How should soil tests be interpreted for environmental purposes?

Current interpretations of soil test reports of Low, Optimum, High, were established based on the expected response of a crop to the nutrient being tested. Simply extending the interpretation levels for crop response to the potential for P loss has not been confirmed as a reliable approach. No direct relationship can be assumed to exist between the soil test calibration for crop response to P and the calibration for P loss in surface runoff. The critical soil test level for P loss may be above or even below the critical level for crop yield.

It is unlikely that there will be a simple critical soil test for P loss potential. A more integrated approach is likely, including many other site-specific factors to determine the environmental pollution potential of a field.