Idaho Department of Environmental Quality 

SCIENTIFIC BASIS FOR THE CONTROL OF AMMONIA 

FROM DAIRY FARMS BEST MANAGEMENT PRACTICES 

7/18/06 

Ron E. Sheffield, Waste Management Engineer, University of Idaho 

Bruce Louks, Air Quality Division, Idaho Department of Environmental Quality 

This bulletin is to assist dairy farmers in understanding the terms used and the scientific basis for the best 

management practices (BMP) listed in the Idaho Department of Environmental Quality’s Rules for the 

Control of Ammonia from Dairy Farms located at IDAPA 58.01.01.760 through 764 (hereinafter “the 

Rule”). This bulletin will be reviewed annually and revised if necessary to reflect any new information, 

including any changes to the Rule. 

The Rule was developed for dairy farms that emit an estimate of 100 tons per year or more of ammonia. 

The threshold values were derived from manure excretion tables prepared by the American Society of 

Agricultural and Biological Engineers and the USDA – Natural Resources Conservation Service and were 

agreed upon by the Idaho Dairymen’s Association (IDA) and Idaho Conservation League (ICL). In 

addition to manure excretion, the IDA and ICL took into account their best professional judgment to 

account for differences in ammonia losses from various dairy housing types, manure storage systems, 

and land application practices. The table below, located at IDAPA 58.01.01.761, represents the scientific 

findings established in The Dairy Air Emissions Analysis: Focus: Ammonia Emissions for Typical Dairy 

Management Systems in Idaho, February 10-11, 2005. 

SUMMARY: Animal Unit (AU) or mature cow threshold to produce 100 ton NH3/year 

Animal Unit (AU) Basis Drylot Free Stall/Scrape Free Stall/Flush 

 AU (100 t NH3) Threshold 

No land app 7089 3893 

27% volatilization 1 6842 3827 

80% volatilization 2 6397 3700 

2293 

Cow Basis (1400 lbs) Drylot Free Stall/Scrape Free Stall/Flush 

 Total cows (100 t NH3) Threshold 

No land app 5063 2781 

27% volatilization 1 4887 2733 

80% volatilization 2 4569 2643 

1638 

1

 Assumes: Expected level of N->NH3 volatilization for: drop-hose or ground 

 level liquid manure application 2 Assumes: Expected level of N->NH3 volatilization for: center pivot or other 

conventional sprinkler irrigation liquid manure application 

Best Management Practices 

The Rule recognizes that dairy farms are unique and that no specific BMP is appropriate for all dairy 

farms. Therefore, Section 764 of the Rule contains a table of BMP options. The dairy farmer must 

implement at least 27 points worth of BMPs under its permit by rule. 

During the development of the Rule, various manure treatment systems and handling practices were 

evaluated for their effectiveness in reducing ammonia emissions. Many scientific studies, extension 

bulletins, NRCS handbooks and EPA guidance documents were referred to in preparing the professional 

judgment toward relative effectiveness in reducing ammonia and the allocation of points. An arbitrary 

point system, with a maximum of 20 points, was assigned to each practice; whereas, a practice receiving 
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20 points would equate to a system or practice that would result in a major reduction, approximately 70 

percent, in ammonia emissions for that specific process. Each practice was rated on a year-round basis 

and as if all of the manure practically available for the practice was handled by the practice and variations 

due to normal seasonal use of each practice was taken into account in the points awarded to each BMP. 

Variations due to seasonal practices (such as corral harrowing or direct land application of liquid manure) 

and expected weather conditions have been factored into these ratings. Points awarded to land 

application practices assume that the practice is utilized on all manure that is applied. Points are allowed 

to be pro-rated to reflect actual waste treatment or handling that is occurring on each farm. 

The emissions related to the management of exported manure are also addressed in the Rule. Dairy 

farmers, under the Rule, can “take credit” for the management of ammonia conservation practices that 

occur on farms (3rd parties) that receive their manure. For example, if a dairy exports all the vacuumed 

slurry (feces and urine) from a freestall dairy to a neighboring farm which injects the manure, a total of 25 

points would be awarded: 15 for “Direct Utilization of Collected Slurry” and 10 points for “Soil Injection – 

Slurry,” if used year-round or pro-rated to reflect the percentage of the year used. In order to take credit 

for activities conducted by 3rd parties, dairy farmers must keep records on the amount of exported 

material that left the farm and the BMP the 3rd party intends to employ. 

The list of BMPs was developed to give the maximum amount of flexibility for producers to select the 

appropriate ammonia control practices for their farm. Producers should review the description of BMPs 

found in this bulletin as well as discuss their proposed plan with their Nutrient Management Planner to 

ensure that the proposal is not contrary to the provisions of their nutrient management plan. 
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Section 764 states: 

Ammonia Control Practices for Idaho Dairies 

 Ammonia Control Effectiveness 1

System Component 

Open 

Lot Freestall Scrape 

Freestall 

Flush 

Compliance 

Method3

 

Waste Storage and 

Treatment Systems Synthetic Lagoon Cover 15 20 20 1 

 GeoteXtile Covers 10 13 13 1 

 Solids Separation 3 3 3 3, 4 

 Composting 4 4 4 1 

 

Separate Slurry and Liquid Manure 

Basins 6 10 - 1 

 In-House Separation 0 12 0 1 

 Direct Utilization of Collected Slurry 6 10 - 1, 3, 4 

 Direct Utilization of Parlor Wastewater 10 10 10 1 

 Direct Utilization of Flush Water 8 0 13 3, 4 

 Anaerobic Digester - - - - 

 Anaerobic Lagoon - - - - 

 Aerated Lagoon 10 12 15 2 

 Sequencing-Batch Reactor 15 20 20 2 

 

Lagoon Nitrification/Denitrification 

Systems 15 20 20 2 

 Fixed-Media Aeration Systems 15 20 20 2 

 

General Practices 

Vegetative or Wooded Buffers 

(established) 7 7 7 1 

 

Vegetative or Wooded Buffers 

(establishing) 2 2 2 1 

 Alternatives to Copper Sulfate - - - - 

 

Freestall Barns Scrape Built Up Manure - 3 3 1 

 Frequent Manure Removal UD UD UD - 

 Tunnel Ventilation - - - - 

 Tunnel Ventilation w/Biofilters - 10 10 1 

 Tunnel Ventilation w/Washing wall - 10 10 3, 4 

 

Open Lots and 

Corrals Rapid Manure Removal 4 2 2 1, 2 

 Corral Harrowing 4 2 2 1 

 Surface Amendments 10 5 5 2 

 In-Corral Composting / Stockpiling 4 2 2 1 

 Summertime Deep Bedding 10 5 5 1 
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System Component Ammonia Control Effectiveness 1 

Compliance 

Method3

 Open Lot Freestall Scrape 

Freestall 

Flush 

 

Composting 

Practices Alum Incorporation 12 8 6 2 

 

Carbon:Nitrogen Ratio (C:N) Ratio 

Manipulation 10 7.5 5 2 

 Composting with Windrows - - - - 

 Composting Static Pile 6 4.5 3 1 

 Forced Aeration Composting 10 7.5 5 1 

 

Forced Aeration Composting with 

Biofilter 12 8 6 1 

 

Land Application2 Soil Injection - Slurry 10 15 7.5 2 

 Incorporation of manure within 24 hrs 10 10 10 2 

 Incorporation of manure within 48 hrs 5 5 5 2 

 Nitrification of lagoon effluent 10 10 15 3, 4 

 

Low Energy/Pressure Application 

Systems 7 7 10 1 

 Freshwater Dilution 5 8 8 1, 2 

 Pivot Drag Hoses 8 8 10 1 

 Subsurface Drip Irrigation 10 10 12 1 

 

Notes: 

1. The ammonia emission reduction effectiveness of each practice is rated numerically based on practical year-round implementation. Variations due to 

seasonal practices and expected weather conditions have been factored into these ratings. Not implementing a BMP when it is not practicable to do so, 

does not reduce the point value assigned to the BMP, nor does it constitute failure to perform the BMP. UD indicates that the practice is still under 

development. 

2. Land application practices assume practice is conducted on all manure; points will be pro-rated to reflect actual waste treatment; points can be 

obtained on exported material with sufficient documentation. 

3. Method used by inspector to determine compliance: 

 1=Observation by Inspector 

 2=On-Site Recordkeeping Required 

 3, 4=Deviation Reporting Required. Equipment upsets and/or breakdowns shall be recorded in a deviation log and if repaired in a reasonable 

 timeframe does not constitute non-compliance with this rule. 

A description of each ammonia control BMP is attached hereto as Appendix A. 

How do I calculate how many BMP points I have? 

Dairy farmers subject to this Rule should review the list of accepted BMPs and denote which practices 

they use throughout the year to manage and land apply the manure on their farm. The plan should reflect 

the “year-around” implementation of practices, rather than a plan for summer BMPs and another for 

winter BMPs. The following three examples, using the same example dairy farm, will help in determining 

the amount of points that should be awarded for each farm. 

Example Dairy

Sweet Cream Dairy is a 2,200 freestall facility that scrapes the manure into a collection pit. The manure 

solids are then separated using a screw press and are windrowed and “composted” for bedding, while the 

liquid is stored in the lagoon. Wastewater from the parlor and holding pen is separated using a solids 

settling basin and the liquid drains into the lagoon. Exercise pens for the lactating cows are harrowed 
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daily, when weather permits. Lagoon wastewater is applied during the growing season using two center 

pivots, using overhead sprinklers, and 4 wheel-lines. The dairy also cleans up “unauthorized” manure 

from around the barns, separators, and irrigation equipment weekly. The dairy works with their nutritionist 

to monitor excess nitrogen through weekly milk urea nitrogen (MUN) samples. No replacement heifers or 

calves are kept on the facility. 

Example #

1

Initial BMP Point Determination: 

• Composting: 4 points 

Separated solids from screw press and the settling basin are “composted” or dried without 

supplemental carbon sources or using rapid composting methods 

• Scrape Built Up Manure: 3 points 

Weekly clean-up of “unauthorized” manure from around the barns, separators, and 

irrigation equipment 

• Corral Harrowing: 2 points 

Farm daily harrows of exercise pens, when weather permits, and remove excess manure 

as necessary 

• Manage Dietary Protein: 2 points 

Working with a trained nutritionist to monitor ration for excess nitrogen through the review 

of milk urea nitrogen (MUN) samples 

• Total Points = 11 points

Example #

2

Sweet Cream Dairy understands it does not have enough points to meet the 27 points required. 

Reviewing their options with their Nutrient Management Planner, the dairy farm considers directly 

composting the collected slurry from the freestall barn with imported mint tailings and straw. 

BMP Point Determination for directly composting collected slurry: 

• Direct Utilization of Collected Slurry: 10 points 

As an alternative to storing the slurry in the lagoon, the collected slurry is incorporated into 

compost 

• Carbon:Nitrogen Ratio (C:N) Manipulation: 7.5 points 

Mint tailings and straw are used as carbon sources for the collected slurry. In addition to 

drying the slurry, the high carbon content helps to conserve ammonia (nitrogen) within the 

compost pile 

• Previous points: 11 points 

• Total Points = 28.5 points

Example #

3

Rather than composting the collected slurry, Sweet Cream Dairy has contracted with several 

neighboring farms (3rd party receivers) to receive their manure daily during 8 months of the year. 

Additionally, the dairy farm hires a local hauler to inject the manure on fields specified by his 

neighbors. During the remaining 4 months of the year, the collected slurry is separated and the 

liquids are stored in the lagoon. 

BMP Point Determination for directly injecting collected slurry: 

• Direct Utilization of Collected Slurry: 10 x .75 = 7.5 points 

As an alternative to storing the slurry in the lagoon during 8 months of the year, the scraped 

slurry is exported off the farm. Points are pro-rated to reflect 8-month implementation 

• Soil Injection – Slurry: 15 points x .75 = 11.25 

Manure is injected into the soil at a depth of 2 inches or greater. Points are pro-rated to 

reflect 8 month implementation 

• Previous points: 11 points 

• Total Points = 29.75 points
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What if I only do a BMP for part of the year? Do I get full credit? 

If the BMP can be conducted/implemented year-around, then no, the points would need to be pro-rated to 

reflect the number of months in which it will be used. This is the case in Example #3 where the amount of 

points were reduced by 25% to reflect that the collected slurry was exported for only 8 months of the year. 

If the practice is seasonal in nature, like corral harrowing, the total number of points would be awarded 

because the season reduction has already been taken into account when the points were assigned. 

For more information, please contact 

Dr. Ron Sheffield 

Waste Management Engineer 

University of Idaho Extension 

208-736-3625 rons@uidaho.edu 

Marv Patten 

Dairy Bureau Chief 

Idaho Department of Agriculture 

208-332-8550 mpatten@idahoag.us 

Martin Bauer 

Air Quality Division Administrator 

Idaho Department of Environmental Quality 

208-373-0440 Martin.Bauer@deq.idaho.gov 
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Appendix A 

AMMONIA CONTROL BMPS 

LIQUID MANURE STORAGE AND TREATMENT

Synthetic Lagoon Cover. 

Definition: Impermeable lagoon cover constructed of flexible polyvinyl chloride (PVC) or high 

density polyethylene (HDPE). Creates an air and water tight seal over the manure 

surface. Requires a vent to release carbon dioxide and methane. 

Points: Open Lot - 15 points; Freestall Scrape – 20 points; Freestall Flush – 20 points 

 In general, open lot receives fewer points because of the relative amount of manure 

that would potentially go into the liquid storage structure. 

Compliance: Observation. 

 Either present or not; recording and reporting not required. Inspector will have 

discretion if cover has a tear to decide if the size of the tear is affecting practice; dairy 

will be required to repair to maintain BMP points. 

Management 

Considerations: Cover will result in the accumulation of nitrogen within the lagoon. Manure samples 

should be taken to ensure that excess nitrogen is applied to crops at appropriate 

rates. Vent and/or flare is required to release collected carbon dioxide and methane, 

Geotextile Cover.

Definition: Permeable cover constructed of non-woven synthetic felt. Constructed to provide 

complete coverage over liquid surface. 

Points: Open Lot - 10 pts; Freestall Scrape – 13 pts; Freestall Flush – 13 pts 

 In general, open lot receives fewer points because the relative amount of liquid 

storage is less than with the freestall. 

Compliance: Observation. 

 Either present or not; no recording, no reporting would be required. Inspector will 

have discretion if cover has a tear to decide if tear was affecting practice; dairy will be 

required to repair or loose points. 

Management 

Considerations: Cover will result in the accumulation of nitrogen within the lagoon. Manure samples 

should be taken to ensure that excess nitrogen is applied to crops 

Solids Separation. 

Definition: Gravity or mechanical separation system to remove manure solids from liquid waste 

stream. Separation pits should be cleaned on a regular basis with holding times less 

than one month. Separated solids from mechanical systems should be removed 

from the separator on a regular basis, not to exceed three days. 

Points: Open Lot - 3 points; Freestall Scrape – 3 points; Freestall Flush – 3 points 

Compliance: Recordkeeping - deviation log. Maintain a one-time plan or explanation of system 

used and how cleaning is done. Maintain a deviation log to document 

noncompliance with plan. 
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Composting.

Definition: Stacking and drying of separated manure solids or corral manure. Practice may or 

may not meet the carbon-to-nitrogen ratio criteria specified in Natural Resources 

Conservation Service Standard #317. 

Points: Open Lot - 4 points; Freestall Scrape – 4 points; Freestall Flush – 4 points 

Compliance: Observation.

Management 

Considerations: Composting is a aerobic biological process that results in the degradation of organic 

materials. For optimum composting conditions the carbon to nitrogen ration (C:N) 

should be between 30 – 40:1, and the moisture content should be between 50 – 60% 

moisture. No special microbes are required for sufficient composting. 

Separate Slurry and Liquid Manure Basins.

Definition: Construction and use of separate holding basins/lagoons to keep parlor wastewater 

and corral runoff away from concentrated slurry (manure and urine). Applicable 

systems would include freestall scrape and open lot dairies, which scrape their 

feeding alleys. 

Points: Open Lot - 6 points; Freestall Scrape – 10 points; Freestall Flush – 0 points 

 In general, open lot receives fewer points because the relative amount of liquid 

storage is less than the freestall scrape. 

Compliance: Observation. 

In-House Separation.

Definition: Specialized floor design allowing fecal material to remain in place while urine is 

removed. 

Points: Open Lot – 0 points; Freestall Scrape – 12 points; Freestall Flush – 0 points 

Compliance: Observation 

Management 

Considerations: This practice utilizes floor designs which will segregate urine and feces from 

collecting in the same area within the freestall barn. Ammonia emissions are 

reduced through minimizing contact of time of urine and feces resulting in the 

conversion of urea to ammonia. 

Direct Utilization of Collected Slurry.

Definition: Year-round utilization or direct application of manure slurry instead of placing 

collected fresh material in storage basis - includes on-farm and export systems. 

Direct utilization means slurry wastewater is not sent to a wastewater storage basin 

with the exception of a collection pit. Seasonal systems (daily during the growing 

season) need to pro-rate points to reflect the number of months in which the process 

is conducted. 

Points: Open Lot - 6 points; Freestall Scrape – 10 points; Freestall Flush – 0 points 

Compliance: Observation when it is working; may need deviation log in the winter time when it is 

not land applied. 
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Management 

Considerations: Daily application systems should consult a nutrient management planner or a 

Certified Crop Advisor. Practice also includes facilities which incorporate collected 

slurry directly into compost windrows. 

Direct Utilization of Collected (Parlor) Wastewater.

Definition: Utilization or direct application of parlor wastewater during the active growing season

instead of placing collected fresh wastewater in storage basin - includes on-farm and 

export systems. Direct utilization means that parlor wastewater is not sent to a 

wastewater storage basin. Wastewater may be stored in a temporary storage (<5 

days) until it is utilized and applied daily during the growing season as weather 

conditions allow. 

Points: Open Lot - 10 points; Freestall Scrape – 10 points; Freestall Flush – 10 points 

Compliance: Observation.

Management 

Considerations: Daily application systems should consult a nutrient management planner or a 

Certified Crop Advisor and consider mixing wastewater with irrigation water during 

application. 

Direct Utilization of Flush Waste.

Definition: Utilization or direct application of flush water during the active growing season

instead of placing collected flush water in storage basin. Applicable systems would 

include freestall flush and open lot flush alley systems. Wastewater may be stored in 

a temporary storage (<5 days) until it is utilized and applied daily during the growing 

season as weather conditions allow. 

Points: Open Lot - 8 points; Freestall Scrape – 0 points; Freestall Flush – 13 points 

Compliance: Observation. 

Management 

Considerations: Daily application systems should consult a nutrient management planner or a 

Certified Crop Advisor and consider mixing wastewater with irrigation water during 

application. 

Anaerobic Digester.

Definition: Treatment systems which anaerobically digests organic matter from the manure and 

converts it into methane using bacteria. The methane is then collected and may be 

used to generate electricity or as an alternative to natural gas. Steady supply of 

manure is needed - typically no change to nutrient concentration without additional 

treatment - also effective in reducing volatile organic compounds, biological oxygen 

demand, and odor. 

Points: Open Lot - 0 points; Freestall Scrape – 0 points; Freestall Flush – 0 points 

 

Compliance: None 

Management 

Considerations: No points assigned because anaerobic digestion converts organic-nitrogen to 

ammonia-nitrogen. However, digestion allows for additional treatment to be 

conducted at lower operational costs. 

Anaerobic Lagoon. 
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Definition: Biological earthen basis which manure is designed to decompose liquid manure 

without the presence of oxygen. System has a pH of 7.0 to 8.0, and sludge is 

designed to be removed every 5 years. Also effective in reducing volatile organic 

compounds, biological oxygen demand, and odor. 

Points: Open Lot - 0 points; Freestall Scrape – 0 points; Freestall Flush – 0 points 

 No points assigned because this is not an ammonia control. 

Compliance: None 

Management 

Considerations: No points assigned because anaerobic digestion converts organic-nitrogen to 

ammonia-nitrogen. However, digestion allows for additional treatment to be 

conducted at lower operational costs. 

Aerated Lagoon.

Definition: Biological treatment basin designed to decompose liquid manure and nitrify ammonia 

in the presence of oxygen. System has a pH of 7.0 to 8.0, and sludge is designed to 

be removed every 5 years. Systems should utilize submerged micro-bubble systems 

to reduce ammonia loss. If engineering guidelines are not specified by the designer, 

system should be operated to maintain a dissolved oxygen concentration greater 

than 1.5 mg/l and an oxygen-reduction-potential (ORP) greater than 50. Quarterly 

monitoring of inflow and outflow nitrogen species is required to track system 

performance. Also effective in reducing volatile organic compounds, biological 

oxygen demand, and odor.

Points: Open Lot - 10 points; Freestall Scrape – 12 points; Freestall Flush – 15 points 

 Point differences are based on the amount of material to be treated. 

Compliance: Recordkeeping, Reporting Required - sensor for dissolved oxygen, oxygen-reductionpotential level; quarterly monitoring of the inflow/outflow 

Management 

Considerations: Operational cost for lagoon aeration can be significant. 

Sequencing Batch Reactor. 

Definition: Single tank treatment system that allows for the sequencing of anaerobic, anoxic and 

aerobic conditions within the tank through the scheduling of wastewater feeding and 

aeration. Successful systems have been documented to reduce 85% of total 

nitrogen for animal wastewater. Quarterly monitoring of inflow and outflow nitrogen 

species is required to track system performance. Also effective in reducing volatile 

organic compounds, biological oxygen demand, and odor. 

Points: Open Lot - 15 points; Freestall Scrape – 20 points; Freestall Flush – 20 points 

 More points are given than aerated lagoon because of higher efficiency and 

operational control. 

Compliance: Recordkeeping and reporting required. Seasonal monitoring of inflow/outflow will be 

needed. 

Management 

Considerations: Operational cost for SBR can be high, but achieves an environmentally friendly 

reduction of nitrogen. 

Lagoon Nitrification and Denitrification System. 
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Definition: Engineered lagoon modification or stand-alone system designed and operated to 

convert wastewater ammonia to nitrate and then to nitrogen gas. Quarterly 

monitoring of inflow and outflow nitrogen species is required to track system 

performance. Also effective in reducing volatile organic compounds, biological 

oxygen demand, and odor. 

Points: Open Lot - 15 points; Freestall Scrape – 20 points; Freestall Flush – 20 points 

Compliance: Recordkeeping and reporting required. Seasonal monitoring of inflow/outflow will be 

needed. 

Management 

Considerations: Operational cost for lagoon system can be high, but achieves an environmentally 

friendly reduction of nitrogen while potentially utilizing the existing earthen storage 

basin. 

Fixed Media Aeration System. 

Definition: Stand-alone treatment system designed and operated to convert wastewater 

ammonia to nitrate. Systems utilize a media or substrate on which to propagate 

bacterial growth. Several systems have been shown to denitrify wastewater nitrate 

into nitrogen gas. Quarterly monitoring of inflow and outflow nitrogen species is 

required to track system, performance. Also effective in reducing volatile organic 

compounds, biological oxygen demand, and odor. 

Points: Open Lot - 15 points; Freestall Scrape – 20 points; Freestall Flush – 20 points 

Compliance: Recordkeeping and reporting required. Seasonal monitoring of inflow/outflow will be 

needed. 

Management 

Considerations: Operational cost for fixed media aeration systems are moderate compared to other 

aeration systems. Several systems have been shown to achieve an environmentally 

friendly reduction of nitrogen while reducing odor potential of treated wastewater.

GENERAL PRACTICES

Vegetative or Wooded Buffers – Established/Establishing. 

Definition: Mixture of hardwood and evergreen trees or shrubs control, capture, and mix higher 

elevated cleaner air with lower, dust and odor laden air from the ground surface. 

Also effective on odor, and dust. Should be installed between production 

facility/lagoon and neighbors. (Established: At mature growth stage; Establishment: 

Planted but not at manure growth stage.) 

Points: 

(Established) Open Lot – 7 points; Freestall Scrape – 7 points; Freestall Flush – 7 points 

(Establishment) Open Lot – 2 points; Freestall Scrape – 2 points; Freestall Flush – 2 points 

Compliance: Observation 

Management 

Considerations: NRCS Standard 380 “Windbreak/Shelterbelt Management” should be used as a 

guide for establishment.

Alternatives to Copper Sulfate. 
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Definition: Use of approved alternatives to copper sulfate as a hoof treatment and preventative 

measure. No effect on ammonia; significant reduction in hydrogen sulfide. 

Points: Open Lot - 0 points; Freestall Scrape – 0 points; Freestall Flush – 0 points 

Compliance: None 

Management 

Considerations: However effective alternatives to copper sulfate will be in reducing odors from dairy 

storage basins, no direct correlation to reductions in ammonia emission have been 

established 

FREESTALL BARNS

Scrape Built Up Manure. 

Definition: Removal of build up manure around the yard and manure handling system. Specific 

emphasis on ends of barns, around collection pits, mixing tanks and manure loading 

areas. Also effective in reducing odors and fly production. 

Points: Open Lot - 0 points; Freestall Scrape – 3 points; Freestall Flush – 3 points 

Compliance: Observation 

Frequent Manure Removal. 

Definition: Practice is under evaluation at the University of Idaho and Texas A&M. No 

recommendation at this time. 

Points: Under Development 

Compliance: Under Development 

Management 

Considerations: The effect of manure removal timing on ammonia emissions is currently showing 

mixed results. 

Tunnel Ventilation. 

Definition: Engineered mechanical ventilation system which draws fresh air into a barn through 

an open end wall by a slight negative pressure that is created by exhaust fans 

mounted at the opposite end wall. 

Points: Open Lot - 0 points; Freestall Scrape – 0 points; Freestall Flush – 0 points 

Compliance: None 

Tunnel Ventilation with Biofilter. 

Definition: Tunnel ventilation system that exhausts air into a biological biofilter for air treatment. 

Biofilter material should contain 50% shredded wood and 50% finished compost. 

System is also effective in reducing hydrogen sulfide, odor, and dust from barns. 

Points: Open Lot - 0 points; Freestall Scrape – 10 points; Freestall Flush – 10 points 

Compliance: Observation 

Management 
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Considerations: Although not currently demonstrated on a dairy facility, this practice has shown 

significant reductions in ammonia, hydrogen sulfide, and odor emissions from swine 

facilities.

Tunnel Ventilation with Washing Wall. 

Definition: Tunnel ventilation system that exhausts air into engineered washing wall for air 

treatment. Washing wall is designed to remove ammonia and dust from barn using a 

cascade of recycled water. Water may be acidified to increase ammonia removal. 

Systems are also effective in reducing odor and dust from barns. 

Points: Open Lot - 0 points; Freestall Scrape – 10 points; Freestall Flush – 10 points 

Compliance: Deviation Log 

Management 

Considerations: Although not currently demonstrated on a dairy facility, this practice has shown 

significant reductions in ammonia, dust, and odor emissions from swine facilities.

OPEN LOTS AND CORRALS

Rapid Manure Removal. 

Definition: Removal of winter time manure and corral bedding from open lot surface in spring or 

as quickly as practicable. Manure can then be stockpiled, composted or exported off 

of the dairy. 

Points: Open Lot - 4 points; Freestall Scrape – 2 points; Freestall Flush – 2 points 

Compliance: Observation - if the inspector is present when removal is being done; Recordkeeping 

- if the inspector is not present when removal is being done 

Corral Harrowing. 

Definition: Corral harrowing to distribute deposited manure, reshape corral surface and/or 

remove manure from corral surface. Harrowing should be conducted no less than 

three times per week when weather conditions permit. 

Points: Open Lot - 4 points; Freestall Scrape – 2 points; Freestall Flush – 2 points 

Compliance: Observation 

Surface Amendments. 

Definition: Use of liquid and dry chemical products that will bind or chemically target the 

conversion of urea to ammonia gas. Produce effectiveness and described use should 

be specified by manufacture testing. Examples of product may include, but are not 

limited to: alum, magnesium sulfate, acids. 

Points: Open Lot - 10 points; Freestall Scrape – 5 points; Freestall Flush – 5 points 

Compliance: Recordkeeping – documented with receipts for amendment orders 
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Management 

Considerations: This practice does not include biological amendments or bacterial stimulants. 

Producers should consult their nutrient management planner to review the effect of 

any product on agronomic performance.

In-Corral Composting/Stockpiling. 

Definition: Stockpiling and subsequent drying and potential decomposition of winter manure and 

bedding in-corral through summer and fall. Practice encourages the timely stacking 

and cleaning of corral surfaces. Practice cannot receive additional points through 

carbon-to-nitrogen ratio manipulation. 

Points: Open Lot - 4 points; Freestall Scrape – 2 points; Freestall Flush – 2 points 

Compliance: Observation 

Summertime Deep Bedding.

Definition: Six inches of straw on an open corral surface as a one-time application. An 

approximate 40% reduction in ammonia emission is achieved. 

Points: Open Lot – 10 points; Freestall Scrape – 5 points; Freestall Flush – 5 points 

Compliance: Observation 

Management 

Considerations: This practice allows a layer of straw to segregate urine and feces from collecting in 

the same area within the open lot. Feces deposited on straw will be allowed to dry 

and thus shed liquids if urinated upon. Ammonia emissions are reduced through 

minimizing contact of time of urine and feces resulting in the conversion of urea to 

ammonia. 

 Special management will need to be taken to manage fly production within lot.

ANIMAL NUTRITION

Manage Dietary Protein. 

Definition: With the assistance of a professional nutritionist, develop and follow a strategy to 

feed closer to National Research Council guidelines and production requirement, 

incorporate phase feeding or use of appropriate amino acids or enzymes. 

Points: Open Lot - 2 points; Freestall Scrape – 2 points; Freestall Flush – 2 points 

Compliance: Recordkeeping – documented with milk urea nitrogen analysis and receipts from 

protein orders 

Management 

Considerations: Producers should consult their nutritionist to evaluate the level of nitrogen in the 

rations fed on the farm. 
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15

COMPOSTING PRACTICES

Alum Incorporation. 

Definition: Regular incorporation of aluminum sulfate with fresh material to reduce ammonia 

volatilization. Dissolved phosphorus will also be reduced in the applied product. 

Points: Open Lot - 12 points; Freestall Scrape – 8 points; Freestall Flush – 6 points 

Compliance: Recordkeeping – documented with receipts 

Management 

Considerations: This practice does will increase the nitrogen content of the applied compost. 

Producers should consult their nutrient management planner to review the effect of 

any product on agronomic performance.

Carbon-to-Nitrogen Ratio Manipulation. 

Definition: Management and material selection to insure that the carbon-to-nitrogen ratio is 

greater than 35:1 in the finished compost material. Lower carbon-to-nitrogen ratios 

will encourage greater ammonia volatilization. Practice should not be allocated 

toward "In-Corral Composting/Stockpiling." 

Points: Open Lot - 10 points; Freestall Scrape – 7.5 points; Freestall Flush – 5 points 

Compliance: Recordkeeping 

Management 

Considerations: Composting is a aerobic biological process that results in the degradation of organic 

materials. For optimum composting conditions the carbon to nitrogen ration (C:N) 

should be between 30 – 40:1, and the moisture content should be between 50 – 60% 

moisture. Adding supplemental carbon sources will also increase porosity within the 

compost pile allowing for better aeration within the pile. No special microbes are 

required for sufficient composting.

Composting with Windrows. 

Definition: Aerobic decomposition of manure or other organic materials placed in long rows. 

The windrows can be actively turned, passive, actively aerated windrow, or passively 

aerated windrow. Temperature is between 110 to 150 F, carbon-to-nitrogen ratio is 

20:1 to 40:1, moisture is 40% to 60%, and pH is 5.5 to 9.0. 

Points: Open Lot - 0 points; Freestall Scrape – 0 points; Freestall Flush – 0 points 

Compliance: None 

Management 

Considerations: Compost windrow should be have a pile height between 3 and 10 feet. Windrows 

less than 3 feet will not have sufficient insulation to maintain temperatures over 

100o

F. Windrows with heights greater than 10 feet have been shown to have higher 

risks of spontaneous combustion. 

Composting with Static Piles. 

Definition: Engineered composting system through the aerobic decomposition of manure or 

other organic materials placed in long rows that are not turned/mixed but have 

aeration pipes installed to facilitate increased air transfer. Bulking agents such as 

shredded wood should be used to ensure pile porosity. 
Scientific Basis for the Control of Ammonia 

from Dairy Farms Best Management Practices 7/18/06 

16

Points: Open Lot - 6 points; Freestall Scrape – 4.5 points; Freestall Flush – 3 points 

Compliance: Observation 

Management 

Considerations: Close management needs to be made when establishing static compost pile to 

ensure that all materials are thoroughly mixed and meet recommended guidelines. 

For optimum composting conditions the carbon to nitrogen ration (C:N) should be 

between 30 – 40:1, and the moisture content should be between 50 – 60% moisture. 

Adding supplemental carbon sources will also increase porosity within the compost 

pile allowing for better aeration within the pile. No special microbes are required for 

sufficient composting. For more information on static pile management, consult the 

“On-Farm Composting Handbook, NRAES-54”; call 607-255-7654 to order.

Force Aeration Composting. 

Definition: Engineered composting method using long rows or containers where air is drawn or 

forced into the piles using mechanical blowers. These piles are not turned. Make 

sure air is dispersed evenly through the pile. Bulking agents such as shredded wood 

should be used to ensure pile porosity. 

Points: Open Lot - 10 points; Freestall Scrape – 7.5 points; Freestall Flush – 5 points 

Compliance: Observation 

Management 

Considerations: Close management needs to be made when establishing compost pile, prior to 

aeration, to ensure that materials are thoroughly mixed and meet recommended 

guidelines. Systems can be aerated by either pushing air into the compost pile or 

pulling air through the pile (see practice: Force Aeration Composting with Biofilter). 

Additionally, producers should consider temperature control aeration systems to 

reduce operational cost. 

 For optimum composting conditions the carbon to nitrogen ration (C:N) should be 

between 30 – 40:1, and the moisture content should be between 50 – 60% moisture. 

Adding supplemental carbon sources will also increase porosity within the compost 

pile allowing for better aeration within the pile. No special microbes are required for 

sufficient composting. For more information on forced aeration, consult the “On-Farm 

Composting Handbook, NRAES-54”; call 607-255-7654 to order.

Force Aeration Composting with Biofilter. 

Definition: Engineered composting method using long rows or containers of carbon material 

where air is drawn through the compost and discharged into a biofilter. These piles 

are not turned. Bulking agents such as shredded wood should be used to ensure 

pile porosity. 

Points: Open Lot - 12 points; Freestall Scrape – 8 points; Freestall Flush – 6 points 

Compliance: Observation 

Management 

Considerations: This specialized method of force aeration composting, pulls air through a compost 

pile and discharges air into a biofilter. Biofilter is comprised of half compost and half 

shredded wood by volume and a sprinkler system to maintain between 40 – 50% 

moisture within the biofilter. This practices works through filtering volatile compounds 

and ammonia and then allowing aerobic microorganisms to degrade the compounds. 
Scientific Basis for the Control of Ammonia 

from Dairy Farms Best Management Practices 7/18/06 

17

 Close management needs to be made when establishing compost pile, prior to 

aeration, to ensure that materials are thoroughly mixed and meet recommended 

guidelines. Producers should consider temperature control aeration systems to 

reduce operational cost. 

 For optimum composting conditions the carbon to nitrogen ration (C:N) should be 

between 30 – 40:1, and the moisture content should be between 50 – 60% moisture. 

Adding supplemental carbon sources will also increase porosity within the compost 

pile allowing for better aeration within the pile. No special microbes are required for 

sufficient composting. For more information on forced aeration, consult the “On-Farm 

Composting Handbook, NRAES-54”; call 607-255-7654 to order.

LAND APPLICATION PRACTICES

Soil Injection – Slurry. 

Definition: Placement of manure slurry (manure of 8-15% solids) or separated solids beneath 

the soil surface with a minimum of mixing or stirring of the soil. Rate of slurry is not to 

exceed the Nutrient Management Plan recommendation for the actively growing crop. 

Points: Open Lot - 10 points; Freestall Scrape – 15 points; Freestall Flush – 7.5 points 

Compliance: Recordkeeping 

Management 

Considerations: Injection on slurry or separated solids will reduce ammonia emissions, odor, and the 

potential of flies. The nitrogen value of the slurry will be 15 – 40% than if the manure 

was not incorporated. Producers should consult their nutrient management planner 

to review the effect of decreased ammonia loss on agronomic performance. 

Incorporation of Manure within 24 Hours. 

Definition: Tilling of field surface following liquid or solid manure application within 24 hours from 

the time the application of the manure begins. Also effective in reducing hydrogen 

sulfide emissions and fly propagation. 

Points: Open Lot - 10 points; Freestall Scrape – 10 points; Freestall Flush – 10 points 

Compliance: Recordkeeping – documented twice: application and incorporation dates

Management 

Considerations: Incorporation of manure will reduce ammonia emissions, odor, and the potential of 

flies. The nitrogen value of the slurry will be 15 – 40% than if the manure was not 

incorporated. Producers should consult their nutrient management planner to review 

the effect of decreased ammonia loss on agronomic performance. 

Incorporation of Manure within 48 Hours. 

Definition: Tilling of field surface following liquid or solid manure application within 48 hours from 

the time the application of the manure begins. Also effective in reducing hydrogen 

sulfide emissions and fly propagation. 

Points: Open Lot - 5 points; Freestall Scrape – 5 points; Freestall Flush – 5 points 

Compliance: Recordkeeping – documented twice: application and incorporation dates 

Management 
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Considerations: Incorporation of manure will reduce ammonia emissions, odor, and the potential of 

flies. The nitrogen value of the slurry will be 15 – 40% than if the manure was not 

incorporated. Producers should consult their nutrient management planner to review 

the effect of decreased ammonia loss on agronomic performance. 

Nitrification of Lagoon Effluent. 

Definition: Use of an engineered aeration system, typically fixed media, to convert stored 

wastewater ammonia to nitrate prior to irrigation. Also effective in reducing volatile 

organic compounds, biological oxygen demand, and odor during application. 

Points: Open Lot - 10 points; Freestall Scrape – 10 points; Freestall Flush – 15 points 

Compliance: Deviation Log 

Management 

Considerations: Similar to fixed media aeration system, however, effluent is nitrified (ammonia 

converted to nitrate) prior to application. This practice will not prevent losses of 

ammonia that occur during storage, but will conserve the nitrogen that is typically lost 

during and immediately following irrigation. Operational cost for fixed media aeration 

systems are moderate compared to other aeration systems. Several systems have 

been shown to achieve an environmentally friendly reduction of nitrogen while 

reducing odor potential of treated wastewater.

Low Pressure & Energy Application Systems (LEPA). 

Definition: Center pivot and liner-move irrigation strategy that applies liquids at low pressures 

using drop nozzles. Larger droplets result in lower emissions but may cause 

infiltration problems on some soils. Designed systems and sprinkler packages 

should not exceed 35 psi. Low pressure overhead sprinklers and wheel lines do not 

qualify as LEPA technologies. Also effective on hydrogen sulfide and odor. 

Points: Open Lot - 7 points; Freestall Scrape – 7 points; Freestall Flush – 10 points 

Compliance: Observation 

Management 

Considerations: Producers should consult with Certified Irrigation Designer (CID) and Nutrient 

Management Planner before converting non-LEPA pivots and linear move systems. 

Practice is not recommended on highly erodable land (HEL).

Freshwater Dilution. 

Definition: Dilute irrigated wastewater by a minimum of 50% (1:1 ratio waste to fresh water) 

during all irrigation events. Dilutions can be made in approved mixing pond or 

chemigation systems. 

Points: Open Lot - 5 points; Freestall Scrape – 8 points; Freestall Flush – 8 points 

Compliance: Observation or Recordkeeping: Determined by system design 

Management 

Considerations: Regardless of dilution rate, producers still need to take precautions of applying 

wastewater to crops close to harvest, especially those that will be used for direct 

human consumption. 
Scientific Basis for the Control of Ammonia 

from Dairy Farms Best Management Practices 7/18/06 

19

Pivot Drag Hoses. 

Definition: Low pressure application method that allows the liquid to be applied on the soil 

surface directly in the row. This method decreases the amount of liquid lost to wind 

drift, and to decrease the energy costs associated with pumping enough liquid to 

maintain the high pressures required for the impact heads. Systems should use 

pressure regulators or ball valves to regulate flow from drag hoses. Also effective on 

hydrogen sulfide and odor. 

Points: Open Lot - 8 points; Freestall Scrape – 8 points; Freestall Flush – 10 points 

Compliance: Observation 

Management 

Considerations: Pressure regulators or valves should be used on each drop to manage flow rates 

from drag hose. Producers should consult with Certified Irrigation Designer (CID) 

and Nutrient Management Planner before converting non-drag hose pivots and linear 

move systems. Practice is not recommended on highly erodable land (HEL) or fields 

with little or no ground cover. 

Subsurface Irrigation. 

Definition: Specialized irrigation method that allows for precise applications of liquid to the root 

zone of the plant. System requires specialized filtering system to handle wastewater 

solids and specialized "wastewater approved" drip lines should be used to prevent 

clogging. Also effective on hydrogen sulfide and odor. 

Points: Open Lot - 10 points; Freestall Scrape – 10 points; Freestall Flush – 12 points 

Compliance: Observation 

Management 

Considerations: In addition to using wastewater approved drip lines, special attention should be taken 

in the selection of filter media and selecting backwash frequencies. For more 

information on wastewater subsurface drip systems visit: www.oznet.ksu.edu/sdi/ 

 The nitrogen value of the slurry will be 15 – 40% than if the manure was not 

incorporated. Producers should consult their nutrient management planner to review 

the effect of decreased ammonia loss on agronomic performance.