Iowa Science Assessment of
Nonpoint Source Practices to
Reduce Phosphorus to the
Mississippi River Basin
Nutrient Reduction Strategy
Phosphorus Science Team
Nutrient Reduction Strategy
Phosphorus Science Team
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Jim Baker – IDALS/ISU
Reid Christianson – ISU
Rick Cruse – ISU
John Kovar – USDA-ARS
Matt Helmers – ISU
Tom Isenhart – ISU
Antonio Mallarino – ISU
Keith Schilling – IDNR
Calvin Wolter – IDNR
Dave Webber - ISU
Approach
1. Establish baseline – existing conditions
– Major Land Resource Areas used to aggregate conditions
2. Extensive literature review to assess potential
performance of practices
– Outside peer review of science team documents (practice
performance and baseline conditions)
3. Estimate potential load reductions of implementing
nutrient reduction practices (scenarios)
– “Full implementation” and “Combined” scenarios
4. Estimate cost of implementation and cost per pound
of nitrogen and phosphorus reduction
Approach
• The P evaluation primarily focused on practices that
limit or control P losses from agricultural land.
• Does not include known sources of P such as point
sources, leaking rural septic systems, and stream
bank erosion.
ISU NREM
USDA NRCS
Approach
• Stream banks are known to be a potentially large source of
suspended and bedded sediments.
• Estimated contributions ranging from 40 to 80% of annual
sediment loads in Midwestern streams.
• Accurate accounting is difficult.
Isenhart et al.
Unpublished
Practice Review Process
• Established an overall list of potential practices
based on input of overall science team
• Shortened the list to those expected to have
greatest potential for nutrient reduction through
detailed discussion of P team – reviewed by
overall science team
• New and emerging practices could be added in
future
Practice Review Process
Phosphorus Reduction Strategies Excluded Due to
Very Limited Impact or Not Information at this Point
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Timing of phosphorus application
Living mulches (e.g. kura clover)
Green manure
No continuous soybean
Shallow drainage
Drainage water management
Bioreactors
Two-stage ditches
Practice Review Process
P reduction practices fall into three main groups
1.
P Management Practices
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2.
Application
Source (commercial fertilizer, manure)
Placement
Cover crops
Tillage
Land use change
• Crop choice
• Perennial vegetation
3.
Erosion Control and Edge of Field Practices
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Terraces
Wetlands
Buffers
Other erosion control
Practice Review Process
• Extensive review of literature from Iowa and
surrounding states
– Used Iowa and surrounding states to try to
have similar soils and climatic conditions
– Reviewed and compiled impacts phosphorus
concentrations and loads
– Reviewed and compiled impacts on corn yield
• Summarized expected practice performance
Nitrogen or Phosphorus?
Nitrogen moves primarily as
nitrate-N with water
Phosphorus moves primarily
with eroded soil
Phosphorus Reduction Practices
• Practices were compared with a corn-soybean
rotation
– P needed by the two crops surface-applied
once after soybean harvest in the fall before
soils freeze
– Tillage includes chisel plowing cornstalks after
harvest and disking/field cultivating in the
spring before planting soybeans
– Before planting corn the normal practice is
disking/field cultivating in the spring
Phosphorus Management Practices
Phosphorus Application Rate
• P rate is less important than N rate as it affects water quality
• P rate affects the STP level, so historical P application rates and current STP level are
important for impacts on water quality
• Application rate is of great concern when any manure type is applied at N-based rates
• Load reduction was estimated using Iowa P Index comparing rates of 200 kg P2O5 ha-1
(max), and 125 kg P2O5 ha-1 (avg.) compared to the average annual removal for a
corn-soybean rotation of 62 kg P2O5 ha-1.
• Estimates in bracket are “worst case scenarios” in which a rainfall occurs within 24
hours of P application
Practice
Phosphorus
Application
Comments
Applying P based on crop removal –
Assuming optimal STP level and P
incorporation
% P Load Reduction
Min
Avg.
(SD)
Max
0
[0]
0.6
[70]
1.3
[83]
Phosphorus Management Practices
Soil Test Phosphorus Level
• Phosphorus loss can be reduced by decreasing total soil P concentration
• This practice assumes limiting or stopping P application to high-testing soils until STP
is lowered to agronomically optimum concentrations of 20 ppm for corn and soybean
production
• Load reduction was estimated using Iowa P Index for a 5 Mg ha-1 erosion rate
• Maximum load reduction was estimated by comparing P loss with an STP of the two
highest counties in IA (125 ppm) to the optimum (20 ppm) STP level
• Average load reduction was estimated based on reducing the average STP of all
counties in IA (40 ppm) to the optimum STP level
• Estimates in brackets are from unpublished work by Mallarino (2011)
Practice
Phosphorus
Application
Comments
Soil-test P – No P applied until STP drops
to optimum
% P Load Reduction
Min
Avg.
(SD)
Max
0
[35]
17
[40]
52
[50]
Phosphorus Management Practices
Site-Specific P Management
• Site-specific management that considers the P loss risk from different areas of a field
could be a beneficial practice to reduce P loss
• Not well studied, but research in IA has found variable-rate fertilizer and manure P
application to be effective in reducing within field variability of STP levels
• The approach used to estimate P load reduction was the same as for the STP practice
and used mean values from a recent unpublished study by Mallarino that included the
mean proportion of IA STP classes for each field
Practice
Comments
% P Load Reduction
Min
Phosphorus
Application
Site-specific P management
0
Avg.
(SD)
Max
14
Phosphorus Management Practices
Source of Phosphorus
• There is little evidence of P source (i.e. fertilizer compared to manure P) effects shortterm delivery from fields if the P is incorporated into the soil
• In the long term, manure can reduce runoff compared to inorganic P forms by
increasing soil organic carbon
• If runoff-producing rainfall events occur immediately after application, less P loss
occurs with solid beef and poultry manure compared with commercial fertilizer
Practice
Source of
Phosphorus
Comments
% P Load Reduction
Min
Avg.
(SD)
Max
Liquid swine, dairy, and poultry manure
compared to commercial fertilizer –
Runoff shortly after application
-64
46
(45)
90
Beef manure compared to commercial
fertilizer – Runoff shortly after application
-133
46
(96)
98
Phosphorus Management Practices
Placement of Phosphorus
• Subsurface banding of P or incorporation of surface-applied P fertilizer or manure on
sloping ground reduces P loss significantly compared with surface application when
runoff-producing precipitation occurs shortly after application
• Estimates in brackets are from a report by Dinnes (2004) and are the author’s best
professional judgment
Practice
Placement of
Phosphorus
Comments
% P Load Reduction
Min
Avg.
(SD)
Max
Broadcast incorporated within 1 week
compared to no incorporation, same
tillage
4
36
(27)
86
With seed or knifed bands compared to
surface application, no incorporation
-50
24
(46)
[35]
95
[-20]
[70]
Phosphorus Management Practices
Cover Crops
• Cover crops reduce erosion by improving soil structure and providing ground cover as
a physical barrier between raindrops and the soil surface
Practice
Cover Crops
Comments
Winter Rye
% P Load Reduction
Min
Avg.
(SD)
Max
-39
29
(37)
68
Phosphorus Management Practices
Tillage
• Tillage practices affect soil erosion, the primary process for P delivery in IA
• Tillage effects on P loss are site specific, but less P loss generally occurs with
minimum or no tillage compared with conventional tillage
• No-till can increase the proportion of total P lost as dissolved P, especially in tiledrained areas
Practice
Tillage
Comments
% P Load Reduction
Min
Avg.
(SD)
Max
Conservation till – chisel compared to
moldboard plowing
-47
33
(49)
100
No-till compared to chisel plowing
27
90
(17)
100
Land Use Change
Crop Choice
• There is very little P loss data for specific extended rotations compared to a cornsoybean rotation in IA
Perennial Vegetation
• Perennial vegetation established as energy crops or land retirement would significantly
reduce soil erosion and P loss
• Delivery of P to water bodies is highly affected by pasture management
Practice
Comments
% P Load Reduction
Min
Crop Choice
Perennial
Vegetation
Extended Rotation
Energy Crops
Max
-13
Land retirement (CRP)
Grazed Pastures
Avg.
(SD)
34
(34)
79
75
2
59
(42)
85
Erosion Control and Edge-of-Field Practices
Buffers
• Designed to reduce P delivery by removing particulate P from runoff through filtration
and sedimentation and reducing dissolved P by plant uptake or soil binding
• Riparian buffers can also stabilize stream banks
Erosion Control
• Designed to reduce sediment delivery
• Includes sedimentation basins, drop structures, ponds, etc.
Practice
Comments
% P Load Reduction
Min
Avg.
(SD)
Max
Terraces
51
77
(19)
98
Buffers
-10
58
(32)
98
75
85
95
Erosion Control
Sedimentation basins or ponds
Phosphorus Reduction Practices
Phosphorus
Management
Practice
% Phosphorus-P Reduction
[Average (Std. Dev.)]
Producer does not apply
phosphorus until STP drops to
optimal level
17 (40)
Source (Liquid swine
compared to commercial)
46 (45)
Incorporation
36 (27)
No-till (70% residue) vs.
conventional tillage (30%
residue)
Perennial – Land retirement
Land Use
Edge-of-Field
90 (17)
75 (-)
Cover Crops (Rye)
29 (37)
Pasture
59 (42)
Buffers
58 (32)
*Load reduction not concentration reduction
P-Index Model
P-Index Inputs for Erosion
Component
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Gross Erosion rate (tons/acre/yr)
Landform Region (Sediment Delivery ratio)
Distance from Stream
Buffer Distance
Enrichment Factor (Tillage/No till)
Soil Test Phosphorus content (ppm P)
Gross Erosion Estimate
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RUSLE model
A = R * K * LS * C * P
A = annual soil loss (tons/yr)
R = rainfall erosivity factor
K = soil erodibility factor
LS = length slope factor
C = cover factor
P = practice factor
County Data from NRCS
Distance Categories to NHD
Stream Network
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0 – 500 ft
500 – 1,000 ft
1,000 – 2,000 ft
2,000 – 4,000 ft
4,000 – 8,000 ft
8,000 – 16,000 ft
> 16,000 ft
Data from SSURGO
• K Factor (soil erodibility factor)
• Slope
• Slope Length
Cover Factor
• Use Crop Rotation information from NASS
CDL
• Use Tillage Practice information from
CTIC
• 7-8 combinations for each MLRA
• Use Section I-C-1 from SCS-Iowa 1990 to
obtain Cover Factor and LS Factor
Practice Factor
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Contour Strip Cropping
Terraces
Contour Strip Cropping and Terraces
Use Section I-C-1 from SCS-Iowa 1990 to
obtain Practice Factor
Gross Erosion Calculation
• A = R * K * LS * C * P
• Perform RUSLE calculation for each
cropping rotation/tillage combination in
each distance class in MLRA
P-Index Model
P-Index Inputs for Runoff
Component
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Landcover condition (crop and residue)
Dominant Soil type
Soil Test Phosphorus content (ppm P)
Fertilizer Application Rate (lb P2O5/acre)
Fertilizer Application Method
Dominant Soil Type in MLRA
Distance Classes
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K Factor
KSat Factor (Saturated Conductivity)
Slope
Slope Length
Find Soil Type that matches all factors the
closest
P-Index Input for Drainage
Component
• Tile Drained soil
• Well Drained soil
Result of P-Index Model
• Phosphorus loss in lbs/ac/year for each
crop rotation/tillage/buffer distance
combination
• Sum up all combinations for MLRA to
obtain total Phosphorus Loss for MLRA
• Perform for each individual management
practice and combinations
Phosphorus Practices –
Potential Load Reduction
Target Load Reduction from NPS
for Hypoxia Goal ~29%
Phosphorus Reduction Scenarios
Scenario: Not applying P on acres with high or very high Soil-Test P (RR)
• This practice involves not applying P on fields where STP values exceed the upper
boundary of the optimum level for corn and soybean in Iowa (20 ppm, Bray-1 or
Mehlich-3 tests, 6-inch sampling depth). This practice would be employed until the
STP level reaches the optimum level.
• Practice limitations, concerns, or considerations
• Limitation to utilization of manure-N. When manure is applied, use of the P Index (which
considers STP together with other source and transport factors) to assess potential impact of
N-based manure on P loss is a reasonable option considering farm economics and other
issues.
• Landlord/tenant contracts often require maintaining STP levels, even if higher than optimum.
Scenario
Phosphorus P rate reduction in MLRAs that
Management have high to very high soil test P
Phosphorus
Potential Area
Reduction
(million acres)
(% from baseline)
7
25.8
Phosphorus Reduction Scenarios
Scenario: Inject/Band P in All No-Till Acres (IN)
• This practice involves injecting liquid P sources (fertilizer or manure) and banding solid
inorganic fertilizers within all current no-till acres.
• Practice limitations, concerns, or considerations
• For inorganic P fertilizers, it adds to the costs and does not increase (nor reduce) yield in Iowa.
• Possible benefits of injecting or banding inorganic P fertilizer containing N by improving N use
efficiency.
• For liquid manure, this is a good practice to use manure-N efficiently.
• For solid manure, there is no practical way to do it yet, but engineering advances for
prototypes being evaluated could make it practical in the future.
Scenario
Phosphorus
Injection/band within no-till acres
Management
Phosphorus
Potential Area
Reduction
(million acres)
(% from baseline)
0.3
4.8
Phosphorus Reduction Scenarios
Scenario: Convert All Intensive Tillage to Conservation Tillage (Tct)
• This practice involves the conversion of all tillage acres to conservation tillage that
covers 30 percent or more of the soil surface with crop residue, after planting, to
reduce soil erosion by water.
• Practice limitations, concerns, or considerations
• No clear data concerning impacts of this type of conservation tillage on possible corn yield
reduction compared with moldboard plowing. However, data suggests the yield reduction is
minimal in most conditions.
• These reduced tillage practices are significantly less efficient than no-till at controlling soil
erosion and surface runoff.
Scenario
Phosphorus Convert all intensive tillage to
Management conservation tillage
Phosphorus
Potential Area
Reduction
(million acres)
(% from baseline)
11
8.6
Phosphorus Reduction Scenarios
Scenario: Convert All Tilled Area to No-Till (Tnt)
• This practice involves the conversion of all tillage to no-till, whereby the soil is left
undisturbed from harvest to planting except for strips up to 1/3 of the row width made
with the planter (strips may involve only residue disturbance or may include soil
disturbance). This practice assumes approximately 70 percent or more of the soil
surface is covered with crop residue, after planting, to reduce soil erosion by water.
• Practice limitations, concerns, or considerations
• No-till results in lower corn yield than with moldboard or chisel-plow tillage. However, the yield
reduction is less or none for other minimum tillage options that, on the other hand, are less
efficient at controlling soil erosion and surface runoff.
• No-till or conservation tillage does not affect soybean yield significantly.
Scenario
Phosphorus
Convert all tillage to no-till
Management
Phosphorus
Potential Area
Reduction
(million acres)
(% from baseline)
39
16.1
Phosphorus Reduction Scenarios
Scenarios: Plant a rye cover crop on all corn-soybean and continuous corn acres
(CCa)
Plant a rye cover crop on all no-till acres (CCnt)
• The cover crop in this practice/scenario is late summer or early fall seeded winter
cereal rye.
• Practice limitations, concerns, or considerations
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Impact on seed industry due to increased demand for rye seed.
Row crops out of production to meet rye seed demand.
New markets for cover crop seed production and establishment.
Livestock grazing.
Corn and soybean planting equipment designed to manage cover crops in no-till.
Negative impact on corn grain yield for species with spring growth.
Scenario
Phosphorus Cover crops (rye) on all CS and
Management CC acres
Cover crops on all no-till acres
Phosphorus
Reduction
(% from
baseline)
Potential Area
(million acres)
50
21.0
4
4.8
Phosphorus Reduction Scenarios
Scenario: Establishing 35 foot buffers on all crop land (BF)
• Buffers have the potential to be implemented adjacent to streams to intercept overland
flow and reduce P transport to receiving waters.
Scenario
Edge-of-Field
Establish streamside buffers (35
ft.) on all crop land
Phosphorus
Potential Area
Reduction
(million acres)
(% from baseline)
18
0.4
Phosphorus Reduction Scenarios
Scenario: Perennial Crops (Energy Crops) Replacing Row Crops (EC)
• This scenario switches corn and soybean row crop land to energy crops at the amount
equivalent to reach the total number of acres in pasture/hay in 1987 for each MLRA.
Row crop acres were reduced proportionally for the corn-soybean rotation and
continuous corn.
• Practice limitations, concerns, or considerations
• Immediate limited market for perennials as energy crops.
• Market shifts in crop prices and demand.
Scenario
Land Use
Change
Perennial crops (Energy crops)
equal to pasture/hay acreage from
1987. Take acres proportionally
from all row crop. This is in
addition to current pasture.
Phosphorus
Potential Area
Reduction
(million acres)
(% from baseline)
29
5.9
Phosphorus Reduction Scenarios
Scenario: Grazed Pasture and Land Retirement Replacing Row Crops (P/LR)
• This scenario increases the acreage of pasture and retired land to equal the
pasture/hay and retired land acreage in 1987, which was the first time land was
enrolled in the Conservation Reserve Program (CRP). Row crop acres were reduced
proportionally for corn-soybean rotation and continuous corn.
• Practice limitations, concerns, or considerations
• Market and price shifts due to reduced row crop production.
• New markets for grass-fed beef.
Land Use
Change
Scenario
Phosphorus
Reduction
(% from
baseline)
Potential Area
(million acres)
Pasture and Land Retirement to
equal acreage of Pasture/Hay and
CRP from 1987 (in MLRAs where
1987 was higher than now). Take
acres from row crops
proportionally.
9
1.8
Phosphorus Reduction Scenarios
Scenario: Extended Rotation (corn-soybean-alfalfa-alfalfa-alfalfa) (EXT)
• This scenario Increases the acreage of extended rotations by doubling the current
amount of extended rotations (and reducing proportionally the corn-soybean rotation
and continuous corn) in each MLRA.
• Practice limitations, concerns, or considerations
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Reduce the amount of corn and soybean produced in Iowa.
Market shift in product production (more alfalfa) and associated price for crops produced.
Increased livestock production to feed alfalfa.
Market shift as little fertilizer N is needed for corn following alfalfa.
Scenario
Land Use
Change
Doubling the amount of extended
rotation acreage (removing from
CS and CC proportionally)
Phosphorus
Reduction
(% from
baseline)
Potential Area
(million acres)
3
1.8
Phosphorus Reduction Scenarios
Scenario
Phosphorus
Potential Area
Reduction
(million acres)
(% from baseline)
Cover crops (rye) on all CS and
CC acres
50
21.0
Convert all tillage to no-till
39
16.1
Convert all intensive tillage to
conservation tillage
11
8.6
4
4.8
7
25.8
0.3
4.8
Phosphorus Cover crop (rye) on all no-till acres
Management
Phosphorus rate reduction in
those MLRAs that have high to
very high soil test phosphorus
Injection within no-till acres
Target Load Reduction from NPS for Hypoxia Goal ~29%
Phosphorus Reduction Scenarios
Scenario
Edge of
Field
Phosphorus
Potential Area
Reduction
(million acres)
(% from
baseline)
Buffers (35 feet) on all crop land
18
0.4
Perennial crops (Energy crops) equal to
pasture/hay acreage from 1987. Take acres
proportionally from all row crop. This is in
addition to current pasture.
29
5.9
Pasture and land retirement to equal
Land Use pasture/hay, and CRP acreage from 1987
Change (in MLRAs where 1987 was higher than
now). Take acres from row crops
proportionally.
9
1.9
Doubling the amount of extended rotation
acreage (removing from CS and CC
proportionally).
3
1.8
Target Load Reduction from NPS for Hypoxia Goal ~29%
Combined Phosphorus Reduction Scenarios
Examples!
Combination Scenarios
P
Reduction
Nitrate-N
Reduction
(% from (% from
baseline) baseline)
Scenario
Practice/Scenario
PCS1
Phosphorus rate reduction on all ag acres (CS,CC,EXT, and pasture)/Conservation
tillage on all CS and CC acres/Buffers on all CS and CC acres
30
7
PCS2
Phosphorus rate reduction on 56% of all ag acres (CS,CC,EXT, and
pasture)/Convert 56% of tilled CS and CC acres to No-Till/Buffers on 56% CS and
CC acres
29
4
PCS3
Phosphorus rate reduction on 53% of all ag acres (CS,CC,EXT, and
pasture)/Convert 53% of tilled CS and CC acres to No-Till/Cover crops on No-till
CS and CC acres
29
14
PCS4
Phosphorus rate reduction on 63% of ag acres (CS,CC,EXT, and pasture)/Convert
63% of tilled CS & CC acres to No-till and cover crops on No-till crop acres except
for MLRAs 103 and 104
29
9
PCS5
Phosphorus rate reduction on 48% of ag acres (CS,CC,EXT, and pasture)/Convert
48% of tilled CS and CC acres to No-till with Cover Crop on No-till acres /Buffers
on 48% CS and CC acres
29
16
Combined Nitrogen and Phosphorus
Reduction Scenarios
Examples!
Nitrate-N
Practice/Scenario
Phosphorus
% Reduction from baseline
NCS1
Combined Scenario (MRTN Rate, 60% Acreage with
Cover Crop, 27% of ag land treated with wetland
and 60% of drained land has bioreactor)
42
30
NCS3
Combined Scenario (MRTN Rate, 95% of acreage in
all MLRAs with Cover Crops, 34% of ag land in
MLRA 103 and 104 treated with wetland, and 5%
land retirement in all MLRAs)
42
50
NCS8
Combined Scenario (MRTN Rate, Inhibitor with all
Fall Commercial N, Sidedress All Spring N, 70% of
all tile drained acres treated with bioreactor, 70%
of all applicable land has controlled drainage,
31.5% of ag land treated with a wetland, and 70%
of all agricultural streams have a buffer) Phosphorus reduction practices (phosphorus rate
reduction on all ag land, Convert 90% of
Conventional Tillage CS & CC acres to Conservation
Till and Convert 10% of Non-No-till CS & CC ground
to No-Till)
42
29
Future Needs
Phosphorus management
• Impacts on water quality of variable-rate fertilizer and
manure P application technology
• Development of commercially viable inorganic P
fertilizer materials without N, so N and P
management can be handled separately if needed
• Field research based on large plots or catchments to
study the impacts on P loss of alternative P
management practices
• Validation of the Iowa P index as an edge-of-field and
watershed scale assessment tool
Future Needs
In-field and edge-of-field soil and water conservation practices
• An efficient method to estimate ephemeral gully erosion and
delivery of sediment
• Water quality data comparing extended rotations, pastures,
and land retirement to a corn-soybean rotation
• Cover crop management techniques adapted to Iowa to limit
the risk to corn yield reduction including development of new
cover crop species and varieties
• Direct measurement of P loss from field edge and to surface
water systems
• Development and evaluation of management practices to
reduce stream bank erosion and sediment delivery
Notes
• Phosphorus assessment does not include stream
bed and bank contribution
• It appears that nutrient strategy reduction goals
for P would be achieved under most scenarios
meeting the goal for N
• If considered independently from N, P goals
could be achieved at lower total cost with
practices implemented on an MLRA basis
Summary
• Process has identified practices that have greatest potential
for nutrient load reduction
• Process has estimated potential field-level costs associated
with practice implementation and is also considering largerscale economic impacts of practice implementation
• To achieve goals will require a combination of practices
• N versus P requires different practices
• Multiple benefits of practices will need to be considered
• Knowing the starting point is still a challenge and knowing
what is being done on the land could (would) improve
estimates of progress that can be made
Combined Phosphorus Reduction Scenarios
Scenario PCS1
1. Phosphorus is not applied to all agricultural acres (CS, CC, EXT, and pasture) where STP values exceed the optimum level
(20 ppm). This practice would be used until the STP level reaches the optimum level.
2. Conservation tillage is used on all CS and CC acres
3. Streamside buffers are established on CS and CC acres.
Scenario PCS2
1. Phosphorus is not applied to 56% of agricultural acres (CS, CC, EXT, and pasture) where STP values exceed the optimum
level (20 ppm). This practice would be used until the STP level reaches the optimum level.
2. No-till is used on 56% of tilled CS and CC acres.
3. Streamside buffers are established on 56% of CS and CC acres.
Scenario PCS3
1. Phosphorus is not applied to 53% of agricultural acres (CS, CC, EXT, and pasture) where STP values exceed the optimum
level (20 ppm). This practice would be used until the STP level reaches the optimum level.
2. No-till is used on 53% of tilled CS and CC acres.
3. Cover crops are used on all no-till CS and CC acres.
Scenario PCS4
1. Phosphorus is not applied to 63% of agricultural acres (CS, CC, EXT, and pasture) where STP values exceed the optimum
level (20 ppm). This practice would be used until the STP level reaches the optimum level.
2. No-till is used on 63% of tilled CS and CC acres and cover crops established on no-till acres, except for MLRA 103 and 104.
Scenario PCS5
1. Phosphorus is not applied to 48% of agricultural acres (CS, CC, EXT, and pasture) where STP values exceed the optimum
level (20 ppm). This practice would be used until the STP level reaches the optimum level.
2. No-till is used on 48% of tilled CS and CC acres and cover crops established on no-till acres.
3. Streamside buffers are established on 48% of CS and CC acres