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.