Soil test phosphorus and potassium

Different laboratories use different chemical solutions, known as extractants, to determine soil test phosphorus (P) and potassium (K). These extractants lead to different soil analysis results on the same soil sample.

The current recommendations for soil testing in British Columbia are based on the Kelowna extractant, sometimes called the “Kelowna method.” If the lab you use follows a different method, their test results can be converted to equivalent results that would be obtained if the Kelowna method was used:

• Convert soil P and K test results to ‘Kelowna-equivalent’ results (Excel)

Results of soil testing should be used to determine the need for supplemental P or K for optimal crop growth. Consistent monitoring of crop growth, yield, and soil test results will aid in planning for P and K applications.

• Interpretations for Soil Test Phosphorus and Potassium: Guidelines for Southern British Columbia (PDF)