1. Phosphorus Indices: an Understanding of Upper Mississippi Strategies John A. Lory, Ph.D. Division of Plant Sciences University of Missouri

2. Outline Overview  Phosphorus indexes: why do we need them?  Does it make sense that every state is different? Missouri P index  Our objectives.  What you need to make it work.

3. Many streams and lakes are phosphorus limited. Jones and Knowlton 1993 Water Clarity as measured by Secchi depth (m) Missouri reservoirs

4. Challenge: Where, when, and how to apply manure to minimize P loss to surface water.

5. Runoff volume Method of application Time since application Application rate Soil test P Soil type Cultivation Vegetative cover Factors affecting runoff of P

6. Nutrient planners are required to assess phosphorus loss on all fields receiving manure.

7. You choose the method Agronomic soil test recommendation  Objective: does the crop need P? Phosphorus threshold Phosphorus Index  Objective: will applied P be vulnerable to losses?

8. Low N-based Applications Medium N-based Applications High P-based Applications Very High No Manure Applications Phosphorus Assessment

9. Assessment tools are state specific. Index Target: - Runoff - Irrigation - Runoff - Irrigation Long-term Runoff - Runoff - Leaching

10. Assessment tools are state specific. Approach: Multiplicative tabular factors Simplified model Additive tabular factors Simplified model

11. Do Differences Between States Make Sense?

12. Missouri’s approach: 2 choices Agronomic soil test recommendation  Objective: does the crop need P? Phosphorus threshold Phosphorus Index  Objective: will applied P be vulnerable to losses?

13. Missouri P index objectives Strategic planning tool for use in writing a 5-year nutrient management plan. Identify fields where field characteristics are likely to result in high P loss in runoff. Simple to use with readily available information for people with an NRCS conservation plan.

14. 6 Factors in the Missouri P index Soil test result  include units and sampling depth Tillage  Tilled vs. notill and forages RUSLE estimate of erosion Land cover Soil hydrologic group  A, B, C or D Distance from water feature

15. Simple model approach Sediment P  Function of RUSLE-2 erosion, soil test P and sediment delivery ratio. Soluble P  Function of runoff volume (curve number approach and soil test P).

16. Higher standard in the clear-water region of the state.

17. P index rating system RatingClear-water region Other Low<1 <3 Medium>1 and 3 and <7 High>5 and 7 and <12 Very High>10 >12

18. 6 Factors in the Missouri P index Soil test result  include units and sampling depth Tillage  Tilled vs. notill and forages RUSLE estimate of erosion Land cover Soil hydrologic group  A, B, C or D Distance from water feature

19. Surface applications require a tactical tool. Educational tools being developed to identify times of year runoff least likely Inputs:  Ground cover- County  Soil hydrologic group- Soil condition  Soil moisture Output  Evaluation of runoff risk (low, medium, high)  Predicted rainfall amount needed to initiate runoff

20. P index developed cooperatively by MU and NRCS. Based on best professional judgment. Available as a spreadsheet at: http://nmplanner.missouri.edu/

21. Future P index integrated into RUSLE 2 Email notification system to help evaluate timing of manure applications.