Soil Erosion and the Phosphorous Index
Posted: October 2, 2014
One of the required transport factors for completing the P Index is soil erosion calculated using the Revised Universal Soil Loss Equation (RUSLE). Beginning October 1, 2014 with the release of Version 8.0 of the Nutrient Management Program Technical Manual (October 2014), soil loss numbers from NRCS Conservation Plans or Ag E&S Plans developed using PAOneStop can be used in the P Index. Specifically, Appendix 5: Phosphorous Index of the Technical Manual states:
“The erosion rate estimates soil loss based on crop management, tillage practices, regional location, and best management practices. The erosion value for the P Index is calculated using the Revised Universal Soil Loss Equation (RUSLE) and is reported in tons/acre/year. This is usually determined by Pennsylvania USDA-NRCS as a part of the conservation plan development process. For operations that do not have a Conservation Plan, the PAOneStop Farm Mapping and E&S Planning System (https://www.paonestop.org/) can be used to determine soil loss values for use in the P Index.”
“For the P Index, the actual (A) erosion value should be used and not the tolerable (T) soil loss value. However, if the conservation plan is fully implemented to meet T then the T soil loss value can be used in the P Index.”
For Act 38 Nutrient Management Plans (NMPs), both the plan writer and plan reviewer must verify that a current Ag E&S Plan is in place. During the planning process and also during the plan review on-site visit, both the planner and reviewer should ask to see a copy of the Conservation Plan or Ag E&S Plan used for the P Index soil loss numbers.
For Nutrient Balance Sheets (NBSs) that are using Option 3 and are part of the NMP, the soil loss numbers must be calculated under the P Index guidance outlined above for NMPs. In this situation, both the plan writer and plan reviewer must verify the soil loss numbers from the importer’s Conservation Plan or Ag E&S Plan. In this situation, it may be advantageous for the plan writer and/or the NMP operation to have a copy of the soil loss calculation, in which RUSLE was used, so the plan review is not delayed due to the reviewer needing to track down the information.
Plan reviewers are authorized to ask or verify with the plan writers and NMP operations where the soil loss numbers came from, and additionally ask for documentation. Plan reviewers do not need to verify a Conservation Plan or Ag E&S Plan for every importer, due to time issues, but they are directed to make sure that all numbers used in NBS development are true and accurate.
- Director of Nutrient Management & Odor Programs, State Conservation Commission