NPK well then they're just guesstimating.

BioBizz is not what this thread is about, so I bump:

Is my method of calculating P and K correct?

Just for your information, it is correct. But only if the P and K sources are stated as K2O and P2O5 on the bottle (small print).

However, it doesn't really matter for most (it seems) - only for those with curiousity beyond making a harvest.