Manuresheds: Pennsylvania Case Study of Strategic Expansion of the Swine and Poultry Industries


The manureshed concept considers manure nutrients produced by livestock or poultry and the associated cropland which is needed to assimilate the nitrogen and phosphorus in that manure. An area of surplus manure nutrient production is considered a ‘source’ and the cropland that can accommodate the surplus is termed a ‘sink’. Manuresheds are managed on several scales from farm to county to regional levels. A large group of scientists, led by the USDA-ARS Long-Term Agroecosystem Research Network (LTAR), has explored the manureshed concept for all major animal industries of the US, while considering a wide array of aspects that influence manureshed characteristics and management.

Several manuscripts of the manureshed research team will be consolidated in a special edition of the Journal of Environmental Quality in 2022. Here we present findings from the manuscript focused on the swine industry (Meinen et al., 2022), which evaluates how interactions between manuresheds of different species occur in areas where species inventory overlap occurs. Although in the manuscript we explore dynamics in Iowa, North Carolina, and Pennsylvania, here we focus only on Pennsylvania’s interactions of drivers of expansion of the swine and poultry industries from the years 2000 to 2020. A diversity of factors influenced expansion and therefore the manureshed areas associated with these industries, including social, animal welfare, product quality, and nutrient management forces.

What Did We Do

We explored factors that influenced manureshed shifts for swine and poultry in Pennsylvania over two decades. Historical manureshed source counties for both industries were interconnected and located in the southeastern region of the state.

When siting a new on-farm animal housing facility for swine or poultry, integrators in Pennsylvania often consider the potential impact of odor before contracting with a farm. This places social considerations as a priority, and ahead of nutrient impact considerations in the siting protocol. Since 1999, the Pennsylvania State University has provided a no-cost Odor Site Evaluation Service for any proposed swine or poultry animal farm. The service uses maps, a site visit, and landscape characteristics to predict the potential for odor conflict with neighbors should a proposed animal housing facility be constructed. One swine integrator and one poultry integrator in particular utilized the service before signing contracts with landowners. A favorable Odor Site Evaluation report can assist with local permitting while a negative assessment may lead to site changes or the integrator not signing the contract for public image reasons. Locations of Odor Site Evaluations for swine and poultry were mapped over time at a county level for each industry, to demonstrate differences in locations in which each industry sought to expand (Figure 1). Over time, swine farm locations shifted north and west to where human populations and odor conflict potential were lower, while poultry siting locations remained near historic poultry locations. These north and west locations also coincide with manureshed sink counties where previous commercial swine operations were not historically located. Agricultural survey data (NASS, 2017) demonstrated that swine inventory (Figure 2) mirrored the trends in the Odor Site Evaluation data (Figure 1).

Figure 1. Location of Pennsylvania Odor Site Assessments for swine and poultry by county and over time. Maps show county-level locations of Pennsylvania Odor Site Assessments conducted for swine and poultry farms over five-year periods. The Odor Site Assessment evaluates potential odor conflict risk to neighbors from a proposed farm. From 1999 to 2020 the program assessed 254 swine sites (most for Country View Family Farms) and 275 poultry sites (most for Bell & Evans). Two assessments conducted in 1999 were moved to the year 2000 for graph continuity.


Figure 2: Locations of swine and poultry farms by county in Pennsylvania. Size of circle indicates animal units (1,000 lbs. of animals) of swine plus poultry based on county level inventory (NASS, 2017). Counties with less than 2,000 animal units of swine plus poultry did not receive an animal unit circle. Color represents relative contribution of each species to the total animal units.

What Have We Learned

Evaluation of the expansion of swine and poultry in Pennsylvania over the last 20 years demonstrates that the industries impact manuresheds differently. The swine industry has expanded west and north from historically dense swine manureshed source areas, while poultry industry expansion occurred close to its traditional home.

Contemporary expansion of facilities in the Pennsylvania swine industry is often driven by vertically integrated companies emphasizing animal health as a priority by seeking farm locations that are isolated from other swine facilities, to enhance efficiencies that high herd health status provides to production. Movement of the Pennsylvania swine industry to rural areas with lower densities of human populations assists with the industry’s objective to avoid odor conflict with neighbors, thus suggesting that social forces also shape manuresheds. Swine integrators seek producers that also farm nearby land that can accept manure, since the liquid nature of swine manure inhibits economics of transporting manure nutrients long distances in the current agri-food system. In turn, farmers that desire manure nutrients for cropping operations are expected to be better stewards of manure resources. The resulting impact on swine manuresheds is that expansion favors locally balanced manuresheds associated with each swine operation and shifts new manure sources into sink areas within the state.

Transportation distances to harvest facilities are very different for swine and poultry (Figure 3). A large driver of locating farms of a participating poultry integrator includes the desire to have broilers located within a 90-minute transport distance from the harvest facility to assure animal welfare and product quality. Expansion of the poultry industry has not shifted manure generation away from source counties of the Pennsylvania manureshed. However, poultry’s solid manure is routinely exported from manure nutrient source areas to sink areas through Pennsylvania’s certified manure brokering industry (Meinen et al., 2020).

Figure 3. Transportation distances to harvest for integrators that participated the most in the Pennsylvania Odor Site Assessment Program. Swine travel distances to slaughter are longer than poultry broilers. Blue arrows were arbitrarily placed on the graphic from Figure 2 for illustrative purposes

Future Plans

Smart expansion of animal industries should consider manureshed concepts, which place nutrients in sink areas, but recognize that expansion cannot be influenced by manureshed nutrients alone. Expansion should also consider social forces associated with potential odor conflict, animal health, animal welfare, and animal products. Stakeholders that include producers, integrators, universities, and agencies should work together to strategically influence future manureshed locations and impacts.

On a simple level, and assuming static field-level nutrient use efficiencies, manureshed shifts with expanding industries can occur by 1) relocating animals in nutrient sink areas or 2) transporting manure nutrients out of a source area and to a sink area. The Pennsylvania case study demonstrated that swine industry expansion performed the first strategy and the poultry industry the second strategy. Policies that understand manureshed influences, remove barriers to manure nutrient transport, and facilitate smart expansion can assist with beneficial manureshed management.


Presenting Author

Robert J. Meinen, Senior Extension Associate, The Pennsylvania State University, University Park, PA.

Additional Authors

    • Sheri Spiegal, Range Management Specialist, USDA-ARS, Jornada Experimental Range, Las Cruces, NM.
    • Peter J.A. Kleinman, Research Leader/Soil Scientist, USDA-ARS, Soil Management and Sugar Beet Research Unit, Fort Collins, CO.
    • K. Colton Flynn, Research Soil Scientist, USDA-ARS, Grassland Soil and Water Research Laboratory, Temple, TX.
    • Sarah C. Goslee, Ecologist, USDA-ARS, Pasture Systems and Watershed Management Research Unit, University Park, PA.
    • Robert E. Mikesell, Teaching Professor and Undergraduate Program Coordinator of Animal Science, The Pennsylvania State University, University Park, PA.
    • Clinton Church, Research Chemist, USDA-ARS, Pasture Systems and Watershed Management Research Unit, University Park, PA.
    • Ray B. Bryant, Research Soil Scientist, USDA-ARS, Pasture Systems and Watershed Management Research Unit, University Park, PA.
    • Mark Boggess, Center Director, USDA-ARS, US Meat Animal Research Center, Clay Center, NE.


Meinen, R.J., Spiegal, S., Kleinman P.J.A., Flynn K.C., Goslee S.C, Mikesell, R.E., Church, C., Bryant, R.B., and Boggess, M. 2022. Opportunities to Implement Manureshed Management in the Iowa, North Carolina, and Pennsylvania Swine Industry. Journal or Environmental Quality. Published March 2022 for upcoming Special Edition of JEQ.

Meinen, R.J., D. A. Wijeyakulasuriya, M. Aucoin, and J. E. Berger. 2020. Description and Educational Impact of Pennsylvania’s Manure Hauler and Broker Certification Program. J. Extension 58: 2, v58-2rb4.

NASS. USDA, National Agricultural Statistics Service. 2017. 2017 United States Census of Agriculture. Census Full Report. National Agriculture and Statistics Service Database. United States Department of Agriculture Agricultural Statistics Board, Washington, DC. Available online:


This research was a contribution from the Long-Term Agroecosystem Research (LTAR) network. LTAR is supported by the United States Department of Agriculture, which is an equal opportunity provider and employer.


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