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July 17, 2002 "Refinement and Application of the Wisconsin Phosphorus
Index"
July 17, 2002 Roundtable Minutes
Conclusions & Resolutions
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Wisconsin has a functional phosphorus index (PI).
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The current PI is not a final product - revisions, updates, and additions
are planned.
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The current PI is better at estimating particulate phosphorus (PP)
losses than soluble (SP) losses.
Issues to Resolve
- Other P.I.s may weigh too heavily on the effectiveness of buffers
in reducing P loads to surface waters.
- Project needs linkages to limnologists.
- Need to form four to six broad groupings of Wisconsin soils based
on total P (TP) - soluble P (SP) relationships. These will be input
parameters for the PI.
- Standardized tests for total P (TP) or the development of conversion
factors among the various extractants used to measure TP.
- Standard tests for soluble P (SP) in manure.
- Is current topographical data used by nutrient management planners
adequate for PI models? Also is this data readily available to planners.
Research & Information Needs
- Additional field calibration of the P.I.
- Data for revision and update of the P.I.
- Further investigation of the sediment and P trapping abilities of
buffers.
- Study of the physical characteristics of effective buffers.
- Buffer discussion at future Roundtable meeting
- Investigate the impact of fall manure applications on P losses and
P.I. calibration.
- Explore the possibility of a multi-state P.I.
- Collaborations with Iowa State University and University of Minnesota
- Apply the P.I. on various larger scales (watersheds, etc.).
- Collect data on the P content of sand, silt, and clay particles as
a function of soil series.
- Develop soil test P (Bray 1) and soluble P relationships (calibrations)
for additional Wisconsin soils.
- Conduct simulated runoff experiments on other rotational crops grown
in Wisconsin.
- Investigate the seasonal losses of SP from vegetation (esp. freeze-thaw
losses).
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