Transcript Status on Use of the P Index Fundamentals of Nutrient

P Index
Fundamentals of Nutrient Management Training Course
December 15, 2005
Isaac Wolford, West Virginia NRCS State Agronomist
WHAT IS THE P (PHOSPHORUS)
INDEX ?
The P index quantitatively determines the
relative risk of P movement from a given
field by considering most of the factors that
govern P losses.
WHAT IS THE P (PHOSPHORUS)
INDEX ?
The Phosphorus Index (P Index) is a tool that can identify
farm fields that are a potential source of phosphorus (P)
pollution of surface waters.
Using the P Index can help a farmer identify fields and
management practices that have the greatest potential to
pollute bodies of water with phosphorus.
What does Phosphorus Index
Do?
PHOSPHORUS INDEX
COMBINES THE EFFECT OF
SOURCE
FACTORS
TRANSPORT
FACTORS
What does Phosphorus Index
Do?
SOURCE
FACTORS
Soil Test P
Source, Method, Rate, Timing of P
TRANSPORT
FACTORS
Soil Erosion
Site Vulnerability
Site vulnerability to P-loss as a function of Total P Index
rating values
Site vulnerability rating Total P Index rating value
Low
<8
Medium
8 to 14
High
15 to 32
Very High
>32
Site Vulnerability
Low to medium site vulnerability ratings indicate that current
management practices are adequate for protection of surface
waters from phosphorus pollution.
High and very high site vulnerability ratings indicate a need
for improved management practices.
Phosphorus Concerns Leading
To The Index Use
Annual application of
phosphorus exceeding its
removal by crops.
Phosphorus
accumulation in soils
leads to high soil test
values for phosphorus.
Movement of phosphorus
from crop fields into
bodies of water may lead
to excessive growth of
algae (algal bloom).
Phosphorus Concerns Leading
To The Index Use
Thus, algal bloom caused by phosphorus movement to a body of
water leads to reduction of oxygen in water.
However, most P initially added to land through fertilizer or manure
reacts with soil components, converting to an insoluble form or
attaching to soil particles.
Thus, most P loss in agriculture is associated with loss of soil
particles.
The West Virginia Situation
Currently in West Virginia, there are no state
nutrient management regulations.
This presentation focuses on requirements as they
relate to USDA NRCS Nutrient Management
Standard (590).
Recent CAFO Management rules have referenced
the use of the 590 Standard.
The West Virginia Situation
Use of the 590 Standard is limited to USDA
programs and CAFO management plans (As
outlined in the CAFO permit rules).
Surrounding states have adopted a
phosphorus index.
Each state has a different type of
phosphorus index.
There is discussion on standardizing the P
Index in the East.
NEW FOR 2005
 The latest version of RUSLE2 contains a
Nitrogen Leaching Index.
 The Index number can be applied to the
existing scale.
RUSLE2 N LEACHING INDEX
N Leaching Index
LEACHING INDEX NUMBER
INDEX NUMBER BY SOIL TYPE
National Phosphorus
Management Options
Phosphorus Application Option 1
The Phosphorus Index
P INDEX RATING
P APPLICATION
Low Risk
Nitrogen Based
Medium Risk
Nitrogen Based
High Risk
Phosphorus Based
CROP REMOVAL
Very High Risk
Phosphorus Based
NO APPLICATION
Phosphorus Application Option 2
The Phosphorus Threshold
Soil P Threshold Level
P APPLICATION
< ¾ TH
Nitrogen Based
= > ¾ TH, < 1 ½ TH
Phosphorus Based
CROP REMOVAL
= > 1 ½ TH, < 2 TH
Phosphorus Based
½ CROP REMOVAL
= > 2 TH
Phosphorus Based
NO APPLICATION
Phosphorus Application Option 3
Soil Test Phosphorus
Soil Test Phosphorus Level
P APPLICATION
LOW
Nitrogen Based
MEDIUM
Nitrogen Based
HIGH
Phosphorus Based
1½ TIMES CROP REMOVAL
VERY HIGH
Phosphorus Based
CROP REMOVAL
EXCESSIVE
Phosphorus Based
NO APPLICATION
Status of the P Index in
West Virginia
West Virginia has utilized a P Index
within the 590 standard since the
mid-1990s.
The P Index has remained unchanged
since its inception.
The Current P Index in
West Virginia
The current P Index is only utilized in
a five county area in the Potomac
Valley of West Virginia.
Statewide Standard
 Manure or litter may be applied at the nitrogen
based application rate when soil test
phosphorus levels are low to medium.
 If the current soil test indicates the soil
phosphorus level is high, a phosphorus based
application rate of up to 1.5 times the crop
removal rate will be used.
 If the phosphorus level is very high, greater than
80lbs/ac, manure or litter may be applied at the
crops estimated phosphorus removal rate.
Statewide Standard
 If the phosphorus level is less than 120 lbs., a single
application of phosphorus applied as manure may
be made at a rate equal to the recommended
phosphorus application or estimated phosphorus
removal in harvested plant biomass for a maximum
period of 3 years. When such application is made
the nitrogen application rate will not exceed crop
needs during the year of organic fertilizer
application.
Phosphorus Field Risk Assessment
(Potomac Valley SCD)
 When animal manures or other organic by-
products are applied and the current soil test
indicates the soil phosphorus level is very high,
greater than 80lbs/ac, a field-specific assessment
of the potential for phosphorus transport from the
field shall be completed.
Phosphorus Field Risk Assessment
(Potomac Valley SCD)
 For fields with high or very high potential
losses, appropriate conservation practices
identified in the Phosphorus Index must be
installed to reduce the vulnerability to offsite phosphorus transport.
 A record of the assessment rating for each
field or sub-field, and information about
conservation practices and management
activities that can reduce the potential for
phosphorus movement from the site, will be
included in the plan.
THE END
QUESTIONS?