| Project: Development/Publication
of a Manual of "Best Management Practices" for Control of Non-Point Source
Pollution in Washington State |
Project Summary:
Client:
Washington State University Cooperative Extension under a grant by the U.S. Environmental
Protection Agency through the Washington State Department of Ecology
Business:
Development and dissemination of knowledge to improve production agriculture.
Project Objective:
Develop and publicize a manual of "best management practices" for irrigated
agriculture in Washington State that can prevent/control non-point source pollution.
Product Summary
I was
first called into this project to review a previous publication that addressed non-point
source pollution of surface waters. This publication too was a list of so-called
"Best Management Practices" (BMP) that grew out of work that was done with
dairies in mind. The review was to indicate where BMPS intended to prevent/control
non-point source pollution (NPS) of surface waters might result in degradation of ground
waters.
The
second phase was to develop an integrated manual of BMPs which addressed NPS of both
surface and ground waters, pointing out where the trade-offs were likely to occur.
The resulting manual consisted of eight chapters, covering the current situation regarding
NPS in Washington, the regulatory environment, background science of NPS, the BMPs
themselves, where local agencies fit into the picture, and a listing of resources.
An
important decision was not to use the term "Best Management Practice".
Rather the manual was organized around 6 Overall Management Objectives (OMO).
Implementation Practices (IP) were listed that could help each of the OMOs. It was
noted that any one situation would require a different (or a different combination) of
IPs. In summary, every farmer should seek to attain all OMOs, all of the time.
However, different IPs would be used depending on the individual situation.
The
term "best management practice" is undesirable for at least two good reasons.
First, the term is seen within law. That is the phrase "shall use best
available management practices" is seen in laws governing water quality. It is
felt by many that a list of practices labeled as "best management practices"
will then become mandatory rather than discretionary. Second, irrigated agriculture
is not well understood, if understood at all, by many urbanites. Too often it is not
understood that what may be a "BMP" in one situation will not work at all in
another. The problem is not within the phrase "management practice",
rather it is with the term "best".
It was
also noted that the resulting manual was a "living document". That is, as
new science was developed and practical experience achieved, new IPs might be identified,
OMOs re-stated, new ways of applying old IPs identified, or entirely new approaches to
non-point source pollution identified.
The document was also to be a "stand-alone"
reference. That is, the reader would not have to go find one or more other
publications to learn about the background science of NPS, or why any agency had authority
over water quality, or where to go for further help.
Table of Contents
Seen
below is the Table of Contents from the document. This should provide some idea of
the comprehensive nature of the document.
TABLE OF CONTENTSChapter 1 - Introduction
- Organization of Manual
- How to use the Manual
Chapter 2 - Water Quality Issues in Washington State
- Purpose
- Sources and Uses of Water
- Water Quality as an Economic Issue
- Water Quality Law
- Assessment of Water Quality
- Summary of 1992 statewide water quality assessment
- Standards for ground water quality
- Assessment of ground water quality
- Overall Strategy for Reduction of Nonpoint Source Pollution
- Specific Strategy for Protection of Ground Water Quality from Agricultural Activities
- Identification of Practices to Protect Surface and Water Quality
Chapter 3 - Background Science of Water Pollution
- Purpose
- Pollution Process
- Nitrogen as a Potential Pollutant
- Phosphorous as a Potential Pollutant
- Other Nutrients as Potential Pollutants
- Pesticides as Potential Pollutants
- Site Conditions Affecting the Pollution Process
- Irrigation and Rainfall as Detachment and Transport Mechanisms
- Basic Soil-Water-Plant Relationships
- Retention of water by soil
- Volumetric soil water measurement
- Soil water tension
- Soil water characteristic curve
- Management allowed depletion
- Effective root zone
- Evapotranspiration
- Infiltration rate
- Soil water movement/percolation
- Salts, Irrigation and Drainage
- Leaching
- Correcting infiltration and soil structure problems
Chapter 4 - Overall Management Objectives and Implementation Practices
- Purpose
- Increasing On-farm Application Efficiency and the Effects on Water Quality
- Implementing the Practices
- The Manual as a Living Document
- Overall Management Objective 1.00 - Minimize Water Losses in the On-farm Distribution
System
- Explanation and Purpose
- Possible Effects on Water Diversions
- Possible Effects on Crop Yields
- Possible Effects on Ground Water Quality
- Possible Effects on Surface Water Quality
- IP 1.00.01 Install concrete slip-form ditches to replace earthen ditches
- IP 1.00.02 - Convert earthen ditches to pipelines or gated pipe
- IP 1.00.03 - Install flexible membrane linings in earthen ditches or reservoirs
- IP 1.00.04 - Install swelling clays or other engineered material in earthen ditches or
reservoirs
- IP 1.00.05 - Maintain ditches and pipelines to prevent leaks
- Overall Management Objective 2.00 - Improve irrigation system performance and management
in order to minimize deep percolation and surface runoff
- Explanation and Purpose
- Distribution Uniformity and Application Efficiency
- Relationships Between Distribution Uniformity and Application Efficiency
- Effective, Efficient Irrigations
- Presentations of the Implementation Practices in Four Sections
- Other Information Sources
- Possible Effects on Water Diversions
- Possible Effects on Crop Yields
- Possible Effects on Ground Water Quality
- Possible Effects on Surface Water Quality
- Section 1 - Practices for all Irrigation System Types
. IP 2.01.01 - Measure all water applications accurately
. IP 2.01.02 - Monitor pumping plant efficiency
. IP 2.01.03 - Evaluate the irrigation system using SCS or WSU Cooperative Extension
procedures
. IP 2.01.04 - Know required leaching ratios to maintain salt balances
. IP 2.01.05 - Use irrigation scheduling as an aid in deciding when and how much to
irrigate
. IP 2.01.06 - Practice total planning of individual irrigations
. IP 2.01.07 - Use two irrigation systems in special situations (sprinklers for
pre-irrigations then furrows; portable gated pipe to reduce furrow lengths for
pre-irrigations; sprinklers to germinate crops irrigated by micro-irrigation; over-tree
sprinkler for cooling with undertree for irrigation)
.IP 2.01.08 - Consider changing the irrigation system type
.IP 2.01.09 - Use aerial photography to identify patterns that indicate problems with
irrigation/drainage management
- Section 2 - Practices for Surface (Furrow/Rill, Border Strip) Irrigation Systems
. Down-Row Uniformity
. Cross-Row Uniformity
. Soils Variability
. Border Strips
. IP 2.02.01 - Increase furrow flows to maximum non-erosive streamsize if water advance is
too slow
. IP 2.02.02 - Use torpedoes to form a firm, obstruction free channel for furrow flow
. IP 2.02.03 - Use surge-flow techniques
. IP 2.02.04 - Decrease the length of furrow runs
. IP 2.02.05 - Install a suitable field gradient using laser-controlled landgrading where
topsoil depth allows
. IP 2.02.06 - Irrigate a field in two cycles, one cycle with water in the compacted
furrows, one in the uncompacted furrows
. IP 2.02.07 - Drive a tractor with no tools in the uncompacted rows to equalize the
overall infiltration rates in adjacent furrows
. IP 2.02.08 - Use laser-controlled land grading to take out high and low spots in a field
. IP 2.02.09 - Rip hardpans and compacted soil layers to improve infiltration rates
. IP 2.02.10 - Use cutback furrow flows to reduce surface runoff
. IP 2.02.11 - Install runoff-reuse systems
. IP 2.02.12 - Reduce furrow flows to minimum necessary to ensure down-row uniformity if
excess runoff is a problem
. IP 2.02.13 - Control the total application of water
. IP 2.02.14 - Apply water only in every other furrow
- Section 3 - Practices for Sprinkle Irrigation Systems
. Pressure Uniformity
. Device Uniformity
. Wind Effects
. Center Pivots as Exceptions
. IP 2.03.01 - Have an irrigation engineer/specialist check hand-line and side-roll
sprinkle field layouts to ensure correct combinations of spacing, operating pressure,
sprinkler head, and nozzle size/type
. IP 2.03.02 - Have an irrigation engineer/specialist check field layouts for flow
uniformity - use flow control nozzles, pressure regulators as necessary
. IP 2.03.03 - Maintain sprinkle systems in good operating condition
. IP 2.03.04 - Use the "lateral offset" technique with hand-line, side-roll, or
"big gun" field sprinklers to improve overlap uniformity
. IP 2.03.05 - Operate in low-wind situations if possible
. IP 2.03.06 - Modify hand-line and side-roll sprinkle system layouts to smaller spacings
and lower pressures if wind is a problem
. IP 2.03.07 - Ensure that center pivot sprinkler/nozzle packages are matched to the
infiltration rate of the soil
. IP 2.03.08 - Minimize surface runoff from sprinkle-irrigated fields
. IP 2.03.09 - Use reservoir tillage (dammer/diker) techniques with sprinkle systems to
reduce field runoff
. IP 2.03.10 - Install runoff-reuse systems (see IP 2.02.11)
- Section 4 - Practices for Micro-Irrigation Systems
. Pressure Uniformity
. Device Uniformity
. IP 2.04.01 - Consult experienced agronomists/engineers to ensure that the appropriate
volume of soil is being wetted by the system design
. IP 2.04.02 - Have an irrigation engineer/specialist check the design for emission
uniformity (pressure uniformity, correct pressure for the device) -use pressure regulators
and pressure compensating emitters as necessary
. IP 2.04.03 - Have the irrigation water analyzed to enable design of an adequate system
of water treatment and filtration
. IP 2.04.04 - Have a chemical analysis of irrigation water/fertilizer/other additives to
ensure compatibility and prevent clogging of the system
. IP 2.04.05 - Practice good maintenance procedures to ensure that the system performs as
designed
- Overall Management Objective 3.00 - Manage fertilizer program so as to minimize excess
fertilizer available for movement
- Explanation and Purpose
- Possible Effects on Water Diversions
- Possible Effects on Crop Yields
- Possible Effects on Ground Water Quality
- Possible Effects on Surface Water Quality
- IP 3.01.01 - Assess the risk of contamination of ground and surface water due to
fertilizer/chemical leaching or runoff
- IP 3.01.02 - Consider conservation tillage methods to reduce erosion
- IP 3.01.03 - Consider cropping patterns that include deep-rooted crops to scavenge
residual fertilizer
- IP 3.01.04 - Maintain records of all fertilizer tests, cropping rotations, yields, and
applications (dates, material, method, results)
- IP 3.02.01 - Analyze fields for residual fertilizer
- IP 3.02.02 - Analyze irrigation water for nitrogen content
- IP 3.02.03 - Analyze plant tissue to identify fertilizer requirements
- IP 3.02.04 - Test manure or other waste materials for nutrient content
- IP 3.02.05 - Apply seasonal fertilizer requirements with multiple applications
- IP 3.02.06 - Use slow-release nitrogen fertilizers
- IP 3.02.07 - Develop realistic yield goals
- IP 3.03.01 - Calibrate application equipment, including manure spreaders, to apply the
proper, and known, amount
- IP 3.03.02 - Use the appropriate application technique (chemigation, broadcast, banding,
foliar) for the particular situation
- IP 3.03.03 - Schedule fertilizer applications to avoid periods of irrigation for
leaching for salt control, plant cooling, or frost control
- IP 3.03.04 - Avoid wind drift during applications
- IP 3.03.05 - Incorporate surface-applied fertilizers immediately to reduce any
volatilization
- IP 3.03.06 - Utilize nitrification inhibitors in combination with applications of
ammoniacal forms
- IP 3.03.07 - Ensure uniformity of application with manure
- IP 3.03.08 - Do not apply manure to frozen ground, especially sloping fields
- IP 3.03.09 - Analyze irrigation water for compatibility with any fertilizer to be
applied via fertigation
- IP 3.03.10 - Utilize fertigation properly and according to regulations
- Overall Management Objective 4.00 - Manage crop protection program so as to minimize
chemical residues available for transport
- Explanation and Purpose
- IP 4.01.01 - Assess the risk of contamination of ground and surface waters due to
chemical leaching and runoff
- IP 4.01.02 - Practice Integrated Pest Management techniques where applicable
- IP 4.01.03 - Schedule applications for maximum effectiveness
- IP 4.01.04 - Maintain records of all chemicals bought and applied as well as scouts and
individual applications (dates, material, method, crop, results)
- IP 4.01.05 - Read and follow all Label instructions
- IP 4.01.06 - Transport and store chemicals properly
- IP 4.01.07 - Mix and load pesticides properly
- IP 4.01.08 - Store and dispose of used containers properly
- IP 4.01.09 - Maintain equipment properly to reduce spills or leaks and clean properly
after use
- IP 4.01.10 - Clean equipment properly after use
- IP 4.01.11 - Consider conservation tillage methods to reduce erosion
- IP 4.02.01 - Calibrate application equipment
- IP 4.02.02 - Use the appropriate application technique (chemigation, broadcast, air,
ground application)
- IP 4.02.03 - Schedule chemical applications to avoid periods of irrigation for leaching
for salt control, plant cooling, or frost control
- IP 4.02.04 - Analyze irrigation water for compatibility with any chemicals to be applied
via chemigation
- IP 4.02.05 - Utilize chemigation properly and according to regulations
- Overall Management Objective 5.00 - Reduce contamination of surface water from
Sedimentation
- Explanation and Purpose
- Possible Effects on Water Diversions
- Possible Effects on Crop Yields
- Possible Effects on Ground Water Quality
- Possible Effects on Surface Water Quality
- IP 5.01.01 - Use cover crops on unprotected, easily erodible soils
- IP 5.01.02 - Manage crop residues to reduce surface water contamination
- IP 5.01.03 - Install straw mulching in furrows
- IP 5.01.04 - Use reduced tillage (paraplow) cultural systems
- IP 5.01.05 - Use pressed (slicked) furrows with furrow/rill irrigation systems
- IP 5.01.06 - Perform land grading to optimize furrow/rill gradients to reduce soil
erosion
- IP 5.01.07 - Install tailwater drop structures
- IP 5.01.08 - Install buried tailwater drops and collection pipes
- IP 5.02.01 - Install sedimentation pits
- IP 5.02.02 - Install vegetative buffering strips
- IP 5.02.03 - Gather and reuse surface runoff (see IP 2.02.11)
- Overall Management Objective 6.00 - Prevent direct aquifer contamination via wells
- Explanation and Purpose
- Possible Effects on Water Diversions
- Possible Effects on Crop Yields
- Possible Effects on Ground Water Quality
- Possible Effects on Surface Water Quality
- IP 6.00.01 - Complete wells properly where there is the possibility of cascading flows
contaminating a lower aquifer
- IP 6.00.02 - Do not store, load, or mix chemicals near a well head or other vulnerable
place
- IP 6.00.03 - Prevent back siphonage/flow of chemicals or nutrients down a well after
injection
- IP 6.00.04 - Identify and properly seal all abandoned and improperly constructed wells
Chapter 5 - Developing an On-farm Water Quality Program
- Purpose
- Analysis and Planning Procedure
- Determination of current or future water quality problems
- Identification of problem contaminants
- Reducing availability
- Reducing detachment
- Reducing transport
- Determining reasonable goals
- Determining appropriate Implementation Practices and implementation
- Preventing Contamination Problems from Occurring
- Example of Planning Checklist
- Local Area-Wide Information
Chapter 6 - The Role of Government Agencies in Controlling Contamination
- Purpose
- Conservation Districts
- Irrigation Districts
- U.S. Bureau of Reclamation
- Soil Conservation Service
- Washington State University and the Cooperative Extension
- Reacting to Pollution - The Compliance Memorandum of Agreement
Chapter 7 - Resource Guide
Chapter 8 - Glossary
|
Example Implementation Practice
(Below is an example of how
Implementation Practices were presented in the Manual.)
IP 2.01.04 - Know required
leaching fractions to maintain salt balances
Objective
Maintain the viability
of irrigated agriculture while minimizing required deep percolation.
Description
All irrigation water
contains salts. Thus, as irrigations proceed, salt is added to the soil. There
are other sources of salts in the root zone as well. Essentially, the plant will
take up pure water, leaving the salts behind. Over time, with no other management
action, these salts will build up in the soil to the level at which yields are impacted or
cropping options are decreased.
The only way to maintain a
suitable salt balance in the root zone is through leaching, the creation of intentional
deep percolation to carry salts out of the root zone. However, leaching should be
the minimum necessary and the amount of required leaching varies with the irrigation water
quality, soil conditions, and desired cropping rotations.
The irrigation water supply
should be tested for total salts, adjusted SAR, and critical salts such as boron, calcium,
magnesium, and sodium. Consult a qualified agronomist for recommendations on
required leaching fractions or contact the local WSU Cooperative Extension office.
Table 3-1 in Chapter 3 of this Manual contains guidelines for interpreting water quality
tests.
Be aware of the other problems
excess or imbalanced salts can cause:
1. Low soil permeability.
2. Specific crop toxicities.
3. Irrigation system corrosion.
4. Disposal of required leaching
water.
There are several equations in
use for determining required leaching ratios. One commonly used was developed by
Rhodes, et al. and is presented in FAO 29 "Water Quality for Agriculture"
(Westcott and Ayers). It states:
ECe
LF = ----------------------- x
100
(5 * ECe) - ECiw
where:
LF = that percentage of applied
water that must be deep percolation
ECe = the electrical conductivity
of the average saturation extract from the rootzone - this number will usually be assumed
as the maximum salinity allowable before yield reductions will be expected. These
"yield reduction threshold salinities" are listed in a number of
publications. Local agronomic consultants should know the values for crops grown in
their areas.
ECiw = the electrical
conductivity of the irrigation water
SCS National Practice 610
addresses leaching for salt control.
|
Example Text
from Background Science Chapter
(Below is a discussion of nitrogen as a potential contaminant taken from
Chapter 3 of the Manual.
Not seen is a schematic diagram of the "nitrogen cycle".)
The nitrogen
cycle, shown schematically in Figure 3-1, is the name given to the movement of nitrogen in
its different forms from the atmospheric gas N2 into the soil in some form or
another and then back to the atmosphere. Some
of the more important processes that occur are:
1. Fixation - addition of nitrogen to the soil through the symbiotic
action of rhizobia bacteria on the root systems of legumes or by other microorganisms
(non-symbiotic) in the soil and water.
2. Mineralization - the breakdown of soil organic matter by the
activity of microbes Mineralization converts organic nitrogen to the ammonium
(NH4+) form, which is available to the plant.
3. Nitrification - the conversion of the ammonium (NH4+)
form to the nitrate (NO3-) form. Nitrification is the result
of activity by soil bacteria. Nitrate (NO3-) nitrogen is readily
available to plants. However, nitrate (NO3-) nitrogen is also
readily leached since it stays in solution and does not adhere to soil particles.
Nitrification is a relatively quick process. Nitrogen added to the soil via
commercial fertilizer in the ammonium form can be transformed to the nitrate form within
one to two weeks if conditions are favorable.
4. Immobilization - the conversion of inorganic nitrogen in organic matter which occurs when
carbon is added to the soil. Plant residues are the chief source of this
carbon. However, as the decomposition of plant residues continues, nitrogen is again
released through mineralization as explained previously.
5. Denitrification - conversion of nitrate (NO3-)
nitrogen into the atmospheric gas N2 by soil bacteria in wet, poorly aerated
conditions, such as would be found in water-logged, heavy soils. This process can
also occur relatively rapidly but requires decomposing organic matter as a carbon source.
6. Volatilization - the movement of nitrogen in the form of ammonia gas
to the atmosphere. Volatilization occurs when ammonium (NH4+)
forms of nitrogen are applied to the soil surface and not properly worked into the soil.
Volatilization increases with high temperatures and calcareous soils. Lack of
rain following the application and high amounts of crop residue also increase the process.
7. Leaching - the movement of the nitrate (NO3-)
form below the crop's root zone. Both the ammonium (NH4+) and
nitrate (NO3-) forms will leach. However, the nitrate (NH3)
form is highly soluble and thus, is more readily leachable. Leaching occurs with deep
percolation, the movement of soil water below the root zone. Unfortunately, many
times, leachate moves to an aquifer and contaminates ground water.
An example of a path in the nitrogen cycle that includes the use of
commercial fertilizer would be:
1. Conversion of atmospheric N2 into the ammonium (NH4+)
form by a commercial fertilizer manufacturer.
2. Addition of the ammonium (NH4+) fertilizer to
the soil by a grower.
3. Immediate uptake of some of the ammonium (NH4+)
nitrogen by the plant.
4. Nitrification of some of the ammonium (NH4+)
nitrogen into the nitrate (NO3-) form.
5. Uptake by the plant of nitrogen in the nitrate (NO3-)
form.
6. Leaching of the nitrate (NO3-) to ground water
as the result of heavy rainfalls.
7. Reapplication of the nitrate (NO3-) nitrogen
to the field through irrigation water supplied by a deep well pumping from the ground
water.
8. Denitrification of the nitrate (NO3-) nitrogen
back into atmospheric nitrogen gas (N2).
9. Loss of organic nitrogen from the soil by crop harvest.
10. Mineralization of remaining crop organic matter.
Contamination of ground water aquifers by nitrate (NO3-)
nitrogen can be a serious problem in areas of irrigated agriculture due to the large
amounts of nitrogen fertilizer that are normally used to ensure satisfactory yields.
The potential for nitrate contamination depends on several factors:
1. Soil texture and structure - coarse sandy soils do not hold as much
water as finer clays and have higher permeabilities. Thus, any over-irrigation
results in large amounts of leaching water. However, many soils are stratified due
to either different texture (clay lenses) or structure ("plow-pans"). Leaching
may be constrained in the root zone if there are restricting layers.
2. Timing and amount of irrigations and rainfall - over-irrigation, or
unexpected rainfalls create deep percolation, with the concurrent risk of nitrate
leaching. It is important to control irrigations as much as possible.
3. The amount of nitrate (NO3-) nitrogen in the
soil at the time of deep percolation - thus, it is important to minimize the amount of
available nitrate (NO3-) nitrogen, subject to sound agronomic
practices for maintaining yields.
It is important for the grower to know how much nitrogen is needed by
the crop, what stage(s) in the growth cycle this nitrogen is needed, how much nitrogen is
in the soil and the irrigation water and in what form, and how much water is required per
irrigation. |
Non-point Source Pollution
Defined
Non-point source pollution
(NPS) as defined by the Federal Environmental Protection Agency is "...pollution...
caused by diffuse sources that are not regulated as point sources...". Further, the
Washington Legislature has defined non-point source pollution as "pollution that
enters the waters of the State from any dispersed water-based or land-use activities,
including, but not limited to, atmospheric deposition, surface water runoff from
agricultural lands, urban areas, and forest lands, subsurface or underground sources, and
discharges from boats or other marine vessels."
NPS is cumulative in nature. While any one
source of non-point source contamination may be insignificant, the cumulative effect of
many such sources is measurable and can lead to significant pollution of ground or surface
waters. It is difficult, by its nature, to assign responsibility for NPS when it occurs.
NPS is usually the result of land-use
activities. This would include dairies, irrigated and dry land agriculture, logging,
rangeland management, and food processing (disposal of wastes). However, there are other
significant sources of NPS including urban use of chemicals and fertilizers, highway and
railroad maintenance, and naturally occurring contaminants.
NPS is an economic issue. If the degraded
quality of a waterbody prevents a beneficial use, the economic value of that use is lost.
For example, if stream or lake quality is impaired to such a degree that fisheries are not
supported, the economic value of fishing as both recreation and a food supply is lost.
Areas with contaminated ground water are not as attractive to new businesses that might
want to relocate. And, in the worst case, home and land values may be reduced if located
in an area with known water quality problems. Although many times, the values of lost
beneficial uses are difficult to estimate accurately, they must be considered when setting
policy or determining required actions.
The Model of Non-point
Source Pollution
Pollution can be
characterized as the result of a series of processes. These can be generally categorized
as availability, detachment/transformation, and transport. There is a potentially
polluting substance in some amount in some place (availability). The substance can be
separated from where it is supposed to stay (detachment/transformation). The substance is
moved to where it becomes a contaminant (transport). At some level of contamination the
substance becomes a pollutant. Thus, the three main factors in reducing potential
pollution are 1) minimized availability of the potential pollutant in the environment, 2)
minimized detachment of the substance, and 3) minimized transport of the substance.
The Overall Management Objectives, if
achieved, should help to minimize availability, detachment/transformation, and transport
of potential pollutants. Thus, all of the presented Objectives in the Manual should be
achieved all of the time. However, the specific Practices used to achieve the Objectives
will depend on the specific situation.
© Copyright 1998 - Peter Canessa, All Rights Reserved
Page last updated 11/20/99 - Comments/Questions - PWCanessa@aol.com