Transcript Colorado Phosphorus Index Risk Assessment

Nutrient enrichment can lead to
excess algae growth
Colorado
Phosphorus Index
Risk Assessment
Version 1.0
November, 2000
Introduction
The Colorado Phosphorus Index (COPI)
Risk Assessment is a tool for planners,
consultants, and producers that may be used
to rank the relative potential for phosphorus
movement to surface water resources from
agricultural fields.
Introduction
The COPI has been developed
cooperatively by the Natural Resources
Conservation Service and Colorado State
University to comply with the Revised
National Nutrient Management Policy
(USDA, April, 1999).
Introduction
A risk assessment is required when manures
or other organic by-products will be land
applied to determine if application rates
should be based on crop nitrogen, or crop
phosphorus requirements.
Objectives
 Terminology
 Site-specific
information requirements
 Preliminary Phosphorus Risk Screening Tool
 COPI Risk Factors
 COPI Risk Interpretations
 Example
Terminology
Contour Buffer Strip - Narrow strips of
permanent, herbaceous vegetative cover
established across the slope and
alternated down the slope with parallel,
wider cropped strips.
Terminology
Cover Crop - Grasses, legumes, or other
herbaceous plants established for seasonal
cover and conservation purposes to: (1)
protect the soil surface from erosion during
periods when it would otherwise be bare;
(2) scavenge excess nutrients from a
previous crop to prevent nutrient loss; or
both.
Terminology
Current Crop Rotation - A planned
sequence of crops growing in a regularly
recurring succession on the same area of
land, as contrasted to continuous culture of
one crop or growing a variable sequence of
crops.
Terminology
Current Soil Test - Current soil tests are
those no older than 5 years.
State or local regulations may require soil
testing at more frequent intervals for some
types of operations.
Terminology
Filter Strip - A strip or area of vegetation
situated between cropland, grazing land, or
disturbed land (including forest land) and
environmentally sensitive areas.
Terminology
Surface Water Resources - Includes water
bodies such as continuous or intermittent
streams, irrigation ditches, drainage ditches,
lakes, and wetlands, etc.
Site-Specific Information
Requirements
 Current
Crop Rotation
 Manure Application History
 Current Soil Test and Extraction Method
 Field Proximity to Surface Water Resources
 Soil Series
 Phosphorus Application Rates
 Phosphorus Application Methods
Preliminary Phosphorus Risk
Screening Tool
A screening tool is included with the index
to make an initial determination as to
whether or not a COPI Risk Assessment
needs to completed for an individual field
and crop rotation.
Preliminary Phosphorus Risk Screening Tool
Will animal manures or other organic
nutrients be applied to this field?
NO 
A Colorado Phosphorus Index Risk
Assessment is not needed for this
field.
YES

Is soil test P greater than:
10 ppm AB-DTPA; 30 ppm Bray P1;
30 ppm Mehlich 3, or; 20 ppm
Olsen (NaCOH3) ?
NO 
A Colorado Phosphorus Index Risk
Assessment is not needed for this
field. Base organic nutrient
application rates on crop nitrogen
requirements.
NO 
A Colorado Phosphorus Index
Risk Assessment is not needed
for this field. Base organic
nutrient application rates on crop
nitrogen requirements.
YES

Can runoff or irrigation tailwater
reach a surface water body?
(continuous or intermittent stream,
irrigation ditch, lake, or wetland,
etc.)
YES

Complete a Colorado Phosphorus
Index Risk Assessment for this
field.
Preliminary Phosphorus Risk
Screening Tool
Question 1
Will manures or other organic nutrients be
applied to this field?
If No, a COPI is not needed for this field.
If Yes, go to Question 2.
Preliminary Phosphorus Risk
Screening Tool
Question 2
Is soil test Phosphorus greater than:
10 ppm AB-DTPA; 30 ppm Bray P1;
30 ppm Mehlich3, or; 20 ppm Olsen
(NaHCO3)?
If No, a COPI is not needed for this field.
If Yes, go to Question 3.
Preliminary Phosphorus Risk
Screening Tool
Question 3
Can field runoff or irrigation tailwater reach
a surface water body? (continuous or
intermittent stream, ditch, lake, or wetland,
etc.)
If No, a COPI is not needed for this field.
If Yes, complete a COPI Risk Assessment.
COPI Risk Factors
 The
COPI is an additive index based on 4
site and management risk factors.
 Each risk factor is rated and assigned a
numeric score of 0, 1, 2, 3, or 4.
 The numeric scores for each factor are then
added together to determine the relative risk
of phosphorus movement off-site.
COPI Risk Factors
1.Runoff Class
Runoff class is based on field slope and the
least permeable soil layer in the top three
feet of the soil profile.
Steep slopes with slow permeability pose a
greater risk than flat slopes with rapid
permeability.
COPI Risk Factors
Table 1. Runoff Class Risk
Soil Permeability Class
Very Rapid
(> 20.0 in/hr)
(>141.14 m/sec)
Rapid and Moderately
Rapid (2.0-20.0 in/hr)
Moderate and
Moderately Slow
(14.11-141.14 m/sec)
(0.2-2.0 in/hr)
(1.41-14.11 m/sec)
Slope %
Depressions
0-1 %
1-5 %
5-10 %
10-20 %
> 20 %
Slow
Very Slow
(0.06-0.2 in/hr)
(0.42-1.41 m/sec)
(< 0.06 in/hr)
(< 0.42 m/sec)
Negligible
Low
Medium
High
High
Very High
Negligible
Low
High
Very High
Very High
Very High
Runoff Class
Negligible
Negligible
Negligible
Very Low
Very Low
Low
Negligible
Negligible
Very Low
Low
Low
Medium
Negligible
Negligible
Low
Medium
Medium
High
COPI Risk Factors
2.Soil Test Phosphorus
Samples for phosphorus soil tests should be
pulled from the top 2 to 3 inches for
continuous no-till cropland, hayland and
pastures, and from the top 8 to 12 inches for
tilled cropland.
COPI Risk Factors
Table 2. Soil Test Phosphorus Risk
Soil Test
Extraction
AB-DTPA
Bray P1
Mehlich 3
Olsen
Low (1)
Medium (2)
High (3)
Very High (4)
< 10 ppm
< 30 ppm
< 30 ppm
< 20 ppm
10-20 ppm
30-60 ppm
30-100 ppm
20-40 ppm
21-40 ppm
61-120 ppm
100-200 ppm
41-80 ppm
> 40 ppm
> 120 ppm
> 200 ppm
> 80 ppm
COPI Risk Factors
3.Phosphorus Application Rate
This is the amount of phosphorus annually
applied, or average annual application rate
calculated for the current crop rotation,
from both organic and inorganic sources.
Organic nutrient content may be estimated
from lab results or book values.
COPI Risk Factors
Table 3a. Phosphorus Application Rate Risk
Phosphorus Application Rate Risk
Rate (lb. P2O5 /ac.)
None (0)
None Applied
Low (1)
< 30
Medium (2)
30-90
High (3)
91-150
Very High (4)
> 150
COPI Risk Factors
Table 3b. Approximate Nutrient Composition of Selected
Types of Manure at Time of Application
Type of Manure
Moisture Content
%
Total N
NH4-N
P2O5
K2O
pounds per ton
Swine
82
10
6
9
8
Beef
32
23
7
24
41
Dairy Cattle
46
13
5
16
34
Sheep
31
29
5
26
38
Chicken w/o litter
55
33
26
48
34
Turkey
w/o litter
78
27
17
20
17
Horse
w/o bedding
22
19
4
14
36
COPI Risk Factors
4.Phosphorus Application Method
The longer phosphorus is exposed on the
soil surface, the greater the risk for
phosphorus loss. Use the highest risk
applicable for multiple phosphorus
applications. Sprinkler applications that do
not exceed soil infiltration capacity are
considered to be a low risk.
COPI Risk Factors
Table 4. Phosphorus Application Method Risk
Application
Method
None (0)
None Applied
Phosphorus Application Method
Low (1)
Medium (2)
High (3)
Injected or
Spring Applied
Fall/Winter Applied
Subsurface
and Incorporated
and Incorporated
Applied
within 2 weeks
within 2 weeks
Very High (4)
Surface Applied with No
Incorporation, or
Fall/Winter Applied with
Spring Incorporation
COPI Risk Factors
5.BMP Implementation Credits
Specific BMPs may be implemented to
decrease the potential for phosphorus loss.
Subtract one point from the gross score for
each of the following BMPs implemented
on-site.
COPI Risk Factors
5.BMP Implementation Credits (cont.)
 Cover or Green Manure crops
 Filter Strips
 Polyacrylamide (PAM)
 Contour Buffer Strips
COPI Risk Interpretations
<8
8 to 11
12 to 15
Low risk
Medium risk
High risk
16
Very high risk
Nitrogen based
Nitrogen based
Phosphorus based
(crop removal)
Phosphorus based
(no application)
Example
 Continuous
minimum till grain corn
 Soil Permeability - Slow
 Slope - 3 to 5 %
 Soil test P - 30 ppm Olsen (NaHCO3)
 Manure - 20 tons applied every 2 years
 App. Method - Fall/winter broadcast/disk
Example
Table 1. Runoff Class Risk
Soil Permeability Class
Very Rapid
(> 20.0 in/hr)
(>141.14 m/sec)
Rapid and Moderately
Rapid (2.0-20.0 in/hr)
Moderate and
Moderately Slow
(14.11-141.14 m/sec)
(0.2-2.0 in/hr)
(1.41-14.11 m/sec)
Slope %
Depressions
0-1 %
1-5 %
5-10 %
10-20 %
> 20 %
Slow
Very Slow
(0.06-0.2 in/hr)
(0.42-1.41 m/sec)
(< 0.06 in/hr)
(< 0.42 m/sec)
Negligible
Low
Medium
High
High
Very High
Negligible
Low
High
Very High
Very High
Very High
Runoff Class
Negligible
Negligible
Negligible
Very Low
Very Low
Low
Negligible
Negligible
Very Low
Low
Low
Medium
Negligible
Negligible
Low
Medium
Medium
High
Example
Table 2. Soil Test Phosphorus Risk
Soil Test
Extraction
AB-DTPA
Bray P1
Mehlich 3
Olsen
Low (1)
Medium (2)
High (3)
Very High (4)
< 10 ppm
< 30 ppm
< 30 ppm
< 20 ppm
10-20 ppm
30-60 ppm
30-100 ppm
20-40 ppm
21-40 ppm
61-120 ppm
100-200 ppm
41-80 ppm
> 40 ppm
> 120 ppm
> 200 ppm
> 80 ppm
Example
Table 3a. Phosphorus Application Rate Risk
Phosphorus Application Rate Risk
Rate (lb. P2O5 /ac.)
None (0)
None Applied
Low (1)
< 30
Medium (2)
30-90
High (3)
91-150
Very High (4)
> 150
Example
Table 4. Phosphorus Application Method Risk
Application
Method
None (0)
None Applied
Phosphorus Application Method
Low (1)
Medium (2)
High (3)
Injected or
Spring Applied
Fall/Winter Applied
Subsurface
and Incorporated
and Incorporated
Applied
within 2 weeks
within 2 weeks
Very High (4)
Surface Applied with No
Incorporation, or
Fall/Winter Applied with
Spring Incorporation
Colorado Phosphorus Index Risk Assessment (Version 1.0)
Factor
None (0)
Low (1)
Medium (2)
High (3)
Very High (4)
Score
Negligible
Very Low or Low
Medium
High
Very High
2
2. Soil Test P
(See Table 2)
Not Applicable
Low
Medium
High
Very High
2
3. P Application
Rate
(Annually applied or
rotational average
lbs. P2O5 per acre
per year, all
sources)
None Applied
< 30
30-90
91-150
> 150
4
Surface Applied
with No
Incorporation, or
Fall/Winter
Applied with
Spring
Incorporation
3
1. Runoff Class
(See Table 1)
None Applied
4. P Application
Method
(Use highest
applicable risk
category for multiple
P applications)
Injected or
Subsurface
Application
Deeper Than 2
inches
Spring Applied
and
Incorporated
within 2 weeks
Fall/Winter
Applied and
Incorporated
within 2 weeks
Gross Score (sum of Factors 1 through 4)
5. BMP
Implementation
Credits
Subtract one point for each of the following BMPs implemented on this site: Cover or
Green Manure Crops; Filter Strips; Polyacrylamides to decrease Irrigation-Induced
Erosion, or; Contour Buffer Strips.
Net Score (sum of Factors 1 through 4 less Factor 5, BMP Implementation Credits)
11
0
11
Score
Phosphorus Index Risk Interpretations
<8
This field has a LOW potential for off-site P movement if management is maintained at the current
level. Organic nutrient application rates may be calculated according to crop nitrogen
requirements.
8 to 11
This field has a MEDIUM potential for off-site P movement and some management changes may
need to be made to support continued long term organic nutrient applications. Organic nutrient
application rates may be calculated according to crop nitrogen requirements.
12 to 15
This field has a HIGH potential for off-site P movement and management changes should be
implemented to decrease risk. Organic nutrient application rates should be calculated according to
crop phosphorus requirements.
16
This field has a VERY HIGH potential for off-site P movement and management changes are
needed to decrease risk. Organic nutrients should not be applied to this field.
Summary
 Terminology
 Site-specific
information requirements
 Preliminary Phosphorus Risk Screening Tool
 COPI Risk Factors
 COPI Risk Interpretations
 Example
For Additional Information...

Jim Sharkoff
[email protected]
(720) 544-2812

Reagan Waskom
(970) 491-6103
[email protected]

Jessica Davis
(970) 491-1913
[email protected]
Finis