This blog is part of an ongoing knowledge sharing activity of the Haifa Group Modern Greenhouses special task force.
A frequent question I get from growers is how come potassium nitrate 13-0-46 = 59% and not 100%
Nutrients content
I’d like to start with a basic explanation about the NPK nutrients and their percentages (%) in fertilizer formulae.
Fertilizer's formula usually refers to the content of nutrient in their oxide forms (N-P2O5-K2O). In Scandinavia, Australia and South Africa it is more common to refer to elemental forms (N-P-K).
For example: |
So how we sum to 100% ?
Here we have to consider the actual form of the nutrients in the fertilizer:
In mineral fertilizers, nitrogen may be present as ammonium, nitrate or amide (urea), phosphorus is present mainly as phosphate, and potassium is present as K+ ion. The following table shows the ratios between elements, oxides, and the forms mentioned above.
Ammonium | NH4 = | N x 1.28 |
|
Nitrate | NO3 = | N x 4.43 |
|
Amide | (NH2)2CO= | N x 2.14 |
|
Phosphate | H2PO4= | P x 2.68 | P2O5 x1.15 |
Potassium | K = | K x1 | K2O x 1.2 |
Now, 13% N as NO3 means that 13x4.43= 57.6% of the product is NO3 |
Not 100% yet….
The difference is attributed to
- The fact that the actual analysis is somewhat higher than 13-0-46
- Presence of trace impurities in the product
- Moisture
Premium Multi-K™ products such as Multi-K™ GG and Multi-K™ Reci contain higher analysis, and less impurities. For actual analyses see product data sheets.
Pure Element | Multiply by | Oxide form | Multiply by | Pure Element |
|---|---|---|---|---|
N | 4.426 | NO3 | 0.226 | N |
N | 1.288 | NH4 | 0.776 | N |
P | 2.292 | P2O5 | 0.436 | P |
K | 1.205 | K2O | 0.83 | K |
Ca | 1.399 | CaO | 0.715 | Ca |
Mg | 1.658 | MgO | 0.603 | Mg |
S | 2.996 | SO4 | 0.334 | S |
S | 2.497 | SO3 | 0.4 | S |
This blog is part of an ongoing knowledge sharing activity of the Haifa Group Modern Greenhouses task force.