Question about Canna Stats

[BlazingTrees]

I use canna stats to figure out my nutrient profile. The other day I decided to check the math to see if it is correct...and I found that for N, they dont multiply by the mass percentage of N in NO3(22.58%), to give you the final ppm N...but they do multiply by the mass percentage K in K20, and the mass percentage of P in P205 to give you the final ppm of K and P. Is there a reason for this, or is the N number they give you on canna stats 4x what it should be?

 

[kaljukajakas]

There are some historical reasons why N-P-K ratios are actually N-P2O5-K2O ratios. It has to do with how nutrients were measured before modern analytic techniques became common. By that time everyone was using the NPK ratio to express the nutrient content of their fertilizers and the convention remained.

 

[BlazingTrees]

ahhh, I see. Thank you for the reply!

 

[Dee9]

There are some historical reasons why N-P-K ratios are actually N-P2O5-K2O ratios.

Good info kaljukajakas -

Hmm - I use to use an orchid fertilizer with the NPK ratio of 6-20-30.
On the back label the content was indicated as:
N 70g/kg
P 93g/kg
K 248g/kg

How are these to ratios related to each other?

Am I to understand that 6% of 70g/kg N is available to the plant - the same with 20% of the 93g/kg P and 30% of 248g/kg K?
Or am I mistaken?

 

[kaljukajakas]

Hmm - I use to use an orchid fertilizer with the NPK ratio of 6-20-30.On the back label the content was indicated as:
N 70g/kg
P 93g/kg
K 248g/kg

How are these to ratios related to each other?

Am I to understand that 6% of 70g/kg N is available to the plant - the same with 20% of the 93g/kg P and 30% of 248g/kg K?
Or am I mistaken?

They might have mixed something up or rounded some numbers incorrectly. Both values for nitrogen can't be right. The fertilizer must contain either 6% or 7% of N, which is the same as either 60 or 70 g/kg.

The values for P and K seem more or less ok. The fertilizer contains 20% of P2O5, of which 44% is actually P. So 0.2 x 0.44 x 1000g/kg = 88 g/kg P (close enough to 93). 83% of K2O is K so 0.3 x 0.83 x 1000g/kg = 249 g/kg of K.

 

[Dee9]

Hey kaljukajakas - thanks for the reply

You must spread some Reputation around before giving it to kaljukajakas again

I like your answers - no hocus-pocus - just math and fact!