If a fertilizer analysis is 13-13-13 on an oxide basis, what is the analysis on an elemental basis?

To convert the fertilizer analysis from an oxide basis to an elemental basis, it’s important to understand how the nutrients are represented. In the 13-13-13 analysis, the numbers correspond to the percentages of nitrogen (N), phosphorus (P₂O₅), and potassium (K₂O) respectively, expressed as oxides.

When converting phosphorus and potassium from oxide forms to their elemental forms, you need to apply specific conversion factors:

1. For phosphorus pentoxide (P₂O₅), the conversion to elemental phosphorus (P) typically uses a multiplier of 0.44. This means that for every unit of P₂O₅, there are approximately 0.44 units of P.

2. For potassium oxide (K₂O), the conversion to elemental potassium (K) uses a multiplier of 0.83. Thus, for every unit of K₂O, there are about 0.83 units of K.

Applying these conversions to the 13-13-13 analysis:

• The nitrogen content remains the same at 13% because it is already expressed in elemental form.

• For phosphorus, the conversion from 13% P₂O₅ would be 13% (P₂O