Interpretation of P Loss Ratings

Phosphorus index scores are generally classed into four or five risk levels regarding impact of P loads on eutrophication of water resources. Interpretation of risk levels generally suggests some management options.  The risk levels and interpretations may be similar to the following:

  1. Very low:  Minimal risk of P delivery to surface water.  The Nebraska P Index does not include this level.
  2. Low:  Current practices keep water quality impairment due to agricultural P pollution low.
  3. Medium:  Delivery of agricultural P may cause some water quality impairment, and consideration should be given to alternative conservation and P management practices.  Manure can be applied at rates sufficient to meet crop N needs.
  4. High:  Phosphorus loss from the field causes much water quality impairment.  Remedial action, such as alternative conservation measures or P management practices, is required.  Manure can be applied, but P applied should not exceed crop P removal.  Manure can be applied to meet a crop’s N need, but total P applied in one or more applications made in a four-year period should not exceed crop removal during that four-year period.
  5. Very high:  Impairment of water quality is extreme, and remedial action is urgently required.  Manure application should be discontinued.  Improved conservation measures should be implemented.