Transcript Phosphorus in the Environment

Phosphorus Index
Based Management
Douglas Beegle
Dept. of Crop and Soil Sciences
Penn State University
[email protected]
http://panutrientmgmt.cas.psu.edu
Why do we need a P Index?
Why not just agronomic recommendations?
¼
Feed
Crops
Soil
Animals
Nutrient
flows in
modern ag
?
Nitrogen Based
Corn/Dairy Manure
¾
N
P Index
P2O5
K2O
P Index
Manure
Phosphorus Based
Corn/Dairy Manure
Eutrophication
Regional P Balance
N
P2O5
K2O
Field P Balance
P Index
Critical Source Area Management
• Overlap of Source & Transport Indicators
• Identify and manage the critical source areas
• Evaluate environmental risk
• Target effort and resources
Critical Source Area
Source
Transport
Critical Areas of P Export
90% of annual P export comes from 10% of land area
90% of P Loss comes from
10% of the watershed
Mahantango Creek Watershed,
USDA-ARS
Managing Phosphorus Pollution
Transport
Sources
NPK
Runoff
Erosion
Leaching
Tile flow
Subsurface
flow
Hydrology
Soil Test vs P Loss
2.4
P loss,
lb P2O5/A
1.6
P Threshold
No recent P
inputs
Crop P
Optimum
0.8
R2=0.80
0
0
200
400
600
800
Mehlich-3 soil P, mg/kg
Sharpley, USDA-ARS
Managing Phosphorus Pollution
Transport
Sources
NPK
Runoff
Erosion
Leaching
Tile flow
Subsurface
flow
Hydrology
Soil Test vs P Loss
- with applied P
2.4
P loss,
lb P2O5/A
75 kg P/ha TSP
For all data points
R2=0.40
1.6
0.8
112 kg P/ha swine
slurry
150 kg P/ha
poultry manure
Soil Only
R2=0.80
0
0
200
400
600
800
Mehlich-3 soil P, mg/kg
Sharpley, USDA-ARS
Phosphorus Index
• P Source Site Characteristics
– Environmental Soil Test P
• Same soil test different interpretation
• Sampling Questions?
• P Saturation?
– P Fertilizer
• Rate and Appl. Method
– Organic P
• Rate and Appl. Method
• P Source Coefficient (PSC)
– Direct availability of manure P to runoff
– Based on WEP in manure
Managing Phosphorus Pollution
Transport
Sources
NPK
Runoff
Erosion
Leaching
Tile flow
Subsurface
flow
Hydrology
Phosphorus Transport by Erosion
6
Total P
mg/L
4-
Conventional
till wheat
2 - Converted
to no-till
0
1980
Erosion reduced 95%
1985
1990
1995
Sharpley, USDA-ARS
Managing Phosphorus Pollution
Transport
Sources
NPK
Runoff
Erosion
Leaching
Tile flow
Subsurface
flow
Hydrology
Zone of Interaction with Runoff
 Location of applied
P
 Interaction with
runoff
• P on surface
• Soil test at surface
• High P Saturation at
surface
Psat = P / Al + Fe
Oxalate extr. or Mehlich
3 extr.
Algal-available P, mg/L
Soluble P Transport in Runoff
1.0
Converted
to no-till
0.5
0
1980
1985
1990
1995
Conventional
till wheat
Sharpley, USDA-ARS
Managing Phosphorus Pollution
Transport
Sources
NPK
Runoff
Erosion
Leaching
Tile flow
Subsurface
flow
Hydrology
Soluble P Loss by Sub-surface flow
Very Dependent on soil
properties
– Hydrology
• Piston flow
• Macro pores
– Texture
– Soil Chemistry
(Fe, Al, Ca)
– P loading/saturation
Data from: Bolton et al., 1970
Culley and Bolton, 1983
– Artificial Drainage
P Loss is a Complex “Landscape” Process
Transport
Sources
NPK
Runoff
Erosion
Leaching
Tile flow
Subsurface
flow
Hydrology
Landscape Transport
Distance
Runoff Return Period
Hydrology
Modified Connectivity:
Modified Connectivity:
Riparian Buffer
Direct Connection
Phosphorus Index
• P Transport Site
Characteristics
Erosion
– Soil Erosion
– Runoff Class
Runoff
Drainage
– Leaching Potential
• Sub-surface Drainage
– Contributing Distance
– Modified Connectivity
Distance
Field ID
PA
Is the CMU in a Special Protection Watershed?
Is there a significant farm management change as defined by Act 38?
Is the Soil Test Mehlich-3 P greater than 200 ppm P?
Is the contributing distance from this CMU to water less than 150 ft.?
If the answer is yes to any of these
questions Part B must be used.
Field ID
PART B: SOURCE FACTORS
Phosphorus
Index
SOIL TEST
Mehlich-3 Soil Test P (ppm P)
Soil Test Rating = 0.20* Mehlich-3 Soil Test P (ppm P)
FERTILIZER P
RATE
FERTILIZER
APPLICATION
METHOD
Fertilizer P (lb P2O5/acre)
0.2
0.4
0.6
0.8
1.0
Placed or injected 2"
or more deep
Incorporated <1 week
following application
Incorporated > 1 week or
not incorporated following
application in April October
Incorporated >1 week
or not incorporated
following application
in Nov. - March
Surface applied to
frozen or snow
covered soil
Fertilizer Rating = Fertilizer Rate x Fertilizer Application Method
v 2.0
MANURE P
RATE
MANURE
APPLICATION
METHOD
Manure P (lb P2O5/acre)
0.2
0.4
0.6
0.8
1.0
Placed or injected 2"
or more deep
Incorporated <1 week
following application
Incorporated > 1 week or
not incorporated following
application in April October
Incorporated >1 week
or not incorporated
following application
in Nov. - March
Surface applied to
frozen or snow
covered soil
P Source
Coefficient
Refer to: Test results for P Source Coefficient OR Book values from P Index Fact Sheet Table 1
Manure Rating = Manure Rate x Manure Application Method x Manure P Availability
Source Factor Sum
PART B: TRANSPORT FACTORS
EROSION
RUNOFF
0
POTENTIAL
Excessively
SUBSURFACE
0
DRAINAGE
None
Field ID
2
Somewhat Excessively
Soil Loss (ton/A/yr)
4
Well/Moderately Well
1
Random
6
Somewhat Poorly
8
Poorly/Very Poorly
2*
Patterened
6
‡
9
100 to 199 ft. OR
< 100 ft.
<100 ft. with 35 ft. buffer
Transport Sum = Erosion+ Runoff Potential + Subsurface Drainage + Contributing Distance
0.85
1.1
1.0
MODIFIED
50 ft. Riparian Buffer
Direct Connection
Grassed Waterway or
CONNECTIVITY
APPLIES TO DIST
APPLIES TO DIST
None
< 100 FT
> 100 FT
Transport Sum x Modified Connectivity/24
* OR rapid permeability soil near a stream
‡
"9" factor does not apply to fields with a
P Index Value = 2 x Source x Transport
CONTRIBUTING
DISTANCE
35 ft. buffer receiving manure.
0
> 500 ft.
2
350 to 500 ft.
4
200 to 349 ft.
P Index describes P loss potential
Low Medium High
1.2
P loss,
kg/ha
75 kg P/ha TSP
112 kg P/ha swine
slurry
150 kg P/ha
poultry manure
Very high
0.8
0.4
R2=0.79
0
0
50
100
150
200
P index value for the site
Sharpley, USDA-ARS
Phosphorus Index
• Low P Index
– N Based Management
• Medium P Index
– N Based Management
• High P Index*
– P Based: Crop removal
• Very High P Index*
– No P: Manure or Fertilizer
High and Very High*
– Modify Management
based on P
• No or reduced manure
• Change time or method
of application
• Conservation practices
• Buffers
• Etc.
Phosphorus Nutrient Management
Plan
• Develop N based plan
– Usually means excess P will be
applied
• Use P Index to evaluate the N
based plan
Nitrogen Based
Corn/Dairy Manure
N
K2O
or
– Is the risk of P loss acceptable
• Acceptable risk
P2O5
Phosphorus Based
Corn/Dairy Manure
– Apply @ N rate, excess P
• Unacceptable Risk
– Modify N based plan, where
necessary, to address P loss risk
N
P2O5
or
K2O
P Index Application
• Eventually, all fields will have a high P
index
• P Index is not the solution
– Tool to buy time to solve problem
– Minimizes negative impact of P while we come
up with a sustainable solution
– We need to get the system into better balance
NRCS/EPA P Index Issues
• Proposed change in NRCS 590 Std.
– P soil test only – No more P Index
• Easy to regulate
• Very strict limits
• Not supported by the science - Source/Transport
• Unrealistic for animal agriculture to comply with in short
term
• Better soil P balance is a good long term goal
– Withdrawn, under further review
College of Agricultural Sciences
Department of Crop and Soil Sciences