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:
- Very low: Minimal risk of P delivery to surface water. The Nebraska P Index does not include this level.
- Low: Current practices keep water quality impairment due to agricultural P pollution low.
- 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.
- 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.
- 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.