Proceedings available at: The phosphorus index is a risk management tool, designed to evaluate the potential for runoff from a field based on the conditions and management of that field. Based on many years of work with farms in Wisconsin, the author sees the P-Index as valuable tool for comparing fields and management on the same farm and influencing choices that will lead to the lowest risk of runoff. The tool should not be used to compare between farms, as differing management and geography can cloud those comparisons. Another aspect of the p-index that causes concern is its use as a regulatory tool. When the p-index is applied from a distance--without contact with the farm or farmer, a disconnect can develop.

1. Wisconsin ProducerWisconsin Producer
Perspective on thePerspective on the
Phosphorus IndexPhosphorus Index
Dennis R Frame
UW – Discovery Farms Program

2. P – Index (Management Tool)P – Index (Management Tool)
The P Index is a nutrient
management planning tool
It is also used as a targeting and
assessment tool for water quality
projects

3. P – Index (Management Tool)P – Index (Management Tool)
Excellent tool to evaluate the
relative risk of fields or
management practices against
other fields or practices on the
same farm

4. P – Index (Management Tool)P – Index (Management Tool)
Question the value of evaluating
the relative risk of fields or
management practices against
other farms

5. P – Index (Regulatory tool)P – Index (Regulatory tool)
Today the P-Index is a regulatory tool:
◦ Croplands, pastures, and winter grazing areas
shall average a phosphorus index of 6 or less
over the accounting period and may not
exceed a phosphorus index of 12 in any
individual year within the accounting period.

6. P – Index (Regulatory tool)P – Index (Regulatory tool)
The P-Index is an excellent regulatory
tool.
◦ It allows people with little background in
farming to calculate whether a farm is losing
phosphorus at unacceptable levels
◦ Agency personnel are making management
recommendations based on model, not based
on field visits, farmer contact or experience.

7. P – Index (Regulatory tool)P – Index (Regulatory tool)
The calculated impacts from changes in
management can be done in the office
with little or no involvement of the
farmer.
and
If we don’t like the results, just change
the criteria

8. P – Index (Regulatory tool)P – Index (Regulatory tool)
It is a goal of this project to prevent an
increase in the rotational PI of any field.
◦ Starting with Crop Year 2014, 50% of the
cropped acres used by participating farms must
meet a Phosphorus Index (PI) of 4 or less
throughout the rotation. Farms joining this
project as participating farms (non-emergency)
will be given 5 years to achieve this
requirement.

9. P – Index (Regulatory tool)P – Index (Regulatory tool)
Is there any data showing that reducing
the P-Index from 6 to 4 has reduced the
annual and total phosphorus loss as
measured in a water body?

10. Dry Run-17,792 acres,
27.8 sq. mi
South Fork (at Hwy
63)-21,312 acres, 33.3
sq. mi
North Fork (at Hwy
46)-53,376 acres, 83.4
sq mi
Total Watershed:
99,968 acres, 156.2 sq.
mi.

12. Willow River WatershedWillow River Watershed
Total of 17,522 acres
95% of all land (16,600 acres) had a soil test level below 50
ppm
11,000 acres (63% of all acres) had a PI of 1 or 2,
4,500 acres (25%) had a PI of 3 or 4
2,000 acres had a PI of 5 or greater, almost all was west of
Hwy 63

13. Willow River WatershedWillow River Watershed
This is a DNR target watershed with a TMDL (total
maximum daily load calculated)
Considering the implementation of an adaptive
management program:
◦ Need to reduce P loss by 0.25 lbs / acre
◦ Producers were asked to decrease their P-index by 0.25
lbs and told that the watershed would then achieve it’s
TMDL!

15. Producer PerspectiveProducer Perspective
The P-Index maybe the greatest tool every
designed if:
1. Agencies are held accountable that the
recommendations given to farmers will allow
them to remain profitable and water quality
will improve.

16. Producer PerspectiveProducer Perspective
The P-Index maybe the greatest tool every
designed if:
2. If water quality does not improve, the index
numbers cannot be adjusted until there is
sound science which proves that achieving the
new goal will improve water quality

17. Producer PerspectiveProducer Perspective
The P-Index maybe the greatest tool every
designed if:
3. All evaluation of improvement is based on the
model and not on water quality. Failure to
improve water quality is the agencies, not the
farmers.

18. The P-Index is a number,The P-Index is a number,
not actual loss!not actual loss!
2006 P Index
6.4
2007 P Index
1.3
2008 P Index
5.6
2006 Actual Loss
1.6
2007 Actual Loss
0.34
2008 Actual Loss *
6.3
4.4 lbs delivered in 7.5” rain