**TECHNICAL NOTES**

**USDA-Natural Resources Conservation Service**

**Boise, Idaho**

##### ***TN - Water Quality No[.]{.smallcaps} 6 August 2006***

IDAHO NUTRIENT TRANSPORT RISK ASSESSMENT (INTRA)

A Water Quality Risk Assessment Tool for Conservation Planning

# The Idaho Nutrient Transport Risk Assessment (INTRA) uses a limited number of landform, site and management characteristics to determine the probability of off-site transport of nutrients (primarily nitrogen and phosphorus). The purpose of the Risk Assessment is to provide planners with a tool to evaluate the various landforms and management practices for potential risk of nutrient movement to surface and ground water. The assessment tool is used [during the planning process]{.underline} to determine if surface and/or ground water quality concerns exist. The tool is similar to the risk assessment within OnePlan, but is modified to use with conservation management units, not individual fields. The tool was field-tested in both northern and southern Idaho in a number of different landuse-operation scenarios. The tool provides recommendations to assist the planner in selecting appropriate conservation practices that address individual and multiple risk factors to protect or enhance water quality. These mitigating practices are required in order to meet quality criteria for nutrients and organics in surface and ground water if the final risk level is greater than LOW. A brief summary of nutrient movement in agricultural systems, primarily phosphorus and nitrogen, follows. For a more detailed description, refer to *Idaho Water Quality Technical Note Nos. 4 and 5*.

## 

## Summary of Nutrient Movement in Agricultural Systems

# 

# [Phosphorus]{.underline}

# Phosphorus movement in runoff occurs as particulate P and dissolved P. Particulate P is attached to mineral and organic sediment as it moves with the runoff. Dissolved P is in the water solution. In general, particulate P is the major portion (75%-90%) of the P transported in runoff from cultivated land. Dissolved P makes up a larger portion of the total P in runoff from non-cultivated lands such as pastures and fields with reduced tillage. 

#  

# As runoff moves from the landscape towards surface water, phosphorus may become more bioavailable by the sorption and desorption processes, and by the preferential transport of clay-sized material as sediment moves over the landscape (enrichment). The interaction between the particulate and dissolved P in the runoff is very dynamic and the mechanism of transport is complex. Additionally, dissolved P can move laterally towards surface water bodies as subsurface flow, or downwards, as the soil reaches P saturation. Therefore, it is difficult to predict the transformation and ultimate fate of P as it moves through the landscape (Sharpley et al. 2003).

## Nitrogen

Nitrogen is one of the most dynamic and mobile nutrients in the
plant-soil-air continuum with many pathways for loss. There is a large
reservoir of N in soil, but most of this is in the organic form. It is
estimated that only 2%-3% of organic N is mineralized annually. The
mineralized form of N (nitrate and ammonium) is readily available for
uptake by plants. The N cycle is both spatially and temporally variable
within agricultural systems. Variability of soil properties impacts
nitrogen movement and loss within agricultural operations, including
soil organic matter, residual nitrate, crop residue amount, crop yield
variability and changes in soil chemical and physical properties across
the field. The primary loss mechanism of nitrogen in agricultural
systems is leaching of nitrate below the root zone. However, losses of
nitrogen to the air and by overland flow also occur.

Management plays a critical role in reducing N loss to the environment,
and management is [the]{.underline} dominant factor influencing
long-term nitrate leaching (Shaffer and Delgado 2002). Soil, climate,
watershed and aquifer characteristics must also be taken into account in
order to minimize nitrate leaching. Loss of nitrate from agricultural
systems can range from 0% - 60% of N applied (Meisinger and Delgado
2002). Leaching loss is dependent on the concentration of N in soil
solution and the volume of water leached. Over-irrigation can lead to
nitrate leaching, especially with shallow rooted crops. Effective
management is therefore aimed at reducing transport through proper
irrigation water management, and optimizing N application amounts and
timing in concert with crop uptake. Crop type and cultivation are also
important considerations.

## 

## The Idaho Nutrient Transport Risk Assessment: Risk Factors

# The main factors influencing nutrient movement in agricultural systems can be separated into transport, source and management factors. Transport factors include the mechanisms by which nutrients move within the landscape. These are rainfall, irrigation, erosion and runoff and deep percolation. Factors which influence the source and amount of nutrients available for transport include soil nutrient content and form of nutrient applied. Management factors include the method of application, timing and placement in the landscape as influenced by the management of application equipment and tillage.

# 

# When the factors of the assessment are analyzed, it will be apparent when an individual factor (or factors) is influencing the assessment disproportionately. These identified factors are the basis for planning corrective soil and water conservation practices and management techniques. 

# 

# The soil, hydrology, climate and land management site characteristics that have a major influence on nutrient availability, retention, management and movement are listed below. The number in parentheses after each factor is the relative weighting factor.

# 

# Soil test P (available phosphorus in soil laboratory test units relative to the 0-12" soil layer *Phosphorus Threshold* per Idaho Nutrient Management Practice Standard 590) (1.0)

# P fertilizer application rates (in pounds available phosphate per acre) (0.75)

# P fertilizer application methods (0.5)

# Organic P source application rates (in pounds available phosphates per acre) (1.0)

# Organic P source application methods (0.75) 

-   N fertilizer application rate (1.0)

-   N application timing (1.00 if non-irrigated, 0.75 if irrigated)

# N fertilizer application method (0.75)

# Irrigation runoff index (0.5)

# Runoff class (0.5)

# Runoff conservation practices (-1.0)

# Sheet and rill and/or irrigation-induced soil erosion (in tons per acre per year) (1.0)

-   Distance to the nearest receiving water body (1.0)

-   Irrigation index (for deep percolation) (1.5)

-   Leaching index (0.5 irrigated, 1.5 non-irrigated)

-   Water table depth, geologic features and hydrologic group (1.00 if
    irrigated, 1.5 if non-irrigated)

# Field-specific data for the site characteristics selected for this version of the Risk Assessment (Table 1) are readily available at the conservation management unit level. Some analytical testing of the soil and organic material is required to determine the rating levels. This soil and organic material analysis is considered essential as a basis for the assessment.

# 

The factors (described below) used in the assessment are rated as VERY
LOW, LOW, MEDIUM, HIGH or VERY HIGH (and some use CRITICAL) by
determining the range for each category. The sum of the site
characteristic rankings provides an index for surface water quality
(Table 2) and an index for ground water quality (Table 3).

## Soil P Test

A soil sample (0-12") from the site is necessary to assess the relative
level of \"plant available P\" in the surface layer of the soil. The
plant available P is the level customarily given in a soil test analysis
by the Cooperative Extension Service or commercial soil test
laboratories. The Assessment uses ranges of soil test P. The Olsen
(bicarbonate), Bray I or Morgan (sodium acetate) soil test P methods are
required by the Natural Resources Conservation Service (NRCS) Idaho
Nutrient Management Standard depending upon the soil pH. The soil test
level for \"plant available P\" does not ascertain the total P in the
surface soil. Rather, it gives an indication of the relative amount of
total P that may be present due to the general relationship between the
forms of P (organic, adsorbed and labile P) and the solution P available
for plant uptake. If a soil test P result is above the phosphorus
threshold as identified in the Idaho Nutrient Management Standard (590),
the rating automatically defaults to CRITICAL.

## P Fertilizer Application Rate

The P fertilizer application rate is the amount, in pounds per acre
(lbs/ac), of commercial phosphate fertilizer (P~2~0~5~) applied to the
soil. This phosphate fertilizer does not include phosphorus from organic
sources that are recorded in Organic P Sources Application Rate.

## P Fertilizer Application Method

The manner in which P fertilizer is applied to the soil affects
potential P movement. Incorporation implies that the fertilizer P is
buried below the soil surface. If fertilizer is surface applied on a
field with surface runoff (natural or from irrigation) and there is no
incorporation, it is considered a significant risk and therefore the
rating automatically defaults to CRITICAL.

## Organic P Source Application Rate

The organic P application rate is the amount, in pounds per acre
(lbs/ac), of potential phosphate (P~2~0~5~) contained in the manure and
applied to the soil. This organic phosphate source does not include
phosphorus from fertilizer sources that are recorded in P Fertilizer
Application Rate.

## Organic P Source Application Method

The manner in which organic P material is applied to the soil can
determine potential P movement. Incorporation implies that the organic P
material is buried below the soil surface. If manure is surface applied
on a field with surface runoff (natural or from irrigation) and there is
no incorporation, it is considered to be a discharge and a violation of
existing regulations. Because of this, the rating automatically defaults
to CRITICAL.

## Runoff Class and Irrigation Runoff Index

***Runoff Class:*** The runoff class of the site is used to determine
the risk of runoff from storm events. One method to determine the runoff
class is based on the soil permeability and the percent slope of the
site (USDA-NRCS Soil Survey Manual, Agricultural Handbook 18, 1993). The
matrix relating soil permeability class and slope (Table 4) provides the
appropriate value category. This information is available in the SSURGO
soils database (physical properties report).

***Runoff Index:*** The irrigation runoff index of the site is used for
irrigated lands. For sprinkler irrigated lands, the runoff index is
simply based on a user supplied assessment of whether or not runoff
(overland flow) exists and, if so, whether or not it leaves the field.
For surface irrigated lands, the runoff index is based on the typical
percent of the irrigation set time that runoff from the furrow/field
occurs; the user enters whether it is more or less than 50%.

## 

## Runoff Conservation Practices

Runoff conservation practices include any conservation practices which
serve to reduce runoff and the movement of soil, thereby reducing
potential for dissolved and particulate phosphorus movement across the
landscape toward a receiving water body. Credit (negative point value)
is applied depending on the number of conservation practices
implemented, so multiple practices receive greater credit than a single
practice. Also, runoff conservation practices that filter or trap
nutrients (such as buffers, borders, filter strips and grassed
waterways) receive greater credit than those that simply reduce runoff.
Certain practices (e.g., tail-water recovery systems with sediment
basins) eliminate runoff and sediment loss from the field.

## Soil Erosion (Total Water-Induced Soil Erosion)

Soil erosion is defined as the loss of soil along the slope or
unsheltered distance caused by the processes of water and wind. Soil
erosion is estimated from erosion prediction models including the
Revised Universal Soil Loss Equation (RUSLE/RUSLE2) for water erosion
from non-irrigated lands (and sprinkler irrigated lands if runoff
exists) and the Surface Irrigation Soil Loss equation (SISL) for water
erosion from surface irrigated lands. The Wind Erosion Equation (WEQ) is
[not]{.underline} used in this assessment. The value category is given
in tons of soil loss per acre per year (ton/ac/yr). These soil loss
prediction models [do not]{.underline} predict sediment delivery rates
from the end of a field to a water body. The prediction models are used
in this assessment to indicate the [potential]{.underline} for sediment
and attached nutrient movement across the slope or unsheltered distance
toward surface waters.

**Distance to Nearest Receiving Water Body**

The distance to the nearest receiving water body is the distance in feet
between the edge of the field and the nearest receiving water. This is
typically a ditch, canal, waterway, drain, etc. -- *any water body or
water way which has connection (perennial or ephemeral) with a stream,
river, pond or lake*. The closer the distance, the greater the
likelihood nutrients lost from the field will reach the receiving water
body.

## Leaching Index

Deep percolation is dependent on numerous factors including climate and
soil type. The leaching index is based on the Nitrogen Leaching Index
(Czymmek et al. 2003, Williams and Kissel 1991) which is essentially a
water percolation index based on soil water storage. Slight
modifications were made to some of the percolation index equations to
adjust for low precipitation zones found in areas of Idaho. Total annual
precipitation for specific locations is determined from local climate
station data, as is winter precipitation. The percolation index is based
on precipitation and hydrologic soil groups. A seasonal index is
calculated as the ratio of winter precipitation to annual precipitation.
The leaching index is then calculated as the product of the percolation
index and seasonal index. For irrigated lands, the leaching index is low
if the irrigation index is low. If not, then the leaching index is based
on the amount of winter precipitation.

## Irrigation Index

Managing irrigation water will minimize nutrient losses from leaching
and surface runoff. Potential system application efficiency and
irrigation water management have significant impacts on actual water
movement through the root zone. Five different factors are used in the
irrigation index to determine the potential for irrigation water to
transport nutrients to ground water. The irrigation system is the
primary rating factor, and the other variables modify that rating based
on the level of management for each. These additional factors are water
control and measurement, irrigation scheduling and soil moisture
monitoring, use of pre- and/or post-season irrigation and soil condition
index (SCI).

## N Application Index

Crop nitrogen requirement is determined based on crop yield and
University of Idaho fertilizer recommendations. The nitrogen application
rate is the percent nitrogen applied compared to the total crop nitrogen
requirement according to the fertilizer guides [prior to]{.underline}
any credits or debits for previous crop and residual nitrogen.

## N Application Timing

Timing of N application directly influences potential transport due to
the high mobility of nitrate in soils. The appropriate timing of N
application is complicated by the soil processes of nitrification,
volitization and mobilization which affect N plant availability. Split
applications of N throughout the growing season better match crop growth
requirements, reducing the likelihood of loss. Fall application, in most
instances, has the greatest potential for loss prior to the planting
season; additional N applications are often required to meet crop demand
when losses occur.

## Water Table Depth/Soil Type

Soils can stop or slow nutrient movement depending on their chemical and
physical characteristics. Depth of soils, depth to water tables and
limiting layers such as hard pans will influence rooting depth, nitrogen
movement and leaching potential. Fine textured soils (Hydrologic Group
D) have a lower potential for leaching due to reduced permeability and
high water holding capacity, while coarse textured soils (Hydrologic
Group A) have a higher likelihood of nitrate leaching due to low water
holding capacity and the rapid infiltration and movement of water
through the profile.

If a water table is present within five feet of the surface, the
potential for ground water contamination is high regardless of the soil
type.

## Using the Idaho Nutrient Transport Risk Assessment 

The Assessment applies on cropland, hayland and pasture where nutrients
are applied. Use of the Risk Assessment for planning should begin
[during]{.underline} the initial field visit and interview with the
producer. However, some of the information needed for the factors will
be obtained from other planning tools (for instance, SISL or RUSLE2,
soils database, etc.). **A field data sheet is provided in the
spreadsheet, but required calculations and look-up information is
performed by the spreadsheet, so entering information from the field
data sheet into the spreadsheet (or taking the computer to the field)
[is required]{.underline}**. Steps for using the assessment tool are:

1)  An assessment is developed for each land use, conservation
    management unit or cropping system.

> Example: An operation includes 3 cropping systems or conservation
> management units:

1.  Hay in rotation with row crops and cereals, where commercial
    fertilizer is applied.

2.  Hay in rotation with row crops and cereals where animal waste is
    applied in addition to commercial fertilizer.

3.  Pasture where commercial fertilizer is applied.

> An assessment is required for each system/management unit.

2)  Identify the critical crop in each system. The critical crop is the
    crop in which the highest potential for off-site transport of
    nutrients exists. For example, a rotation being evaluated includes
    winter wheat, spring barley and summer fallow. All the nitrogen for
    winter wheat is applied in the fall prior to planting the crop. The
    critical crop is winter wheat. The assessment is made using
    information which relates to the winter wheat crop.

3)  The planner must obtain the following information from the producer.

    1.  Typical rotation.

    2.  For the critical crop:

        a.  Soil test data using the appropriate analysis method (Olson,
            Bray or Sodium Acetate). **Note:** If no soil test has been
            done in the last 5 years, the input value is automatically a
            VERY HIGH.

        b.  Phosphorus fertilizer application rate (lbs/ac/yr).

        c.  Phosphorus fertilizer application method.

        d.  Organic phosphorus application rate (lbs/ac/yr). **Note:**
            If the producer can not provide this information, the input
            value is automatically a VERY HIGH.

        e.  Organic phosphorus fertilizer application method.

        f.  Nitrogen application rate (% of Crop Requirement) requires 2
            factors. The actual lbs/ac/yr of Nitrogen applied and the
            target yield. The program uses these 2 values to generate
            the rating.

        g.  Nitrogen fertilizer application method.

        h.  Runoff Index (Surface Irrigated). This value is qualitative.
            The planner determines the input by asking the producer
            whether water runs off less than or more than 50% of the set
            time.

        i.  Runoff Index (Sprinkler Irrigated). This value is
            qualitative. The planner determines the input with on-site
            observation and/or asking the producer. Does water move
            across the field surface during irrigation? Does water leave
            the field via overland flow?

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4)  Other Information: Factors like hydrologic soil group, average field
    slope, permeability, soil erosion and distance to surface waters are
    required and should be representative of the cropping
    scenario/conservation management unit being evaluated.

**Requirements for Meeting Quality Criteria**

-   Quality Criteria is met when an overall rating of LOW is obtained.
    No mitigating practices are required.

-   Quality Criteria is not met when an overall rating of MEDIUM or
    greater is obtained. Mitigating practices are required. If
    [all]{.underline} possible mitigating practices have already been
    implemented, then Quality Criteria are considered met. [This must be
    documented in the plan.]{.underline}

**Identification of Mitigating Practices**

The rating for each site characteristic (factor) is displayed on the
Assessment Report. If any site characteristic has a MEDIUM or higher
rating, then mitigating practices are required. Mitigating practices are
not required for any site characteristic which has a rating of LOW;
however, "Recommended" practices might be suggested. "Recommended" and
"Required" practices are identified on the report in the column titled
"Mitigating Practices".

## References

Czymmek, KJ, QM Ketterings, HM van Es, and SD DeGloria. 2003. The New
York Nitrate Leaching Index. Cornell University, Department of Crop and
Soil Sciences, Extension Publication E03-2.

Meisinger, JJ, and JA Delgado. 2002. Principles of managing nitrogen
leaching. J. Soil and Water Conservation 57: 485 - 498.

Shaffer, MJ, and JA Delgado. 2002. Essentials of a national nitrate
leaching index assessment tool. J. Soil and Water Conservation 57: 327
-- 335.

Sharpley, AN, T Daniel, T Sims, J Lemunyon, R Stevens, and R Parry.
2003. Agricultural phosphorus and eutrophication (second edition).
USDA-Agricultural Research Service, ARS-149.

USDA-NRCS Conservation Practice Standard, Nutrient Management, Idaho
590.

USDA-NRCS, Engineering Technical Note, Series 1901. A Phosphorus
Assessment Tool, August 1994.

USDA-NRCS Soil Survey Manual, Agricultural Handbook 18, 1993.

Williams, JR, and DE Kissel. 1991. Water percolation: an indicator of
nitrogen-leaching potential. pp 59-83 *[IN]{.underline}*: RF Follet, DR
Keeney, and RM Cruse (eds). Managing nitrogen for groundwater quality
and farm profitability. Soil Science Society of America, Inc. Madison,
WI

**Table 1. Idaho Nutrient Transport Risk Assessment for Planning (Field
Sheet). The weighting for each factor is incorporated into the point
value.**

+----------+-------+-------+--------+-------+--------+--------+------+
| *        |       |       |        |       |        |        |      |
| *Surface |       |       |        |       |        |        |      |
| Water    |       |       |        |       |        |        |      |
| Q        |       |       |        |       |        |        |      |
| uality** |       |       |        |       |        |        |      |
+----------+-------+-------+--------+-------+--------+--------+------+
| **Site   | **R   |       |        |       |        |        | **   |
| Characte | ating |       |        |       |        |        | SELE |
| ristic** | and   |       |        |       |        |        | CTED |
|          | Point |       |        |       |        |        | RATI |
|          | Va    |       |        |       |        |        | NG** |
|          | lue** |       |        |       |        |        |      |
+----------+-------+-------+--------+-------+--------+--------+------+
|          | Very  | Low   | Medium | High  | Very   | Cr     |      |
|          | Low   |       |        |       | High   | itical |      |
|          |       | 1     | 2      | 4     |        |        |      |
|          | 0     |       |        |       | 8      | 10     |      |
+----------+-------+-------+--------+-------+--------+--------+------+
| **Soil   | \< 8  | 8 -   | 16 -   | 26 -  | 36 --  | \> 40  |      |
| Test P   |       | 15    | 25     | 35    | 40     |        |      |
| (ppm)**  |       |       |        |       |        |        |      |
|          |       |       |        |       | (or no |        |      |
| **Olsen  |       |       |        |       | soil   |        |      |
| Method** |       |       |        |       | test)  |        |      |
|          |       |       |        |       |        |        |      |
| **0 --   |       |       |        |       |        |        |      |
| 12"**    |       |       |        |       |        |        |      |
+----------+-------+-------+--------+-------+--------+--------+------+
| **Soil   | \< 10 | 10 -  | 21 -   | 41 -  | 51- 60 | \> 60  |      |
| Test P   |       | 20    | 40     | 50    |        |        |      |
| (ppm)**  |       |       |        |       | (or no |        |      |
|          |       |       |        |       | soil   |        |      |
| **Bray   |       |       |        |       | test)  |        |      |
| Method** |       |       |        |       |        |        |      |
|          |       |       |        |       |        |        |      |
| **0 --   |       |       |        |       |        |        |      |
| 12"**    |       |       |        |       |        |        |      |
+----------+-------+-------+--------+-------+--------+--------+------+
| **Soil   | \<    | 1.0   | 2.1 -- | 4.1   | 5.1-   | \> 6.0 |      |
| Test P   | 1.0   | --    | 4.0    | --    | 6.0    |        |      |
| (ppm)**  |       | 2.0   |        | 5.0   |        |        |      |
|          |       |       |        |       | (or no |        |      |
| **Morgan |       |       |        |       | soil   |        |      |
| Method   |       |       |        |       | test)  |        |      |
| (        |       |       |        |       |        |        |      |
| NaOAc)** |       |       |        |       |        |        |      |
|          |       |       |        |       |        |        |      |
| **0 --   |       |       |        |       |        |        |      |
| 12"**    |       |       |        |       |        |        |      |
+----------+-------+-------+--------+-------+--------+--------+------+
| **Site   | **R   |       |        |       |        |        | **   |
| Characte | ating |       |        |       |        |        | SELE |
| ristic** | and   |       |        |       |        |        | CTED |
|          | Point |       |        |       |        |        | RATI |
|          | Va    |       |        |       |        |        | NG** |
|          | lue** |       |        |       |        |        |      |
+----------+-------+-------+--------+-------+--------+--------+------+
|          | Very  | Low   | Medium | High  | Very   | Cr     |      |
|          | Low   |       |        |       | High   | itical |      |
|          |       | 0.75  | 1.5    | 3     |        |        |      |
|          | 0     |       |        |       | 6      |        |      |
+----------+-------+-------+--------+-------+--------+--------+------+
| **Ph     | 0     | \< 60 | 60 -   | 151-  | \> 300 |        |      |
| osphorus |       |       | 150    | 300   |        |        |      |
| Fe       |       |       |        |       |        |        |      |
| rtilizer |       |       |        |       |        |        |      |
| App      |       |       |        |       |        |        |      |
| lication |       |       |        |       |        |        |      |
| Rate     |       |       |        |       |        |        |      |
| (lbs/ac  |       |       |        |       |        |        |      |
| P~2      |       |       |        |       |        |        |      |
| ~O~5~)** |       |       |        |       |        |        |      |
+----------+-------+-------+--------+-------+--------+--------+------+
| **Site   | **R   |       |        |       |        |        | **   |
| Characte | ating |       |        |       |        |        | SELE |
| ristic** | and   |       |        |       |        |        | CTED |
|          | Point |       |        |       |        |        | RATI |
|          | Va    |       |        |       |        |        | NG** |
|          | lue** |       |        |       |        |        |      |
+----------+-------+-------+--------+-------+--------+--------+------+
|          | Very  | Low   | Medium | High  | Very   | Cr     |      |
|          | Low   |       |        |       | High   | itical |      |
|          |       | 0.5   | 1.0    | 2     |        |        |      |
|          | 0     |       |        |       | 4      | 10     |      |
+----------+-------+-------+--------+-------+--------+--------+------+
| **Ph     | None  | P     | Incorp | Chemi | S      | S      |      |
| osphorus | ap    | laced | orated | gated | urface | urface |      |
| Fe       | plied | with  | \> 3\" | or    | ap     | a      |      |
| rtilizer |       | pl    | by     | in    | plied, | pplied |      |
| App      |       | anter | d      | corpo | no     | on a   |      |
| lication |       | (ba   | isking | rated | i      | field  |      |
| Method** |       | nded) | or     | \<    | ncorpo | with   |      |
|          |       | or    | chis   | 3\"   | ration | s      |      |
|          |       | inj   | eling, | by    |        | urface |      |
|          |       | ected | etc.   | harro |        | runoff |      |
|          |       | \>    |        | wing, |        | (n     |      |
|          |       | 2\"   |        | etc.  |        | atural |      |
|          |       | or    |        |       |        | or     |      |
|          |       | p     |        |       |        | from   |      |
|          |       | lowed |        |       |        | irrig  |      |
|          |       |       |        |       |        | ation) |      |
|          |       |       |        |       |        | and no |      |
|          |       |       |        |       |        | i      |      |
|          |       |       |        |       |        | ncorpo |      |
|          |       |       |        |       |        | ration |      |
+----------+-------+-------+--------+-------+--------+--------+------+
| **Site   | **R   |       |        |       |        |        | **   |
| Characte | ating |       |        |       |        |        | SELE |
| ristic** | and   |       |        |       |        |        | CTED |
|          | Point |       |        |       |        |        | RATI |
|          | Va    |       |        |       |        |        | NG** |
|          | lue** |       |        |       |        |        |      |
+----------+-------+-------+--------+-------+--------+--------+------+
|          | Very  | Low   | Medium | High  | Very   | Cr     |      |
|          | Low   |       |        |       | High   | itical |      |
|          |       | 1     | 2      | 4     |        |        |      |
|          | 0     |       |        |       | 8      |        |      |
+----------+-------+-------+--------+-------+--------+--------+------+
| *        | 0     | \< 40 | 40 -   | 101   | \> 200 |        |      |
| *Organic |       |       | 100    | --    |        |        |      |
| Ph       |       |       |        | 200   | (or    |        |      |
| osphorus |       |       |        |       | un     |        |      |
| App      |       |       |        |       | known) |        |      |
| lication |       |       |        |       |        |        |      |
| Rate     |       |       |        |       |        |        |      |
| (lbs/ac  |       |       |        |       |        |        |      |
| P~2      |       |       |        |       |        |        |      |
| ~O~5~)** |       |       |        |       |        |        |      |
+----------+-------+-------+--------+-------+--------+--------+------+

<table>
<colgroup>
<col style="width: 15%" />
<col style="width: 11%" />
<col style="width: 0%" />
<col style="width: 11%" />
<col style="width: 0%" />
<col style="width: 0%" />
<col style="width: 0%" />
<col style="width: 12%" />
<col style="width: 0%" />
<col style="width: 0%" />
<col style="width: 12%" />
<col style="width: 0%" />
<col style="width: 12%" />
<col style="width: 0%" />
<col style="width: 13%" />
<col style="width: 9%" />
</colgroup>
<tbody>
<tr class="odd">
<td rowspan="2"><strong>Site Characteristic</strong></td>
<td colspan="14"><strong>Rating and Point Value</strong></td>
<td><strong>SELECTED RATING</strong></td>
</tr>
<tr class="even">
<td><p>Very Low</p>
<p>0</p></td>
<td colspan="5"><p>Low</p>
<p>0.75</p></td>
<td><p>Medium</p>
<p>1.5</p></td>
<td colspan="3"><p>High</p>
<p>3</p></td>
<td colspan="2"><p>Very High</p>
<p>6</p></td>
<td colspan="2"><p>Critical</p>
<p>10</p></td>
<td></td>
</tr>
<tr class="odd">
<td><strong>Organic Phosphorus Application Method</strong></td>
<td>None applied</td>
<td colspan="5">Placed with planter (banded) or injected &gt; 2" or
plowed</td>
<td>Incorporated &gt; 3" by disking or chiseling, etc.</td>
<td colspan="3">Chemigated or incorporated &lt; 3" by harrowing,
etc.</td>
<td colspan="2">Surface applied, no incorporation</td>
<td colspan="2">Surface applied on a field with surface runoff (natural
or from irrigation) and no incorporation</td>
<td></td>
</tr>
<tr class="even">
<td rowspan="2"><strong>Site Characteristic</strong></td>
<td colspan="14"><strong>Rating and Point Value</strong></td>
<td><strong>SELECTED RATING</strong></td>
</tr>
<tr class="odd">
<td><p>Very Low</p>
<p>0</p></td>
<td colspan="2"><p>Low</p>
<p>1</p></td>
<td colspan="4"><p>Medium</p>
<p>2</p></td>
<td colspan="3"><p>High</p>
<p>4</p></td>
<td colspan="3"><p>Very High</p>
<p>8</p></td>
<td>Critical</td>
<td></td>
</tr>
<tr class="even">
<td><strong>Nitrogen Application Rate (% of Crop
Requirement)</strong></td>
<td>&lt; 40</td>
<td colspan="2">40 - 60</td>
<td colspan="4">60 - 100</td>
<td colspan="3">100 - 120</td>
<td colspan="3">&gt; 120</td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td rowspan="2"><strong>Site Characteristic</strong></td>
<td colspan="14"><strong>Rating and Point Value</strong></td>
<td><strong>SELECTED RATING</strong></td>
</tr>
<tr class="even">
<td><p>Very Low</p>
<p>0</p></td>
<td colspan="3"><p>Low</p>
<p>0.75</p></td>
<td colspan="4"><p>Medium</p>
<p>1.5</p></td>
<td colspan="3"><p>High</p>
<p>3</p></td>
<td colspan="2"><p>Very High</p>
<p>6</p></td>
<td><p>Critical</p>
<p>10</p></td>
<td></td>
</tr>
<tr class="odd">
<td><strong>Nitrogen Fertilizer Application Method (prior to critical
runoff period)</strong></td>
<td>None applied</td>
<td colspan="2">Placed with planter (banded) or injected &gt; 2" or
plowed</td>
<td colspan="6">Incorporated &gt; 3" by disking or chiseling, etc.</td>
<td colspan="2">Chemigated or incorporated &lt; 3" by harrowing,
etc.</td>
<td colspan="2">Surface applied, no incorporation</td>
<td>Surface applied on a field with surface runoff (natural or from
irrigation) and no incorporation</td>
<td></td>
</tr>
<tr class="even">
<td rowspan="2"><strong>Site Characteristic</strong></td>
<td colspan="14"><strong>Rating and Point Value</strong></td>
<td><strong>SELECTED RATING</strong></td>
</tr>
<tr class="odd">
<td colspan="2"><p>Very Low</p>
<p>0</p></td>
<td colspan="3"><p>Low</p>
<p>0.5</p></td>
<td colspan="4"><p>Medium</p>
<p>1.0</p></td>
<td colspan="2"><p>High</p>
<p>2</p></td>
<td colspan="2"><p>Very High</p>
<p>4</p></td>
<td>Critical</td>
<td></td>
</tr>
<tr class="even">
<td><p><strong>Runoff Index</strong></p>
<p><strong>(Surface Irrigated)</strong></p></td>
<td colspan="2">No runoff occurs</td>
<td colspan="3">-----</td>
<td colspan="4">Water runs off the field less than 50% of the set
time</td>
<td colspan="2">-----</td>
<td colspan="2">Water runs off the field 50% or more of the set
time</td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td><p><strong>Runoff</strong></p>
<p><strong>(Sprinkler Irrigated)</strong></p></td>
<td colspan="2">No runoff occurs</td>
<td colspan="3">Water moves across the surface but not off the
field</td>
<td colspan="4">-----</td>
<td colspan="2">Runoff leaves the field</td>
<td colspan="2">----</td>
<td></td>
<td></td>
</tr>
<tr class="even">
<td><strong>Runoff Class</strong></td>
<td colspan="2">Negligible</td>
<td colspan="3">Very low or low</td>
<td colspan="4">Medium</td>
<td colspan="2">High</td>
<td colspan="2">Very High</td>
<td></td>
<td></td>
</tr>
</tbody>
</table>

<table>
<colgroup>
<col style="width: 15%" />
<col style="width: 11%" />
<col style="width: 0%" />
<col style="width: 0%" />
<col style="width: 11%" />
<col style="width: 0%" />
<col style="width: 0%" />
<col style="width: 12%" />
<col style="width: 0%" />
<col style="width: 13%" />
<col style="width: 12%" />
<col style="width: 13%" />
<col style="width: 9%" />
</colgroup>
<tbody>
<tr class="odd">
<td rowspan="2"><strong>Site Characteristic</strong></td>
<td colspan="11"><strong>Rating and Point Value</strong></td>
<td><strong>SELECTED RATING</strong></td>
</tr>
<tr class="even">
<td><p>Very Low</p>
<p>0</p></td>
<td colspan="3"><p>Low</p>
<p>-1</p></td>
<td colspan="3"><p>Medium</p>
<p>-2</p></td>
<td colspan="2"><p>High</p>
<p>-4</p></td>
<td><p>Very High</p>
<p>-8</p></td>
<td>Critical</td>
<td></td>
</tr>
<tr class="odd">
<td><p><strong>Runoff BMPs</strong></p>
<p><strong>(Only applies if runoff occurs)</strong></p></td>
<td>No conservation practices</td>
<td colspan="3"><p>One or two</p>
<p>on-field conservation practices that reduces runoff</p></td>
<td colspan="3">Multiple conservation practices that reduce runoff
<u>or</u> trap nutrients</td>
<td colspan="2">Multiple conservation practices that reduce runoff
<u>and</u> trap/filter pollutants</td>
<td>Conservation practice(s) that eliminates runoff</td>
<td></td>
<td></td>
</tr>
<tr class="even">
<td rowspan="2"><strong>Site Characteristic</strong></td>
<td colspan="11"><strong>Rating and Point Value</strong></td>
<td><strong>SELECTED RATING</strong></td>
</tr>
<tr class="odd">
<td colspan="2"><p>Very Low</p>
<p>0</p></td>
<td colspan="3"><p>Low</p>
<p>1</p></td>
<td colspan="2"><p>Medium</p>
<p>2</p></td>
<td colspan="2"><p>High</p>
<p>4</p></td>
<td><p>Very High</p>
<p>8</p></td>
<td>Critical</td>
<td></td>
</tr>
<tr class="even">
<td><p><strong>Average Total Soil Erosion due to Water</strong></p>
<p><strong>(tons/ac/year)</strong></p></td>
<td colspan="2">&lt; 1 ton/acre</td>
<td colspan="3">1 - 5 tons/acre</td>
<td colspan="2">5 - 10 tons/acre</td>
<td colspan="2">10 - 15 tons/acre</td>
<td>&gt; 15 tons/acre</td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td rowspan="2"><strong>Site Characteristic</strong></td>
<td colspan="11"><strong>Rating and Point Value</strong></td>
<td><strong>SELECTED RATING</strong></td>
</tr>
<tr class="even">
<td colspan="3"><p>Very Low</p>
<p>0</p></td>
<td colspan="3"><p>Low</p>
<p>1</p></td>
<td colspan="2"><p>Medium</p>
<p>2</p></td>
<td><p>High</p>
<p>4</p></td>
<td><p>Very High</p>
<p>8</p></td>
<td>Critical</td>
<td></td>
</tr>
<tr class="odd">
<td><strong>Distance to Surface Water</strong></td>
<td colspan="3"><p>&gt; 2640 feet</p>
<p>( &gt; 0.5 mile)</p></td>
<td colspan="3">2640 - 1320 feet</td>
<td colspan="2">1319 - 600 feet</td>
<td>599 - 200 feet</td>
<td>&lt; 200 feet</td>
<td></td>
<td></td>
</tr>
<tr class="even">
<td colspan="12"><strong>TOTAL POINTS FOR SURFACE WATER QUALITY (Less
than 12 is a LOW rating)</strong></td>
<td></td>
</tr>
</tbody>
</table>

<table style="width:100%;">
<colgroup>
<col style="width: 15%" />
<col style="width: 11%" />
<col style="width: 0%" />
<col style="width: 11%" />
<col style="width: 0%" />
<col style="width: 12%" />
<col style="width: 0%" />
<col style="width: 12%" />
<col style="width: 0%" />
<col style="width: 12%" />
<col style="width: 0%" />
<col style="width: 13%" />
<col style="width: 9%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="13"></td>
</tr>
<tr class="even">
<td colspan="13"><strong>Ground Water Quality</strong></td>
</tr>
<tr class="odd">
<td rowspan="2"><strong>Site Characteristic</strong></td>
<td colspan="11"><strong>Rating and Point Value</strong></td>
<td><strong>SELECTED RATING</strong></td>
</tr>
<tr class="even">
<td><p>Very Low</p>
<p>0</p></td>
<td colspan="2"><p>Low</p>
<p>1</p></td>
<td colspan="2"><p>Medium</p>
<p>2</p></td>
<td colspan="2"><p>High</p>
<p>4</p></td>
<td colspan="2"><p>Very High</p>
<p>8</p></td>
<td colspan="2">Critical</td>
<td></td>
</tr>
<tr class="odd">
<td><strong>Nitrogen Application Rate (% of Crop
Requirement)</strong></td>
<td>&lt; 40</td>
<td colspan="2">40 - 60</td>
<td colspan="2">60 - 100</td>
<td colspan="2">100 - 120</td>
<td colspan="2">&gt; 120</td>
<td colspan="2"></td>
<td></td>
</tr>
<tr class="even">
<td><strong>Site Characteristic</strong></td>
<td colspan="11"><strong>Rating and Point Value</strong></td>
<td><strong>SELECTED RATING</strong></td>
</tr>
<tr class="odd">
<td><p><strong>Irrigated&gt;</strong></p>
<p><strong>Not Irrigated&gt;</strong></p></td>
<td colspan="2"><p>Very Low</p>
<p>0</p>
<p>0</p></td>
<td colspan="2"><p>Low</p>
<p>0.75</p>
<p>1</p></td>
<td colspan="2"><p>Medium</p>
<p>1.5</p>
<p>2</p></td>
<td colspan="2"><p>High</p>
<p>3</p>
<p>4</p></td>
<td colspan="2"><p>Very High</p>
<p>6</p>
<p>8</p></td>
<td>Critical</td>
<td></td>
</tr>
<tr class="even">
<td><strong>Nitrogen Application Timing</strong></td>
<td colspan="2">None applied</td>
<td colspan="2">Nitrogen applied in several applications during the
primary growing season; the first application no greater than 30 days
from start of primary growing season</td>
<td colspan="2">Majority of nitrogen is applied within 30 days of, or
during, the primary growing season. Nitrogen applied outside this time
frame is less than 50 lbs and is applied with a nitrification inhibitor
or when soil temperatures are less than 50 deg. F.</td>
<td colspan="2">Nitrogen is applied as a single application within 90
days of the primary growing season OR a split application is made which
does not meet the conditions described for LOW or MEDIUM.</td>
<td colspan="2">Nitrogen is applied as a single application more than 90
days prior to the primary growing season.</td>
<td></td>
<td></td>
</tr>
</tbody>
</table>

<table>
<colgroup>
<col style="width: 15%" />
<col style="width: 11%" />
<col style="width: 0%" />
<col style="width: 11%" />
<col style="width: 12%" />
<col style="width: 12%" />
<col style="width: 0%" />
<col style="width: 12%" />
<col style="width: 13%" />
<col style="width: 9%" />
</colgroup>
<tbody>
<tr class="odd">
<td rowspan="2"><strong>Site Characteristic</strong></td>
<td colspan="8"><strong>Rating and Point Value</strong></td>
<td><strong>SELECTED RATING</strong></td>
</tr>
<tr class="even">
<td><p>Very Low</p>
<p>0</p></td>
<td colspan="2"><p>Low</p>
<p>1.5</p></td>
<td><p>Medium</p>
<p>3</p></td>
<td colspan="2"><p>High</p>
<p>6</p></td>
<td><p>Very High</p>
<p>12</p></td>
<td>Critical</td>
<td></td>
</tr>
<tr class="odd">
<td><strong>Irrigation Index</strong></td>
<td>&gt; 79</td>
<td colspan="2">70 - 79</td>
<td>60 - 69</td>
<td colspan="2">50-59</td>
<td>&lt; 50</td>
<td></td>
<td></td>
</tr>
<tr class="even">
<td colspan="10"><strong>This index requires information on the
irrigation system type, water measurement and distribution, irrigation
scheduling, SCI and whether pre- or post-season irrigation is used.
Circle the most appropriate selection in each category.</strong></td>
</tr>
<tr class="odd">
<td colspan="3"><strong><u>Irrigation System</u></strong></td>
<td colspan="3"><strong><u>Irrigation Scheduling</u></strong></td>
<td colspan="4"><strong><u>Water Control and
Measurement</u></strong></td>
</tr>
<tr class="even">
<td colspan="3">Surface - Graded Border</td>
<td colspan="3">Use a set irrigation schedule each year</td>
<td colspan="4"></td>
</tr>
<tr class="odd">
<td colspan="3">Surface - Level Border (Basin)</td>
<td colspan="3">Irrigation based on visual observation of crop
stress</td>
<td colspan="4" rowspan="2">Poor - no water measurement AND poor control
of water due to inadequate water control structures throughout the
conveyance system</td>
</tr>
<tr class="even">
<td colspan="3">Surface - Graded Furrow or Corrugates</td>
<td colspan="3">Soil moisture by NRCS feel method</td>
</tr>
<tr class="odd">
<td colspan="3">Surface - Surge</td>
<td colspan="3">Check book scheduling, irrigation scheduler, etc.</td>
<td colspan="4"></td>
</tr>
<tr class="even">
<td colspan="3">Surface - Controlled with contour ditch, turnouts,
canvas dams, etc.</td>
<td colspan="3">Irrigation scheduling via pan evaporation of atmometer
in field</td>
<td colspan="4" rowspan="2">Fair - manually recorded water measurement
at delivery point to farm AND poor control of water due to inadequate
control structures throughout the conveyance system</td>
</tr>
<tr class="odd">
<td colspan="3">Surface - Uncontrolled (wild flood, no control with
turnouts, etc.)</td>
<td colspan="3">Irrigation scheduling via regional weather network (e.g.
AgriMet)</td>
</tr>
<tr class="even">
<td colspan="3">Sprinkler - Big gun or boom</td>
<td colspan="3">Soil moisture monitoring using Gypsum blocks, moisture
probes, etc.</td>
<td colspan="4"></td>
</tr>
<tr class="odd">
<td colspan="3">Sprinkler - Periodic Move (hand line or wheel line)</td>
<td colspan="3">Continuous measurement of soil moisture, water applied
and ET</td>
<td colspan="4" rowspan="2">Average - manual recordings somewhere in the
system OR good control of water with effective water control structures
throughout the conveyance system</td>
</tr>
<tr class="even">
<td colspan="3">Sprinkler - Solid set</td>
<td colspan="3"></td>
</tr>
<tr class="odd">
<td colspan="3">Sprinkler - Center pivot</td>
<td colspan="3"><strong><u>Pre/Post Irrigation</u></strong></td>
<td colspan="4"></td>
</tr>
<tr class="even">
<td colspan="3">Sprinkler - Lateral/linear move</td>
<td colspan="3">Pre- and post-season irrigations based on standard run
time</td>
<td colspan="4" rowspan="2">Good - manual recordings somewhere in the
system AND good control of water with effective water control structures
throughout the conveyance system</td>
</tr>
<tr class="odd">
<td colspan="3">Micro Irrigation - Sprays and Bubblers</td>
<td colspan="3">Pre-season OR post-season irrigations based on standard
run time</td>
</tr>
<tr class="even">
<td colspan="3">Micro Irrigation - Tubing or tape w/ integrated or
punched-in emitters</td>
<td colspan="3">Pre- and post-season irrigations based on soil moisture
assessment</td>
<td colspan="4"></td>
</tr>
<tr class="odd">
<td colspan="3"></td>
<td colspan="3">Pre- OR post-season irrigations based on soil moisture
assessment</td>
<td colspan="4" rowspan="2">Excellent - Continuous recording water
measurement device(s) AND good control of water with effective water
control structures throughout the conveyance system</td>
</tr>
<tr class="even">
<td colspan="3"></td>
<td colspan="3">No irrigation outside crop growing season</td>
</tr>
<tr class="odd">
<td colspan="3"></td>
<td colspan="3"></td>
<td colspan="4"></td>
</tr>
</tbody>
</table>

<table>
<colgroup>
<col style="width: 15%" />
<col style="width: 11%" />
<col style="width: 0%" />
<col style="width: 10%" />
<col style="width: 0%" />
<col style="width: 12%" />
<col style="width: 0%" />
<col style="width: 12%" />
<col style="width: 0%" />
<col style="width: 12%" />
<col style="width: 0%" />
<col style="width: 13%" />
<col style="width: 0%" />
<col style="width: 1%" />
<col style="width: 8%" />
</colgroup>
<tbody>
<tr class="odd">
<td><strong>Site Characteristic</strong></td>
<td colspan="12"><strong>Rating and Point Value</strong></td>
<td colspan="2"><strong>SELECTED RATING</strong></td>
</tr>
<tr class="even">
<td><p><strong>Irrigated&gt;</strong></p>
<p><strong>Not Irrigated&gt;</strong></p></td>
<td><p>Very Low</p>
<p>0</p>
<p>0</p></td>
<td colspan="2"><p>Low</p>
<p>0.5</p>
<p>1.5</p></td>
<td colspan="2"><p>Medium</p>
<p>1.0</p>
<p>3</p></td>
<td colspan="2"><p>High</p>
<p>2</p>
<p>6</p></td>
<td colspan="2"><p>Very High</p>
<p>4</p>
<p>12</p></td>
<td colspan="2">Critical</td>
<td colspan="3"></td>
</tr>
<tr class="odd">
<td><p><strong>Leaching Index</strong></p>
<p><strong>(Irrigated)</strong></p>
<p><strong>(applies only if Irrigation Index &gt; LOW)</strong></p></td>
<td>&lt; 9</td>
<td colspan="2">9 - 12</td>
<td colspan="2">13 - 16</td>
<td colspan="2">17 - 20</td>
<td colspan="2">&gt; 20</td>
<td colspan="2"></td>
<td colspan="3"></td>
</tr>
<tr class="even">
<td><p><strong>Leaching Index</strong></p>
<p><strong>(Not Irrigated)</strong></p></td>
<td>0</td>
<td colspan="2">0 – 2</td>
<td colspan="2">2 – 5</td>
<td colspan="2">5 – 10</td>
<td colspan="2">&gt;10</td>
<td colspan="2"></td>
<td colspan="3"></td>
</tr>
<tr class="odd">
<td rowspan="2"><strong>Site Characteristic</strong></td>
<td colspan="12"><strong>Rating and Point Value</strong></td>
<td colspan="2"><strong>SELECTED RATING</strong></td>
</tr>
<tr class="even">
<td colspan="2"><p>Very Low</p>
<p>0</p></td>
<td colspan="2"><p>Low</p>
<p>1</p></td>
<td colspan="2"><p>Medium</p>
<p>2</p></td>
<td colspan="2"><p>High</p>
<p>4</p></td>
<td colspan="2"><p>Very High</p>
<p>8</p></td>
<td colspan="2">Critical</td>
<td colspan="2"></td>
</tr>
<tr class="odd">
<td><strong>Water Table/Geologic Feature Depth and Soil
Type</strong></td>
<td colspan="2">Water table or geologic feature &gt; 5 feet from
surface, Hydrologic Group D</td>
<td colspan="2">Water table or geologic feature &gt; 5 feet from
surface, Hydrologic Group C</td>
<td colspan="2">Water table or geologic feature &gt; 5 feet from
surface, Hydrologic Groups A, B</td>
<td colspan="2">Water table or geologic feature &lt; 5 feet to surface,
Hydrologic Groups C, D</td>
<td colspan="2">Water table or geologic feature &lt; 5 feet to surface,
Hydrologic Groups A, B</td>
<td colspan="2"></td>
<td colspan="2"></td>
</tr>
<tr class="even">
<td colspan="14"><strong>TOTAL POINTS FOR GROUND WATER QUALITY (Less
than 9 is a LOW rating)</strong></td>
<td></td>
</tr>
</tbody>
</table>

**Table 2. Surface Water Quality Nutrient Transport Risk Assessment
Index rating and sit e vulnerability.**

  ------------------ ----------- -------------------------------------------
  **Surface Water    **Total**   **Site Vulnerability Chart**
  Risk Assessment                
  Rating**                       

  LOW                \< 12       Low potential for nutrient loss if current
                                 farming practices are maintained.

  MEDIUM             12 - 20     Medium potential for nutrient loss. Some
                                 remediation measures should be undertaken
                                 to minimize the probability of nutrient
                                 loss.

  HIGH               21 - 40     High potential for nutrient loss and
                                 adverse effects on surface and/or ground
                                 waters. Soil and water conservation
                                 measures and phosphorus management plans
                                 are needed to reduce the probability of
                                 nutrient loss.

  VERY HIGH          \> 40       Very high potential for nutrient loss and
                                 adverse effects on surface and/or ground
                                 waters. All necessary soil and water
                                 conservation measures and a nutrient
                                 management plan must be implemented to
                                 minimize nutrient loss.
  ------------------ ----------- -------------------------------------------

**Table 3. Ground Water Quality Nutrient Transport Risk Assessment Index
rating and sit e vulnerability.**

+---------------+------+-----------------------------------------------+
| **Ground      | *    | **Site Vulnerability Chart**                  |
| Water Risk    | *Tot |                                               |
| Assessment**  | al** |                                               |
|               |      |                                               |
| **Index       |      |                                               |
| Rating**      |      |                                               |
+---------------+------+-----------------------------------------------+
| LOW           | \< 9 | Low potential for nutrient loss if current    |
|               |      | farming practices are maintained.             |
+---------------+------+-----------------------------------------------+
| MEDIUM        | 9 -  | Medium potential for nutrient loss. Some      |
|               | 16   | remediation measures should be undertaken to  |
|               |      | minimize the probability of loss.             |
+---------------+------+-----------------------------------------------+
| HIGH          | 16 - | High potential for nutrient loss and adverse  |
|               | 25   | effects on ground water. Soil and water       |
|               |      | conservation measures and nutrient management |
|               |      | plans are needed to reduce the probability of |
|               |      | loss.                                         |
+---------------+------+-----------------------------------------------+
| VERY HIGH     | \>25 | Very high potential for nutrient loss and     |
|               |      | adverse effects on ground water. All          |
|               |      | necessary soil and water conservation         |
|               |      | measures and a nutrient management plan must  |
|               |      | be implemented to minimize loss.              |
+---------------+------+-----------------------------------------------+

+-----------+-----------+-----------+-----------+-----------+-----------+
| **Table   |           |           |           |           |           |
| 4. The    |           |           |           |           |           |
| surface   |           |           |           |           |           |
| RUNOFF    |           |           |           |           |           |
| CLASS     |           |           |           |           |           |
| site      |           |           |           |           |           |
| chara     |           |           |           |           |           |
| cteristic |           |           |           |           |           |
| d         |           |           |           |           |           |
| etermined |           |           |           |           |           |
| from the  |           |           |           |           |           |
| rel       |           |           |           |           |           |
| ationship |           |           |           |           |           |
| of the    |           |           |           |           |           |
| soil      |           |           |           |           |           |
| per       |           |           |           |           |           |
| meability |           |           |           |           |           |
| class and |           |           |           |           |           |
| field     |           |           |           |           |           |
| slope.    |           |           |           |           |           |
| Adapted   |           |           |           |           |           |
| from NRCS |           |           |           |           |           |
| Soil      |           |           |           |           |           |
| Survey    |           |           |           |           |           |
| Manual    |           |           |           |           |           |
| (1993)    |           |           |           |           |           |
| Table     |           |           |           |           |           |
| 3-10.**   |           |           |           |           |           |
+-----------+-----------+-----------+-----------+-----------+-----------+
|           | Soil      |           |           |           |           |
|           | Per       |           |           |           |           |
|           | meability |           |           |           |           |
|           | Class ^1^ |           |           |           |           |
|           |           |           |           |           |           |
|           | *(in/hr)* |           |           |           |           |
+-----------+-----------+-----------+-----------+-----------+-----------+
| Slope (%) | Very      | M         | M         | Slow      | Very Slow |
|           | Rapid     | oderately | oderately |           |           |
|           |           | Rapid and | Slow and  | *(0.06 -  | *(\< 0.06 |
|           | *(\>20.00 | Rapid     | Moderate  | 0.20)*    | in/hr)*   |
|           | in/hr)*   |           |           |           |           |
|           |           | *(2.00 -- | *(0.20 -- |           |           |
|           |           | 20.00)*   | 2.00)*    |           |           |
+-----------+-----------+-----------+-----------+-----------+-----------+
|           | Runoff    |           |           |           |           |
|           | Class     |           |           |           |           |
|           | **^3^**   |           |           |           |           |
+-----------+-----------+-----------+-----------+-----------+-----------+
| Concave   | N         | N         | N         | N         | N         |
| **^2^**   |           |           |           |           |           |
+-----------+-----------+-----------+-----------+-----------+-----------+
| \< 1      | N         | N         | N         | L         | M         |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 1 - 5     | N         | VL        | L         | M         | H         |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 5 - 10    | VL        | L         | M         | H         | VH        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| 10 - 20   | VL        | L         | M         | H         | VH        |
+-----------+-----------+-----------+-----------+-----------+-----------+
| \> 20     | L         | M         | H         | VH        | VH        |
+-----------+-----------+-----------+-----------+-----------+-----------+
|           |           |           |           |           |           |
+-----------+-----------+-----------+-----------+-----------+-----------+

**^1^** Permeability class of the least permeable layer within the upper
39 inches (one meter) of the soil profile. Permeability classes for
specific soils can be obtained from a published soil survey or from
local USDA-NRCS field offices (soils database).

**^2^** Area from which no or very little water escapes by overland
flow.

^**3**^ RUNOFF CLASS: N = negligible, VL = very low, L = low, M =
medium, H = high, VH = very high.

**ATTACHMENT 1: Example for Conservation Planning**

Benchmark condition is sprinkler irrigated potato-sugarbeet-winter wheat
in Southeast Idaho with manure application.

  ------------------------------------------------ ----------------------
                                                   

  Site Characteristic and Ranking                  Factor Weighting X
                                                   Rating Value

  Soil P test is 35 ppm using an Olsen Test = HIGH 1.0 x 4 = 4.0

  P fertilizer application rate is 50 lbs/ac       0.75 x 1 = 0.75
  P~2~O~5~ = LOW                                   

  P fertilizer application method is placed with   0.5 x 1 = 0.5
  planter = LOW                                    

  Organic P source application rate is 210 lbs/ac  1.0 x 8 = 8.0
  = VERY HIGH                                      

  Organic P source application method is           0.75 x 4 = 3.0
  incorporated less than 3 inches by harrowing,    
  etc. = HIGH                                      

  N fertilizer application rate is 80% of crop     1.0 x 2 = 2.0
  requirement prior to debits/credits = MEDIUM     

  N fertilizer application method is broadcast and 0.75 x 1 = 0.75
  incorporated greater than 3" = LOW               

  N fertilizer application timing is single        0.75 x 4 = 3
  application in spring, \> 30 days prior to       
  growing season = HIGH                            

  Irrigation Runoff Index for sprinkler irrigated, 0.5 x 1 = .5
  no runoff occurs but overland flow within field  
  does occur = LOW                                 

  Runoff class from Table 3 is Medium = MEDIUM     0.5 x 2 = 1.0

  No runoff conservation practices in place = VERY 1.0 x 0 = 0
  LOW                                              

  Soil erosion is 7.5 tons/ac/yr = MEDIUM          1.0 x 2 = 2.0

  Distance to nearest receiving water body is 300  1.0 x 4 = 4.0
  feet = HIGH                                      

  Irrigation Index calculated at 68 for center     1.5 x 2 = 3
  pivot with visual observation of crop stress,    
  pre-season irrigation and average control of     
  water = MEDIUM                                   

  Leaching Index for Pocatello = LOW               0.75 x 1 = 0.75

  Water table/soils for Hydrologic Group C with no 1.0 x 1 = 1.0
  water table or geologic feature within 5 feet =  
  LOW                                              

                                                   

  **Total Points for Surface Water Quality**       **26.5**

  **Total Points for Ground Water Quality**        **9.75**
  ------------------------------------------------ ----------------------

**Ranking for Surface Water** - the site has a **HIGH** potential for
nutrient loss and adverse effects on surface waters.

**Ranking for Ground Water --** the site has a **MEDIUM** potential for
nutrient loss and impact to ground water.

**Using the individual site characteristics, identify some factors of
concern and management options that could be used to reduce this site
vulnerability (mitigation):**

**Soil P Test** -- The soil P test was HIGH. Remember that the soil test
level for \"available P\" does not ascertain the total P in the surface
soil. It does, however, give an indication of the amount of total P that
may be present because of the general relationship between the forms of
P and the solution P available for crop uptake. Research has
conclusively shown that the higher the soil test P level of a site, the
proportionately higher the potential P loss will be from that site.
Therefore, the long-term goal should be to conduct a comprehensive soil
testing program on the entire farm and implement nutrient management on
individual fields using OnePlan. Estimates should be made to determine
the time required to deplete the soil P to optimum levels.

**Organic P Source Application Rate** -- The organic P source
application rate was \> 200 lbs/ac, falling in the VERY HIGH category.
This particular site characteristic is especially important. Here we
have a management unit with a soil test P level that is already high and
very high rates of organic P are being applied. Considering the
long-term management options discussed under Soil P Test, the organic P
application rate should either be reduced to crop P uptake or less or no
organic P should be applied until the soil P is depleted back to an
optimal level. The OnePlan nutrient management program can help identify
fields with lower soil P test and lower risk assessment values where the
organic material could be applied.

**Organic P Source Application Method** -- The organic P source
application method was incorporated less than 3 inches with a harrow,
etc. putting it in the HIGH category. Remember that the manner in which
organic P material is applied to the soil can determine potential P
movement. Since the organic P was only minimally incorporated, the
organic P would still have a substantial surface exposure. Mechanical
incorporation reduces the amount of nutrients in the thin mixing zone at
the soil surface and/or on crop residue or foliage, thus reducing the
interaction with and transfer of nutrients to runoff water. With
incorporation, other environmental losses may also be reduced, and
nutrient management may be improved. However, mechanical incorporation
with tillage may reduce soil-protecting crop residue and increase
erosion. Incorporated material may be subject to downward movement.
Leaching losses may be increased, and the relative importance of the
different loss pathways needs to be considered. The organic P material
should be injected or plowed greater than 2 inches, if possible, and
applied immediately before the crop is planted.

**Runoff Conservation Practices** -- No runoff practices are currently
in place, so level of use is VERY LOW. Implementing irrigation water
management and use of surface roughening (dam-dike) and buffers would
help reduce runoff and sediment loss. (see Soil Erosion).

**Soil Erosion** -- The soil erosion rate was 7.5 tons/ac/yr (MEDIUM
category). Prediction models are used in the assessment to indicate a
movement of soil, thus the potential for sediment and attached
phosphorus movement across the slope or unsheltered distance and to a
water body. Conservation measures such as residue management or reduced
tillage should be considered as a way to reduce erosion. In addition,
other conservation measures like field borders or buffers should be
considered as a means to mitigate off-site transport and improve the
quality of runoff leaving the field.

**Irrigation Index --** Despite the use of a center pivot system, the
irrigation index rated MEDIUM because of pre-season irrigation practices
and a low level of irrigation scheduling. Following appropriate
irrigation water management techniques could significantly improve
efficient use of water and reduce the potential for leaching losses.

**Nitrogen Application Timing** -- Applying nitrogen as a single
application more than 30 days prior to the start of the growing season
increases the risk of loss during the spring. Apply the nitrogen closer
to the growing season and consider splitting applications for better
crop use efficiency.