Models & Tools to Improve Manure Management: Part II

This webinar features the Oregon NMPT, an internet-based record keeping and planning tool, and the Ruminant Farm Systems (RuFaS) project, which aims to build an integrated, whole-farm model that simulates milk, meat, and crop production, and critical metrics of sustainability from ruminant farms. This presentation was originally broadcast on October 20, 2023. Continue reading “Models & Tools to Improve Manure Management: Part II”

Implications of Manure Additives: Both Purposeful and Accidental

This webinar discusses purposeful additives like nitrification inhibitors and biochar as well as accidental additives like copper sulfate from disinfecting foot baths and how these things can and should impact our decisions when applying manure. This presentation was originally broadcast on September 22, 2023. Continue reading “Implications of Manure Additives: Both Purposeful and Accidental”

Environmental Benefits of Manure Application

For centuries, animal manure has been recognized as a soil “builder” because of its contributions to improving soil quality. Environmental benefits are possible from manure application if manure and manure nutrients are applied and timing and placement follows best management practices. When compared to more conventional fertilizer, manure properly applied to land has the potential to provide environmental benefits including:

    • Increased soil carbon and reduced atmospheric carbon levels
    • Reduced soil erosion and runoff
    • Reduced nitrate leaching
    • Reduced energy demands for natural gas-intensive nitrogen(N) fertilizers

Manure Effects on Soil Organic Matter

Manure contains most elements required for plant growth including N, P, potassium, and micronutrients (Manure as a Source of Crop Nutrients and Soil Amendment). However, it is manure’s organic carbon that provides its potential environmental value. Soil organic matter is considered nature’s signature of a productive soil. Organic carbon from manure provides the energy source for the active, healthy soil microbial environment that both stabilizes nutrient sources and makes those nutrients available to crops.

photo of solid manure spreader
Manure is comparable to commercial fertilizer as a plant food and, if applied according to a sound nutrient plan, has environmental benefits over commercial fertilizer. cc2.5 manure nutrient management group

Several long-term manure application studies have illustrated its ability to slow or reverse declining soil organic levels of cropland:


    The ability of manure to maintain or build soil organic matter levels has a direct impact on enhancing the amount of carbon sequestration in cropped soils.Manure organic matter contributes to improved soil structure, resulting in improved water infiltration and greater water-holding capacity leading to decreased crop water stress, soil erosion, and increased nutrient retention. An extensive literature review of historical soil conservation experiment station data from 70 plot years at 7 locations around the United States suggested that manure produced substantial reductions in soil erosion (13%-77%) and runoff (1%-68%). Increased manure application rates produced greater reductions in soil erosion and runoff. Additional studies during years following manure application suggest a residual benefit of past manure application.

    Overview of Manure Impacts on Soil (Mark Risse, University of Georgia). Visit the archived webinar for additional videos on carbon, fertility, and soil health.

    Manure Effects on Soil Erosion

    In addition, surface application of manure behaves similarly to crop residue. Crop residue significantly decreases soil erosion by reducing raindrop impact which detaches soil particles and allows them to move offsite with water runoff. Data has been published showing how manure can coat the soil surface and reduce raindrop impact in the same way as crop residue. Therefore, in the short-term, surface manure applications have the ability to decrease soil erosion leading to a positive impact on environmental protection.

    Organic Nitrogen

    In addition, organic N (manure N tied to organic compounds) is more stable than N applied as commercial fertilizer. A significant fraction of manure N is stored in an organic form that is slowly released as soils warm and as crops require N. Commercial fertilizer N is applied as either nitrate or an ammonium (easily converted to nitrate). Nitrate-N is soluble in water and mobile. These forms contribute to leaching during excess precipitation (e.g., spring rains prior to or early in growing season) or irrigation. Manure N’s slow transformation to nitrate is better timed to crop N needs, resulting in less leaching potential. In fact, manure N is a natural slow-release form of N.

    Energy Benefits

    Recycling of manure nutrients in a cropping system as opposed to manufacturing or mining of a new nutrient resource also provides energy benefits. Commercial nitrogen fertilizers consume significant energy as a feedstock and for processing resulting in greenhouse gas emissions. Anhydrous ammonia requires the equivalent of 3300 cubic feet of natural gas to supply the nitrogen requirements of an acre of corn (assuming 200 lb of N application). Phosphorus and potassium fertilizers also have energy requirements for mining and processing. Substituting manure for commercial fertilizers significantly reduces crop production energy costs

    It is important to remember that the environmental benefits of manure outlined in this article are only beneficial when best management practices for reducing soil erosion are implemented in concert with proper levels of manure nutrient application and use.

    Recommended Reading on Environmental Benefits of Manure


  • Authors: Rick Koelsch, University of Nebraska, and Ron Wiederholt, North Dakota State University
  • Reviewers: Charles Wortmann, University of Nebraska, and Steve Brinkman, Iowa NRCS
    Last reviewed on October 25, 2022 by Leslie Johnson, Animal Manure Management Extension Educator, Nebraska Extension.

The Manure Analysis Proficiency Program: Trends in laboratory manure testing methods


The Manure Analysis Proficiency (MAP) Program, administered by the Minnesota Department of Agriculture, began in the mid-1990s to assist US Midwest analytical laboratories to verify the accuracy (including both bias and precision) of laboratory manure analyses. In 2003, the program expanded nationally and continues today. With an annual enrollment of 60 to 74 labs each year over the past two decades and the analysis of 120 manure proficiency samples of 12 test parameters, trends in laboratory methods and performance have arisen. The presentation will cover inter-laboratory bias and precision of the primary manure analysis parameters: total solid content, nitrogen, ammonia nitrogen (NH3-N), phosphorus and potassium.

What Did We Do?

The MAP Program was designed to follow international standards under the ISO/IEC 17025 general requirements for the coordination of a proficiency testing program. This includes development and use of standard protocols for the preparation of manure proficiency testing (PT) samples, the use of blind sample replicates for the assessment of intra-lab precision, and the implementation of robust statistical measures for the assessment of data for the evaluation of both laboratory accuracy (bias) and precision.

Since 2002, the MAP program has sent PT samples to laboratories twice per year. Each cycle includes three manure types with each type having three replicates (for a total of nine manure samples). The PT samples are selected based on source animal type and a range of total solids (2-90%). Samples are thoroughly ground and homogenized and then packaged and frozen prior to overnight shipping to program participants. Each participating laboratory completes the required tests and sends back their results along with their analytical methods used to the MAP program. With the results tabulated from all laboratories each cycle, method bias is assessed based on the inter-lab (or between lab) median and 95% confidence limits (using the median absolute deviation). Precision is assessed based on the intra-lab (or within lab) relative standard deviation of PT sample replicates. Participating labs are provided graphical reports illustrating method performance as well as lab bias and precision.

One-hundred twenty-nine manure PT samples from dairy, beef, swine, and poultry operations have been evaluated since 2002 and each sample was analyzed by 60 to 74 labs participating in the MAP program (depending on the year). The samples ranged from 3.1 to 91% total solids, 0.02 to 2.71% total nitrogen, and 0.05 to 0.48% total phosphorus. With this wide range of manure types and conditions, plus the ability to pair data with manure analysis methods and accuracy ratings, we can evaluate the efficacy of certain methods and discuss their pros and cons.

What Have We Learned?

MAP program results for nitrogen have shown the dry combustion method to be unsuitable for manure samples with total solid content less than 10%. Results for four different ammonia methods indicate generally good agreement between methods in the median concentrations, but methods varied in precision. Across samples, intra-laboratory precision decreased with decreasing analyte concentration, often associated with decreased manure total solid content. In general, total solids, phosphorus and potassium methods were of high precision with intra-lab precision < 5%. Manure test parameters exhibiting poor intra-lab precision were EC, pH, and NO3-N.

Future Plans

The MAP program continues to operate under the Minnesota Department of Agriculture in partnership with Central Lakes College in Brainerd, MN. The team is currently working with the USDA-NRCS (who provided funding), the University of Minnesota, and laboratory directors of public and private laboratories to update the “Recommended Methods of Manure Analysis” manual which is expected to be released and printed in 2022.


Robert Miller, Technical Director, Agricultural Laboratory Proficiency Program

Corresponding author email address

Additional author

Jerry Floren, MAP Program Director (retired), Minnesota Department of Agriculture

Additional Information


Larry Gunderson at the Minnesota Department of Agriculture


The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Ammonia Loss Following Application of Swine Manure


The amount of nitrogen lost to the air as ammonia following the application of manure is important for two reasons. From the farmer’s point of view, the loss of nitrogen as ammonia gas represents a loss of fertilizer that could have contributed to the production of a crop. From an environmental point of view, ammonia lost from a field to the atmosphere is a source of air pollution that can combine with sulfites and nitrates in the atmosphere to form extremely fine particulate matter (PM2.5) that can have harmful effects on human health and can contribute to water pollution when deposited into surface water by rainfall. Land application of animal manure is one of many sources of ammonia emissions that also include municipal and industrial waste treatment, use and manufacture of fertilizers, combustion of fossil fuel, coke plants and refrigeration (USEPA, 1995).

Animal manure can be used as a fertilizer substitute. However, the types of nitrogen in manure are more complicated than those found in most common chemical fertilizers. Nitrogen can be present in manure as ammonium-N, ammonia-N, organic-N, and nitrate-N. Not all the nitrogen in manure is immediately available for plant use. Most animal manure contains very little nitrate-N and as a result it is typically not measured. However, manure that receives aerobic treatment, i.e., composting or aeration, should be analyzed for nitrate-N since it is a valuable form of nitrogen that is the same as contained in one of the most common types of fertilizer – ammonium nitrate.

Most laboratories measure the total ammoniacal nitrogen content (TAN) of animal manure, which includes ammonium-N and ammonia-N (TAN = NH4+-N + NH3 -N). The amount of TAN that is in the ammonia form depends greatly on the pH of the manure. At a pH of 6.5 none of the TAN is in the ammonia form – it is all ammonium-N which is a great form of plant fertilizer.  At a high pH, such as, 9.5, 65% of the TAN is in the ammonia form. Most animal manures have a pH in the range of 8 to 8.5 and about 10% most of the TAN is ammonia-N and can be lost to the air. As a result, TAN is often labeled as ammonium-N on manure analysis reports.

A key aspect of using animal manure as a fertilizer substitute is to make a good estimate of the fraction of the total nitrogen contained in the animal manure that can be used to grow a plant. This portion of the nitrogen is called the plant available nitrogen (PAN) and can be estimated using the following equation:

PAN =mf Organic-N + Af TAN + Nitrate-N. (1)

Most of the nitrogen in untreated slurry and solid animal manure is organic nitrogen (organic-N) that must be mineralized in the soil to become available to plants as ammonium-N. The fraction of the organic-N that will be mineralized during the growing season is represented in equation 1 as the mineralization factor, mf. The value of the mineralization factor varies depending on animal species, the amount of treatment, as well as soil pH, moisture, and temperature. The values of mf recommended are 0.70 for lagoon water and 0.50 for swine slurry (Chastain, 2006).

The fraction of TAN in manure that will be available to the plant is represented by the ammonium-N availability factor, Af. The ammonium-N availability factor (a decimal) is determined from the fraction of TAN lost to the air as ammonia-N using the following formula:

Af =1-( AL/ 100). (2)

The amount of ammonia-N lost following application varies with the method of application, the extent and timing of incorporation in the soil by disking as well as the pH of the manure, the pH that the manure attains following application, and the air temperature. Most extension publications provide recommended values for estimating ammonia-N losses. For example, Clemson Cooperative Extension (CAMM, 2005) recommends use of an ammonia loss (AL) of 50% for broadcast of manure without incorporation. This would mean that a value of 0.5 is used for ammonium-N availability factor (Af) in equation 1. If the manure is incorporated into the soil within one day the recommended value for AL is 20% giving an Af value of 0.80.

The amount of nitrate-N contained in animal manure is often so small that it is not measured. However, manure that is exposed to enough air or that is treated aerobically will have a significant amount and measurement of the nitrate-N content is recommended. All the nitrate-N contained in manure is 100% plant available.

Various studies and reviews (Chastain, et al., 2001; Montes, 2002; Montes and Chastain, 2003; Chastain, 2006) have indicated that the amount of ammonia lost following application of animal manure varies much more than indicated by most extension recommendations (e.g., CAMM, 2005). The result of large differences between recommended estimates and actual values is either substantial over or under estimation of the amount of ammonia emissions to the air as well as over or underestimation of the amount of nitrogen that will be available for the plant. The objective of this paper is to provide practical recommendations for the ammonium-N availability factors for swine manure based on the application method, total solids content, and the time between broadcast and incorporation.

What Did We Do?

The data and the correlations used to develop the recommendations in this paper were provided by Montes (2002) and Chastain (2006).  The effect of the application method on ammonia-N loss was estimated using the following equation:

AL =fA ALBC. (3)

The application factors, fA, that correspond to an application method are given in Table 1 and ALBC was the ammonia loss for broadcast manure. The value of the ammonium-N availability factor, Af, for each application method was calculated using the definition given previously in equation 2.

How fast ammonia is lost following broadcast application of manure was determined by Montes (2002). The results indicated that ammonia-N loss following irrigation of lagoon water occurred too quickly to consider incorporation by disking. Values for broadcast and incorporation for slurry manure are given in Table 1. The results indicated that incorporation must follow broadcast of slurry manure within 8 hours if it is desired to reduce ammonia-N loss by 50% (fA=0.50).


Table 1. Application method factors to describe the reduction in ammonia loss as compared to broadcast application of manure. (Values based on reviews of the literature by Chastain et al., 2001 and Montes, 2002).
Application Method fA What type of manure can use this method?
Broadcast without incorporation 1.0 All
Broadcast followed by incorporation within 4 hoursA 0.29 Slurry
Broadcast followed by incorporation within 6 hoursA 0.40 Slurry
Broadcast followed by incorporation within 8 hoursA 0.50 Slurry
Broadcast followed by incorporation within 12 hoursA 0.64 Slurry
Band spreading (drop or trailing hose) 0.50 Liquid and Slurry
Band spreading with immediate shallow soil cover 0.12 Liquid and Slurry
Shallow injection (2 to  inches below soil surface) 0.10 Liquid and Slurry
Deep injection (4 to 6 inches below soil surface) 0.08 Liquid and Slurry
AfA calculated using K = 0.086 h-1 (Chastain, 2006)

A few studies indicated that application of manure to bare soil versus cut hay, or plant residue reduced ammonia-N loss following broadcast by 10% to 20% (see Montes, 2002 and Chastain, 2006). However, it was decided that there was not sufficient data to generalize the result for practical use.

What Have We Learned?

The model was applied to as wide a range of swine manure application situations as possible. The results were tabulated as ammonium-N availability factors, Af, that may be used in the PAN equation (equation 1) along with an estimate for the mineralization factor.

Variation in Ammonium-N Availability by Application Method

The impact of application method on the ammonium-N availability factor for swine manure is shown in Table 2. Application method had the least impact on irrigation of surface water from an anaerobic treatment lagoon. The value of Af was 0.98 for irrigated swine lagoon water. This corresponded to an ammonia-N loss of 2% (AL = (1-Af) x 100). The amount of ammonia-N lost was low since more than 0.25 inches of lagoon water was applied, and most of the ammonium-N was washed into the soil. However, the ammonium-N availability factors for broadcast of manure decreased sharply as the total solids content of swine manure increased. This corresponded to ammonia-N loss ranging from 8% for liquid manure (TS = 1% to 4%) to 58% for thick slurry (TS = 15% to 20%). It can also be seen in the table that all the ammonium-N conserving application methods increased in effectiveness as the TS content of swine manure increased.


Table 2. Variation in ammonium nitrogen availability factors, Af, for swine manure and treatment lagoon surface water based on application method. (AL = (1 – Af) x 100)
Description Broadcast or Large Bore Irrigation Broadcast followed by incorporation within 6 hours Band Spreading Band Spreading with Shallow Cover Shallow Injection Deep Injection
Lagoon Surface WaterA 0.98 NA 0.99 1.00 1.00 1.00
Liquid or SlurryB
TS=1% to 4% 0.92 0.97 0.96 0.99 0.99 0.99
TS=5% to 6% 0.82 0.93 0.91 0.98 0.98 0.99
TS=7% to 8% 0.75 0.90 0.88 0.97 0.98 0.98
TS=9% to 12% 0.66 0.86 0.83 0.96 0.97 0.97
TS=13% to 14% 0.56 0.82 0.78 0.95 0.96 0.96
TS=15% to 20% 0.42 0.77 0.71 0.93 0.94 0.95
AALBC = 14.30 TS – 4.75, R2 = 0.791, TS = 0.5%, Chastain (2006)
BALBC = 23.284 TS, R2 = 0.875, Chastain (2006)

Comparison of the Use of New Ammonium-N Availability Factors and Current Clemson Extension Recommendations for Broadcast Application of Swine Manure

Selection of the ammonium-N availability factor (Af) and mineralization factor (mf) for a manure type and application method has a large effect on the accuracy of the estimate of nitrogen that can be used to fertilize a crop as well as the estimate of ammonia-N lost to the air. The PAN estimate determines the amount of manure applied per acre (gal/ac) and the amount of P2O5 and K2O that are applied (lb/ac). The impact of using constant values of Af and mf that are different from values that more closely match the data was studied by comparing the results for spreading lagoon water (TS = 0.5%) and slurry (TS = 7.5%) to meet a target application rate of 100 lb PAN/ac. The results are provided in Table 3. The impact of settling and biological treatment in the lagoon was indicated by the low TS content (TS=0.5%) and the fact that the lagoon water contained two pounds of TAN for every pound of organic-N. Swine slurry (TS = 7.5%) contained 1.2 pounds of TAN per pound of organic-N.

Comparison of the estimates using Clemson Extensions current recommendations with the results provided in this paper led to the following observations.

    • Using the new Af and mf values that varied by manure type (lagoon water vs slurry) provided higher PAN estimates than the Clemson Extension recommendations.
    • The higher PAN estimates resulted in reductions in the amount of manure needed to provide 100 lb PAN/ac.
    • The amount of ammonia-N lost per acre per 100 lb PAN applied was much lower using the new factors for estimating PAN as compared to using Clemson Extension values for lagoon water and swine slurry. Using Clemson Extension values over-estimated the ammonia-N loss/ac by 133% to 1133%.
    • The inaccuracies in PAN estimates for lagoon water and slurry manure also impacted plant nutrient application rates. Using the PAN estimates based on Clemson Extension recommendations to determine manure application rates resulted in over application of nitrogen by 17% to 21%. Similar over-applications were observed for P2O5 and K2 Therefore, better estimates of PAN can help to reduce excessive applications of phosphorous and provide better estimates of potash (K2O) application rates.
    • Comparison of the estimates of the ammonia-N lost per acre following broadcast of manure for the examples shown in Table 4 demonstrates the need to consider using values of Af and mf that more closely agree with the available data.
    • It must be emphasized that slurry manure with a higher TS content than 7.5% and heavily bedded manure were not included in the examples in this paper. The ammonia-N loss values will be higher and must be calculated using the Af values provided in this paper along with the corresponding manure analysis to yield valid conclusions.

Impact of Selected Ammonium-N Conserving Application Methods on Ammonia-N Loss per Acre, and P2O5 Application Rate

The impact of application method on the estimates of PAN, ammonia-N loss, and phosphorous application rates was calculated for swine slurry using the tabulated values for the ammonium-N availability factors given in Table 2.  Lagoon water was not included because irrigation is the most common and cost-effective method of application, and the amount of ammonia-N lost to the air was the least. The application methods that were compared were broadcast, broadcast followed by incorporation within 6 hours, band spreading, band spreading with shallow soil cover, and shallow injection. Results for deep injection were not included because the improvements were very small compared with shallow injection (see Table 2). Furthermore, the horsepower and fuel costs of deep injection are higher than for shallow injection. The results are given in Table 4.

The results indicated that broadcast with incorporation within 6 hours provided a reduction in ammonia-N loss per acre of 65% and a reduction in the P2O5 application rate of 11%. Band spreading provided almost the same benefits (57% reduction in ammonia-N loss and 10% reduction in lb P2O5/ac) but would be achieved with only one pass across a field. Adding a method to immediately cover a band of manure with soil provided reductions in ammonia-N loss of 90% and reduction of the P2O5 application rate by 16%. Shallow injection provided a modest improvement in ammonia-N emissions (93%) as compared to band spreading with shallow cover. Shallow injection also provided about the same benefit in reduction of phosphorous application rate as band spreading with shallow cover.


Table 3. Comparison of land application rate and ammonia-N loss estimates using tabulated model results and current Clemson University Extension recommendations for broadcast application of swine lagoon surface water and slurry manure. Target nutrient application rate = 100 lb PAN/ac.
Lagoon Water Slurry
TS, % 0.5 7.5
TAN, lb/1000 gal 4.3 23.0
Org-N, lb/1000 gal 2.0 19.0
P2O5, lb/1000 gal 3.6 33.0
K2O, lb/1000 gal 7.9 28.0
Land Application Rates and Ammonia-N Loss Estimates Using Clemson Extension Recommendations
Mineralization factor, mf 0.60 0.60
Ammonium-N availability factor, Af 0.80 0.50
PAN estimate, lb PAN/1000 gal 4.6 22.9
Application rate to provide 100 lb PAN/ac, gal/ac 21,552 4,367
Resulting application rate for P2O5, lb/ac 78 144
Resulting application rate for K2O 170 122
Ammonia-N Loss, lb per acre / 100 lb PAN 18.5 50.2
Land Application Rates and Ammonia-N Loss Estimates Using New Recommendations
Mineralization factor, mf 0.70 0.50
Ammonium-N availability factor, Af 0.98 0.75
PAN estimate, lb PAN/1000 gal 5.6 26.8
Application rate to provide 100 lb PAN/ac, gal/ac 17,813 3,738
Resulting application rate for P2O5, lb/ac 64 123
Resulting application rate for K2O 141 105
Ammonia-N Loss, lb per acre / 100 lb PAN 1.5 21.5
Key Impacts of Inaccurate Estimates of Af, and PAN
Over-estimation of Ammonia-N Loss/ac 1133% 133%
Actual PAN Application Rates Using Clemson Extension Recommendations to Determine Manure Application Rate, lb PAN/ac and percent over-application of PAN (%) 121
Difference in Application of P2O5, lb/ac (%) 14
Difference in Application of K2O, lb/ac (%) 29


Table 4. Impact of Application Method on Ammonia-N Loss and P2O5 Application Rate for Swine Slurry. The total solids and plant nutrient contents were given previously in Table 3 and the mineralization factor was 0.50 for all application methods.
Slurry, TS = 7.5%
Broadcast – no incorporation
Mineralization factor, mf 0.50
Ammonium-N availability factor, Af 0.75
PAN estimate, lb PAN/1000 gal 26.8
Application rate to provide 100 lb PAN/ac, gal /ac 3,738
Resulting application rate for P2O5, lb/ac 123
Ammonia-N Loss, lb per acre / 100 lb PAN 21.5
Broadcast – incorporation within 6 hours
Ammonium-N availability factor, Af 0.90
PAN estimate, lb PAN/1000 gal 30.2
Application rate to provide 100 lb PAN/ac, gal /ac 3,311
Resulting application rate for P2O5, lb/ac 109
Ammonia-N Loss, lb per acre / 100 lb PAN 7.6
Reduction in Ammonia-N loss Compared to Broadcast 65%
Reduction in P2O5 Application Rate 11%
Band Spreading
Ammonium-N availability factor, Af 0.88
PAN estimate, lb PAN/1000 gal 29.7
Application rate to provide 100 lb PAN/ac, gal /ac 3,362
Resulting application rate for P2O5, lb/ac 111
Ammonia-N Loss, lb per acre / 100 lb PAN 9.3
Reduction in Ammonia-N loss Compared to Broadcast 57%
Reduction in P2O5 Application Rate 10%
Band Spreading with Shallow Cover
Ammonium-N availability factor, Af 0.97
PAN estimate, lb PAN/1000 gal 31.8
Application rate to provide 100 lb PAN/ac, gal /ac 3,144
Resulting application rate for P2O5, lb/ac 104
Ammonia-N Loss, lb per acre / 100 lb PAN 2.2
Reduction in Ammonia-N loss Compared to Broadcast 90%
Reduction in P2O5 Application Rate 16%
Shallow Injection
Ammonium-N availability factor, Af 0.98
PAN estimate, lb PAN/1000 gal 32.0
Application rate to provide 100 lb PAN/ac, gal /ac 3,121
Resulting application rate for P2O5, lb/ac 103
Ammonia-N Loss, lb per acre / 100 lb PAN 1.4
Reduction in Ammonia-N loss Compared to Broadcast 93%
Reduction in P2O5 Application Rate 17%

Future Plans

The model results provided in this paper are currently being used to develop extension programs and will be used to update extension publications and recommendations for producers. It is hoped that these tabulated ammonium-N availability factors will be used to increase the precision of using swine manure as a fertilizer substitute and making better estimates of ammonia-N emissions.


John P. Chastain, Professor and Extension Agricultural Engineer, Agricultural Sciences Department, Clemson University

Corresponding author email address

Additional Information

CAMM. 2005. Confined Animal Manure Managers Program Manual – Swine Version. Clemson, SC.: Clemson University Extension. Available at

Chastain, J.P. 2006. A Model to Estimate Ammonia Loss Following Application of Animal Manure, ASABE Paper No. 064053. St. Joseph, Mich.: ASABE.

Chastain, J. P., J. J. Camberato, and J. E. Albrecht. 2001. Nutrient Content of Livestock and Poultry Manure. Clemson, SC.: Clemson University.

Montes, F. 2002. Ammonia volatilization resulting from application of liquid swine manure and turkey litter in commercial pine plantations. MS Thesis, Clemson, SC.: Clemson University.

Montes, F., and J.P. Chastain. 2003. Ammonia Volatilization Losses Following Irrigation of Liquid Swine Manure in Commercial Pine Plantations. In Animal, Agricultural and Food Processing Wastes IX: Proceedings of the Nineth International Symposium, 620-628. R.T. Burnes, ed. St. Joseph, Mich.: ASABE.

USEPA. 1995. Control and Pollution Prevention Options for Ammonia Emissions (EPA-456/R-95-002), report prepared by J. Phillips, U.S. Environmental Protection Agency, Control Technology Center. Research Triangle Park, NC. Available at


The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Merits of Manure Content Library


The right amount of animal manure in the right location can benefit crops, soil, and water resources.  However, too much manure or manure in the wrong place is an environmental concern.  A recent survey of attitudes from farmers and their advisors on the benefits and barriers for manure use indicates that there is widespread knowledge of manure value for cropping systems, but logistical and community barriers remain. The survey also found that all respondents rated peer-to-peer interactions as the most influential on their decision-making for these topics. Thus, more extension efforts should be focused in assisting AFO managers and advisors to communicate messages on the value of manure and strategies for overcoming barriers, among their specific networks. For example, knowledge of the relationship of manure and soil health benefits is low among some segments. Farmers and their advisors all have very low opinions and understanding of manure’s benefits to environmental quality. Helping farmers, educators, and advisors articulate among themselves and to their rural communities the water quality benefits of organic fertilizers when applied to only meet agronomic needs of the crop may need expanded investments. With these needs in mind a team from the Universities of Nebraska, Minnesota, and Iowa State, and the assistance of the North Central Region Sustainable Agricultural Research and Education program developed a library to provide educators and advisors with access to recommended resources that will assist in the discussion of manure’s benefits and challenges.

What Did We Do?

Consultation among the team identified the following categories of interest for readily accessible educational or outreach materials for manure impacts on:

    1. Soil health and soil quality
    2. Economics of production and yield
    3. Crop fertility
    4. Water quality
    5. On-farm research

And guidance to navigating barriers such as:

    1. Direct costs associated with manure use
    2. Odor and other community issues
    3. Agronomic challenges (such as imbalance nutrients)
    4. Regulations
    5. Logistical issues of application
    6. Using manure in specialty systems (such as organic production)

With the categories for materials established, the team conducted an initial survey of extant educational and outreach materials via general internet searches and review of content available through the Livestock and Poultry Environmental Learning Community. The types of content thus assembled were varied: social media content, video, summaries of research, published extension and scientific journal articles, websites, and other content such as podcasts and decision support tools. All were included since it was intended that these resources be helpful for educators, producers, or others to converse with their own networks easily and confidently on the manure topics identified. The team anticipated that users could use the library to expand their social media activity, and thus their communication networks, or to prepare more confidently to discuss manure via a local radio presentation or discussion with a county board. Or even to add an article to local print media or a blog or personal website. All items included in the library were free to repurpose (with attribution) in local outlets or personal sites.

After consultation, the library was built using Airtable ™, a platform to create low-code databases, tools, or other apps. This platform allows the team to internally build a flexible database of content which can be sorted easily into pre-set categories (for example, topics of specific seasonal relevant), and arrange content into easily perused views to improve the user experience on a platform that could be easily embedded into existing team sites, such as (Figure 1).

Figure 1. The user interface for the merits of manure library, several such sorted views are embedded on the LPELC website for audience exploration by topic, media type, or seasonal relevance. Within each view individual entries can be further searched or sorted to further narrow exploration.

Each entry (Figure 2) in the library has an individual entry card, which includes keywords and text descriptions to improve searchability as well as a downloadable file, or links to the resource where appropriate, and a short example of how this material could be shared in the user’s social media network (recommended twitter text). The team intended to provide library users with not only the educational content, but also the means to improve their own in-network communication on manure topics. Accordingly, when posting to social media, hashtags, mentions and links to other content help (a) reach users who are following a specific topic (e.g., #manure), (b) recognize someone related to the post (e.g., @TheManureLady) and (c) direct users to more content related to the graphic (e.g., URL to online article). For our content library, each item is accompanied by recommended text that can be copied and pasted into the post of a social media engine if desired.

Figure 2. A single-entry page for the library.

What Have We Learned?

Since its launch in 2021 the library has had 343 unique users, average time that each user spends interacting with the library is 129 seconds, a solid interaction time for a website – industry standard is 120-180 seconds. However, we do not have any measure for how time spent on the library page is transformed into use of the library content. It is evident that more work is needed to improve awareness of the tool among audiences of interest. To this end, the team decided to develop a recognizable brand for library materials which might help other potential users to find their way to the site (Figure 3).

Figure 3. Library logo.

Future Plans

Library administrators continue to look for ways to improve the library content, user experience, and awareness of the tool among potential users. An overview of content, accessibility, re-purposing, and submission of relevant material will be shared to publicize the resource, encourage utilization of available materials, and invite submissions of new content relevant to the manure management community.


Amy Schmidt, Associate Professor, University of Nebraska

Corresponding author email address

Additional authors

Leslie Johnson, Associate Extension Educator, Mara Zelt, Schmidt Lab Project Director, Amber Patterson, Schmidt Lab Media Communications Specialist, and Rick Koelsch, Professor Emeritus, University of Nebraska-Lincoln; Erin Cortus, Associate Professor, and Melissa Wilson, Assistant Professor, University of Minnesota; and Dan Andersen, Associate Professor, Iowa State University

Additional Information

The full library is accessible at


This product was assembled with financial assistance from the North Central Region Sustainable Agricultural Research and Education program.  NCR-SARE is one of four regional offices that run the USDA Sustainable Agriculture Research and Education (SARE) program, a nationwide grants and education program to advance sustainable innovation to American agriculture.