The “summation exceeds 100%” error usually occurs when nitrogen (N) values are entered incorrectly. The Cool Farm Platform (CFP) expects nitrogen in three specific forms:
% N (as ammonium-N, NH4-N)
% N (as nitrate-N, NO3-N)
% N (as urea-N)
Important: these fields expect the nitrogen content, not the total mass of the compound itself.
If your fertiliser label gives nitrogen as compounds (e.g., ammonium (NH₄), nitrate (NO₃), urea), you need to convert them to nitrogen content before entering them into the tool.
| Compound | Conversion Factor | Example (20% compound) | Enter as |
|---|---|---|---|
| Nitrate (NO₃) | 0.22 | 20% × 0.22 = 4.4% N | nitrate-N |
| Ammonium (NH₄) | 0.7765 | 20% × 0.7765 = 15.5% N | ammonium-N |
| Urea (CO(NH₂)₂) | 0.46 | 20% × 0.46 = 9.2% N | urea-N |
✅ Tip: Always enter N-equivalents in the three fields - this ensures the total stays below 100% and prevents the error.
If you enter the compound percentage (e.g., 20% NO3) instead of the nitrogen content, the tool interprets this as 20% nitrogen and then internally converts it to the corresponding compound mass.
Because the compound (e.g. nitrate) is heavier than nitrogen, the calculated total compound mass can quickly exceed 100%, especially when more than one nitrogen form is present.
N Source | % | Conversion | Calculated "compound mass" |
Nitrate-N | 20% | ÷ 0.22 | 90.91% |
Ammonium-N | 15.5% | ÷ 0.7765 | 20% |
Urea-N | 9.2% | ÷ 0.46 | 20% |
Total = | 130.91% |
⚠️ Note: Users do not need to do this N → Compound calculation - it’s shown here only to illustrate why entering total compound percentages causes the summation error. Focus on entering N-equivalents as shown in the previous table.
P can be entered as % P or % P₂O₅
K can be entered as % K or % K₂O
No conversion is needed for P/K in this context - the main source of the summation error is nitrogen mis-entry.
Enter nitrogen as N-equivalents in the three tool fields: ammonium-N, nitrate-N, urea-N.
Convert compound amounts from your fertiliser label using the compound → N factors above.
Ensure the total of %N + %P + %K stays below 100%.
If unsure, send a photo or screenshot of your fertiliser label - we can help determine the correct N-equivalents to enter.