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Integrated Farming Systems Project
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Integrating the numerous aspects of a farm system and studying them as a whole...

Photo showing various aspects of the farm system that must be integrated in order to study the whole farm.There are many facets to any farm system - from production costs to feeding expenditures to crop growth and harvest, labor and weather. Studying the farm as a comprehensive system that considers how each particular change in the system affects the farm as a whole is an increasingly important step in transferring component research to farm production. Scientists at the USDA ARS combine their extensive research with the hands-on experience of agricultural producers in order to create a farm program that simulates a real farm system. This software, known as the Integrated Farm Systems Model, allows its user to observe how farm changes affect the whole farm, without any of the risks associated with actually making those changes.

Environmental Assessment of U.S. Dairy Farms

/ARSUserFiles/80700500/images/Farm.jpgDairy farms in the United States are diverse. To represent this diversity, comprehensive regional and national assessments are important to define national priorities for sustainable intensification. We estimated important environmental footprints of dairy production systems using process-level simulation and cradle-to-farm gate life cycle assessment. We found that considering everything related to dairy farm production, greenhouse gas (GHG) emissions were equivalent to 1.5% of the estimated U.S. total GHG emission. Fossil energy use was about 0.3% of the U.S. total consumption, and water consumption was roughly 3.0% of the estimated U.S. total freshwater use. While these environmental footprints represent a small portion of the respective national inventories, the dairy industry’s contribution to reactive nitrogen losses appears to be considerably greater. The major form of nitrogen loss is ammonia, where dairy farms were found to contribute 19 – 24% of national inventories of ammonia emissions. While strategies are available to reduce these emissions, finding economical and sustainable solutions that do not result in pollution swapping remains a challenge for the dairy industry.

Rotz, C.A., R. Stout, A. Leytem, G. Feyereisen, H. Waldrip, G. Thoma, M. Holly, D. Bjorneberg, J. Baker, P. Vadas and P. Kleinman. 2021. Environmental assessment of United States dairy farms. J. Cleaner Prod. (2021), doi:

Rotz, C.A., R.C. Stout, M.A. Holly, and P.J.A. Kleinman. 2020. Regional environmental assessment of dairy farms. J. Dairy Sci. 103:3275-3288.

Rotz, C.A., M. Holly, A. de Long, F. Egan and P. J.A. Kleinman. 2020. An environmental assessment of grass-based dairy production in the northeastern United States. Agric. Systems 184.

Holly, M.A., K.M. Gunn, C. A. Rotz, P.J.A. Kleinman. 2019. Management characteristics of Pennsylvania dairy farms. Appl. Anim. Sci. 35:325-338.

Environmental Footprints of U.S. Beef

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Environmental impacts of beef cattle production and their effect on the overall sustainability of beef have become a national and international concern. Surveys and visits of farms, ranches and feedlots were conducted throughout seven regions of the U.S. (Northeast, Southeast, Midwest, Northern Plains, Southern Plains, Northwest, and Southwest) to determine common practices and characteristics of cattle production. Simulations of representative cattle operations quantified the performance and environmental impacts of production in each region and the full U.S.  A farm-gate life cycle assessment was used to quantify resource use and emissions for all production systems including traditional beef breeds and cull animals from the dairy industry. Compared to total national inventories, beef cattle production produced 3.7% of the GHG emissions and used 0.7% of the fossil energy and 6% of the fresh water consumed in the U.S.  Based upon this farmgate information, a full cradle-to-grave life cycle assessment of beef was conducted that included harvest, processing, consumption, and the waste created for a comprehensive set of environmental impact categories. For many of these categories, electricity consumption across the supply chain was a substantial driver of environmental impact. Food loss and waste were major contributors to all categories making waste one of the greatest impacts for environmental sustainability. This highlights the importance of engaging the full supply chain in understanding the impacts of the industry. This assessment establishes a current profile for the environmental sustainability of US beef which provides a baseline to quantify potential national benefits as mitigation strategies are developed and implemented.

Putman, B., C.A. Rotz, and G. Thoma. 2023. A comprehensive environmental assessment of beef production and consumption in the United States. J. Cleaner Prod. 402 (in press)

Rotz, C. A., S. Asem-Hiablie, S. Place and G. Thoma. 2019. Environmental footprints of beef cattle production in the United States. Agric. Systems 169:1-13.

Asem-Hiablie, S., T. Battagliese, K. R. Stackhouse-Lawson, and C. A. Rotz. 2018. A Life Cycle Assessment of the Environmental Impacts of a Beef System in the United States. J Life Cycle Assess.

Rotz, C.A., S. Asem-Hiablie, J. Dillon and H. Bonifacio. 2015. Cradle-to-farm gate environmental footprints of beef cattle production in Kansas, Oklahoma, and Texas. J. Anim. Sci. 93:2509-2519.

Rotz, C.A., B.J. Isenberg, K.R. Stackhouse-Lawson, and J. Pollak. 2013. A simulation-based approach for evaluating and comparing the environmental footprints of beef production systems. J. Animal Sci. 91:5427-5437.

Double Cropping and Intercropping Systems

/ARSUserFiles/80700500/images/Intercrop.JPGDouble cropping, cover cropping, interseeding and subsurface manure application are practices that dairy farmers can adopt to reduce gaseous emissions to air and nutrient and sediment losses from fields during surface runoff events. Projected future changes in temperature, precipitation, and atmospheric carbon dioxide present a challenge and perhaps opportunity for future agricultural production. Projected changes may exacerbate environmental impacts of dairy farms, but also improve production with proper adaptation. Farm simulations suggest that interseeding generally outperforms cover crops in reducing nitrogen, phosphorus, and sediment losses, and additional costs for these practices increased total farm production costs by no more than 2%. We evaluated whole-farm production, environmental and economic impacts of double cropping corn and rye silages along with subsurface application of manure on a representative dairy farm using recent historical and projected mid-century climate. We found that double cropping benefited greatly from the projected increase in growing season length providing additional forage that was less susceptible to summer droughts. Placing manure below the soil surface countered projected increases in nutrient losses by midcentury due to increased temperatures and storm intensities. Our results suggest that use of this more intensive cropping systems along with improved manure application technology can help mitigate dairy farm environmental impacts now and even more in the future without significantly increasing total production costs.

Castano-Sanchez, J.P., H. D. Karsten, C. A.  Rotz. 2022. Double cropping and manure management mitigate the environmental impact of a dairy farm under present and future climate. Agric. Systems 196:103326.

Barnes, R.G., C.A. Rotz, H.E. Preisendanz, J.E. Watson, H.A. Elliott, T.L. Veith, C. Williams, and K.J. Brasier. 2021. Cover cropping and interseeding management practices to improve runoff quality from dairy farms in Central Pennsylvania. Trans. ASABE. 64(4):1403-1413.

Ranck, E., Holden, L., Dillon, J., Rotz, C.A., Soder, K.J. 2020. Economic and environmental impact of double cropping winter annuals and corn using the integrated farm system model. J. Dairy Sci. 103:3804–3815.

Southwest Beef Systems

/ARSUserFiles/80700500/images/SWbeef.jpegThe southwestern United States is projected to experience an increasingly warmer and drier climate, which will affect cattle production systems prevalent in the region. Adaptation strategies are needed that will not compromise environmental quality or profitability. Production systems using desert adapted Rarámuri Criollo cattle and crossbreds of Criollo with Angus cattle were studied to determine potential environmental and economic benefits compared to the traditional Angus cattle production systems currently used in this region. Crossbred cattle production with grass finishing in the Southwest or in the Northern Plains outperformed on most environmental variables with lower production costs but this option emitted more greenhouse gas than grain finishing of Angus cattle in the region. Grass finishing in more temperate regions such as the Northern Plains may provide a more stable meat supply chain than grass finishing in the Southwest due to lower risk and less severe consequences of drought. As the climate in the southwest region becomes drier in the future, use of Criollo cattle and their crossbreds can provide more sustainable cattle production systems for producing food in this region.

Castano-Sanchez, J., C. A. Rotz, M. M. McIntosh, C. Tolle, C.A. Gifford, G.C. Duff, and S.A. Spiegal. 2023. Grass finishing of Criollo cattle can provide an environmentally preferred and cost effective meat supply chain from United States drylands. Agric. Systems. 210:103694. DOI:10.1016/j.agsy.2023.103694

Spiegal, S., A.F. Cibils, B.T. Bestelmeyer, J.L. Steiner, R.E. Estel, D.W. Archer, B.W. Auvermann, S.V. Bestelmeyer, L.E. Boucheron, H. Cao, A.R. Cox, D.Devlin, G.C. Duff, K.K. Ehlers, E.H. Elias, C.A. Gifford, A.L. Gonzalez, J.P. Holland, J.S. Jennings, A.M. Marshall, D.I. McCracken, M.M. McIntosh, R. Miller, M. Musumba, R. Paulin, S.E. Place, M. Redd, C.A. Rotz, C. Tolle and A. Waterhouse. 2020. Beef production in the southwestern United States: Strategies toward sustainability. Front. Sustain. Food Syst. 4:114. doi: 10.3389/fsufs.2020.00114.

Steiner, J. L., C. B. Brandani, A. Chappell, J. Castaño-Sanchez, M. Hoellrich, M. M. McIntosh, S. Nyamuryekung'e, N. Pietrasiak, A. Rotz, and N. P. Webb. 2023. Distinctive dryland soil carbon transformations and management: Insights from arid rangelands of southwestern United States. Adv. Soil Sci. (accepted 7/19/2022).

Best Management Practices to Improve the Sustainability of Dairy Farms

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Implementation of Beneficial Management Practices (BMPs) can mitigate GHG emissions and nutrient losses and reduce the environmental impact of dairy production, but comprehensive, whole-farm studies that evaluate the efficacy of multiple BMPs to reduce multiple environmental impacts and that include an assessment of productivity and farm profitability, are scarce. IFSM was used to assess the efficacy of individual BMPs to reduce the carbon (C) footprint and total nitrogen (N) and phosphorus (P) losses along with effects on farm profitability of representative dairy farms in the Great Lakes region of the U.S. Reductions in the C footprint expressed per unit of milk produced were greatest with individual manure management interventions followed by dietary manipulations. Field management BMPs had a modest effect on reducing the C footprint but showed substantial potential to reduce N and P losses. A combination of mitigation strategies substantially reduced the C footprint and nutrient losses, while increasing milk production and the net return per cow. Looking to the future, a comprehensive assessment of the effects of climate change on farm environmental performance and productivity was assessed as influenced by these BMPs. Using climate projections for high and low emission scenarios, we found that the environmental impact of the dairy farms generally increased by mid-century, if no mitigation measures were taken. Adoption of the BMPs substantially reduced the GHG emissions and nutrient losses from the farms under current climate conditions and stabilized the environmental impact in future climate conditions, while maintaining farm productivity (milk and feed production). Overall, our analysis shows the potential for implementing an integrated set of BMPs to reduce GHG emissions and nutrient losses of dairy farms in the Great Lakes region now and for the future without sacrificing productivity or profit to the farmer.

Veltman, K., C. A. Rotz, L. Chase, J. Cooper, C.E. Forest, P. Ingraham, R. C. Izaurralde, C. D. Jones, R.E. Nicholas, M. Ruark, W. Salas, G. Thoma, and O. Jolliet. 2021. Assessing and reducing the environmental impact of dairy production systems in the northern US in a changing climate. Agric. Systems 192:1-14.

Veltman, K., C. A. Rotz, L. Chase, J. Cooper, P. Ingraham, R. C. Izaurralde, C. D. Jones, R. Gaillard, R. A. Larsson, M. Ruark, W. Salas, G. Thoma, and O. Jolliet. 2018. A quantitative assessment of beneficial management practices to reduce carbon and reactive nitrogen footprints and phosphorus losses of dairy farms in the Great Lakes region of the United States. Agric. Systems 166:10-25.

Kim, D., N. Stoddart, C. A. Rotz, K. Veltman, L. Chase, J. Cooper, P. Ingraham, R. C. Izaurralde, C. D. Jones, R. Gaillard, H. A. Aguirre-Villegas, R. A. Larson, M. Ruark, W. Salas, O. Jolliet, G. J. Thoma. 2019. Analysis of Beneficial Management Practices to Mitigate Environmental Impacts in Dairy Production Systems around the Great Lakes. Agric. Systems 176:1-12.

Climate Change and Adaptation Strategies

/ARSUserFiles/80700500/images/Climate.jpgClimate change may affect many aspects of dairy production, including growing season length, crop growth processes, harvest timing and losses, heat stress on cattle, nutrient emissions and losses, and ultimately farm profitability. To assess the sensitivity of dairy farms to climate change, IFSM was used to simulate representative dairy farms over 25-yr periods using recent historical climate and projected mid and end-of-century climate. Base farms reflected current production practices with recent climate in southern Pennsylvania, northern New York, central Wisconsin, southern Idaho, central California, and central Texas. We explored management changes to adapt the farms to future climate by modifying crop varieties and planting and harvest dates, and the use of double cropping of small-grain silage and corn silage in northern regions. Responses to projected climate change varied across the six locations, but common trends were found. For most locations, projected climate improved forage production but decreased corn grain production. Higher temperatures and changes in precipitation patterns increased gaseous emissions and nutrient losses from farms. For most scenarios, farm profitability was maintained in projected climate through adaptations in management. Similar results have also been found for dairy farms in Canada. These simulation studies illustrate that climate and farm simulation models can provide valuable information for planning and adapting our dairy farms to changing climate.

Rotz, C.A., R.H. Skinner, A.M.K. Stoner, and K. Hayhoe. 2016. Evaluating greenhouse gas mitigation and climate change adaptation in dairy production using farm simulation. Trans. ASABE 59(6):1771-1781.

Rotz, C.A., R.H. Skinner, A.M.K. Stoner, and K. Hayhoe. 2016. Farm simulation can help dairy production systems adapt to climate change. In J. Hatfield and D. Fleisher. Advances in Agricultural Modeling, Vol. 7 pp 91-124. ASA-CSSA-SSA, Madison, WI.

Thivierge, M.-N., G. Jégo, G. Bélanger, M.H. Chantigny, C.A. Rotz, É. Charbonneau, V.S. Baron, and B. Qian. 2017. Projected impact of future climate conditions on the agronomic and environmental performance of Canadian dairy farms. Agric. Syst. 157:241–257.

Cordeiro, M.R.C., A. Rotz, R. Kroebel, K. A. Beauchemin, D. Hunt, S. Bittman, K. M. Koenig, and D. B. McKenzie. 2019. Prospects of forage production in northern regions under climate and land-use changes: a case-study of a dairy farm in Newfoundland, Canada. Agronomy 9:31,

Thivierge, M-N, G. Bélanger, G. Jégo, S. Delmotte, C. A. Rotz, and É. Charbonneau. 2023. Perennial forages in cold-humid areas: Adaptation and resilience-building strategies toward climate change. Agron. J. 2023:1-24. DOI: 10.1002/agj2.21354

Carbon Footprint and Ammonia Emissions of California Beef Production Systems

/ARSUserFiles/80700500/images/quickLinks/CA beef.jpgA partial life cycle assessment (LCA) was conducted using IFSM to estimate GHG and NH3 emissions from representative beef production systems in California. Simulated systems included cow-calf, stocker, and feedlot phases for traditional British beef breeds and calf ranch and feedlot phases for Holstein steers. An evaluation of differing production management strategies resulted in ammonia emissions ranging from 98 ± 13 to 141 ± 27 g/kg HCW and carbon footprints of 10.7 ± 1.4 to 22.6 ± 2.0 kg CO2e/kg HCW. Within the British beef production cycle, the cow-calf phase was responsible for 69 to 72% of total GHG emissions with 17 to 27% from feedlot sources. Holstein steers that entered the beef production system as a by-product of dairy production had the lowest carbon footprint because emissions associated with their mothers were primarily attributed to milk rather than meat production. For the Holstein system, the feedlot phase was responsible for 91% of the total GHG emission, while the calf-ranch phase was responsible for 7% with the remaining 2% from transportation. Use of growth promoting technologies decreased NH3 emission from the full production system by 14 g/kg HCW, or 13%. Over full production systems, decreases in C footprint were relatively small at 9% and 5% for Angus and Holstein beef, respectively. This simulation study provides baseline emissions data for California beef production systems and indicates where mitigation strategies can be most effective in reducing emissions.

Stackhouse-Lawson, K.R., C.A. Rotz, J.W. Oltjen, and F.M. Mitloehner. 2012. Carbon footprint and ammonia emissions of California beef production systems. J. Anim. Sci. 90:4641-4655.

Stackhouse-Lawson, K.R., C.A. Rotz, J.W. Oltjen, and F.M. Mitloehner. 2012. Growth-promoting technologies decrease the carbon footprint, ammonia emissions, and costs of California beef production systems. J. Anim. Sci. 90:4656-4665.

Comparing Manure Application Methods in Farming Systems

Manure injection device for applying manure below the soil surface.Animal manure provides nutrient rich organic matter that can serve as a valuable fertilizer resource for crop production. In a well managed production system, manure nutrients are returned to the soil where they are used to produce feed crops for animal production. The problem in this recycling of nutrients is that losses occur, and these losses adversely affect the environment. Nutrient losses of greatest concern are gaseous emission of ammonia, nitrate leaching to ground water, and surface runoff of phosphorus. Farm management strategies are desired to minimize these nutrient losses and maximize their use in crop production without adversely affecting farm profitability. Computer simulation of farms, supported by field research, was used to evaluate and compare the performance, environmental impact, and economics of alternative manure application methods. Reductions in ammonia emission and phosphorus runoff losses were obtained through improved incorporation of manure. Use of a shallow disk injection device for applying manure below the soil surface generally provided the lowest nutrient losses without substantially reducing farm profitability. Use of band application of manure along with soil aeration provided less environmental benefit, and the increased costs of production were generally greater than the economic benefit received. This information helps animal producers choose manure application equipment that reduces their impact on the environment while maintaining farm profitability.

Rotz, C.A., Kleinman, P.J.A., Dell, C.J., Veith, T.L., Beegle, D. 2011. Environmental and economic comparisons of manure application methods in farming systems. Journal of Environmental Quality. 40:438-448.

Duncan, E.W., P.J.A. Kleinman, D.B. Beegle, and C.A. Rotz. 2017. Coupling dairy manure storage with injection to improve nitrogen management: Whole-farm simulation using the Integrated Farm System Model. Agric. Environ. Letters 2:160048.

Quantifying Ethanol Emission from Corn Silage

Smog is a widespread form of air pollution in the United States and globally that is recognized as a cause of premature death. Smog contains a mixture of pollutants that is usually quantified by measuring ozone gas, a dominant irritant in smog. Smog and ozone are created in the atmosphere when volatile organic compounds (VOCs) react with oxides of nitrogen (NOx). Reductions in VOC and NOx emissions from vehicles and industry over the past 40 years have resulted in a decline in ozone concentrations in the US. However, other sources of VOCs may be important in some areas. Recent measurements indicate that dairy farms may be a major source of VOCs in California. Measurements show that silage, a fermented cattle feed, and silage-containing mixed feed are major sources of VOC emissions on dairy farms. However, the amount of VOCs emitted from dairy farms is not accurately known. We measured emission rates of ethanol (a dominant silage VOC) from corn silage. After exposure to moving air, ethanol emission rate declined drastically over time, showing that individual point estimates of emission rate are not sufficient. Emission rate and cumulative emission increased with air velocity, temperature, particle size, and exposed surface area. This work provides estimates of ethanol emission rates from silage on farms, and provides information that should be incorporated into procedures for measuring and modeling VOC emission from silage.

Bonifacio, H.F., C.A. Rotz, S.D. Hafner, F. Montes, M. Cohen and F.M. Mitloehner. 2017. A process-based emission model of volatile organic compounds from silage sources on farms. Atmos. Environ. 152:85-97.

Hafner, S.D., Montes, F., Rotz, C.A., Mitloehner, F.M. 2010. Ethanol emission from loose corn silage and exposed silage particles. Atmospheric Environment. 44:4172-4180.

Montes, F., Hafner, S.D., Rotz, C.A., Mitloehner, F.M. 2010. Temperature and air velocity effects on ethanol emission from corn silage with the characteristics of an exposed silo face. Atmospheric Environment. 44(16):1987-1995.

Carbon Footprint of Dairy Farms

Atmospheric concentrations of greenhouse gases have steadily increased throughout the twentieth century, and this is thought to be contributing to an increase in the surface temperature of the earth and related changes in global climate. Although there is still much uncertainty in specific numbers, agriculture appears to have a significant role in this international issue with livestock production being the major contributor. Animals, particularly ruminants such as dairy animals, release greenhouse gases during the digestion of feed with further emissions during the handling of their manure. Greenhouse gases emitted from dairy farms include carbon dioxide, methane and nitrous oxide, with various sources and sinks throughout the farm. Measuring the assimilation and emission of these gases from farms is difficult, relatively inaccurate, and very expensive. Emissions are also very dependent upon farm management, the climate and other factors, so large differences can occur among farms. Relationships for predicting all important sources and sinks of the three greenhouse gases on dairy farms were integrated in a comprehensive model that predicts net farm emission in carbon dioxide equivalent units. Carbon footprints of 0.7 to 1.2 kg CO2e per kg of milk produced have been found for common production practices. The DairyGEM software provides a unique tool for comprehensive assessment of management effects on greenhouse gas and other gaseous emissions in the production of milk on dairy farms.

Rotz, C.A. 2018. Modeling greenhouse gas emissions from dairy farms. J. Dairy Sci. 101:6675-6690.

Rotz, C.A. and G. Thoma. 2017. Assessing the carbon footprint of dairy production systems. p. 19-31, In D.K. Beede (ed). Large Dairy Herd Management, 3rd ed., Am. Dairy Sci. Assoc., Champaign, IL.

Rotz, C.A., Montes, F., Chianese, D.S. 2010. The carbon footprint of dairy production systems through partial life cycle assessment. Journal of Dairy Science. 93(3):1266-1282.

Modeling of Ammonia Emission Processes

An important emission from animal-producing farms is ammonia. The amount of ammonia emitted is heavily influenced by management practices, which vary considerably among farms. Therefore, the use of emission factors such as a loss per animal unit can only provide a general estimate of the emissions from a given farm. A more accurate approach is to use computer simulation to estimate emissions where all of the important components of the farm and their interactions are considered. An extensive review of existing research literature was conducted, summarized, and used to develop a robust model for predicting ammonia emission from the surface of an ammonium containing solution such as manure. This refined model of ammonia emission provides a key component for software tools being developed to estimate gaseous emissions from livestock farms. With these tools, producers and their consultants will be able to estimate ammonia emissions from specific farms as influenced by the management of each farm. Technologies and strategies for reducing emissions can also be evaluated to help develop more environmentally friendly and profitable farms.

Rotz, C.A., F. Montes, S.D. Hafner, A.J. Heber, R.H. Grant. 2014. Ammonia emission model for whole farm evaluation of dairy production systems. J. Environ. Quality 43:1143-1158.

Bonifacio, H.F., C.A. Rotz, A.B. Leytem, H.M. Waldrip, and R.W. Todd. 2015. Process-based modeling of ammonia and nitrous oxide emissions from open lot beef and dairy facilities. Trans. ASABE 58(3): 827-846.

Waldrip, H.M., C. A. Rotz, S. D. Hafner, R. W. Todd, and N. A. Cole. 2014. Process-based modeling of ammonia emission from beef cattle feedyards with the Integrated Farm Systems Model. J. Environ. Quality 43:1159-1168.

Montes, F., Chaoui, H., Rotz, C.A. 2009. Process Modeling of Ammonia Volatilization From ammonium Solution and Manure Surfaces: A Review With Recommended Models. Transactions of the ASABE. 52(5):1707-1719.

Leytem, A.B., D.L. Bjorneberg, C.A. Rotz, L.E. Moraes, E. Kebreab, and R.S. Dungan. 2018. Ammonia emissions from dairy lagoons in the western U.S. Trans. ASABE 61:1001-1015.

Grazing can Reduce the Environmental Impact of Dairy Production Systems

Dairy production, like other livestock production systems, has various environmental impacts involving both water and air quality issues. The use of well-managed rotational grazing as a production strategy provides benefits to the producer and society for many, but not necessarily all, environmental concerns. An experimental comparison of the diverse environmental impacts among dairy production strategies is not feasible; there are too many factors to be considered, and these factors are highly interrelated and influenced by soil type, weather, and management decisions. Computer simulation offers the only practical means of systematically comparing farming systems. A comprehensive simulation analysis illustrated the environmental impacts of four diverse dairy production systems in Pennsylvania that used confinement feeding and managed rotational grazing strategies. Grazing systems greatly reduced soil erosion and sediment-bound phosphorus runoff. Runoff of soluble phosphorus and volatilization of ammonia were also reduced, but nitrate leaching loss was increased. The net greenhouse gas emission or carbon footprint of milk production was reduced just a little through the use of grazing, but during the transition of row cropland to perennial grassland, soil carbon sequestration greatly reduced the carbon footprint of grass-based systems. These environmental benefits should be used to encourage greater adoption of managed rotational grazing in regions where this technology is well adapted.

Rotz, C.A., Soder, K.J., Skinner, R.H., Dell, C.J., Kleinman, P.J., Schmidt, J.P., Bryant, R.B. 2009. Grazing can reduce the environmental impact of dairy production systems. Forage and Grazinglands. Available at: 

Belflower, J.B., J.K. Bernard, D.K. Gattie, D.W. Hancock, L.M. Risse, C.A. Rotz. 2012. A case study of the potential environmental impacts of different dairy production systems in Georgia. Agric. Systems 108:84-93.

Modeling Greenhouse Gas Emissions from Dairy Farms

Cows fed diets with reduced levels of phosphorus can reduce excess phosphorus on the farm and improve profit.The Intergovernmental Panel on Climate Change has reported that it is "extremely likely" that anthropogenic emissions of greenhouse gases are causing a change in the global climate. Although many mitigation plans currently focus on reducing carbon dioxide (CO2) emissions, methane (CH4) and nitrous oxide (N2O) are stronger greenhouse gases with global warming potentials around 28 and 265 times that of CO2, respectively. The claim has been made that globally, livestock emit more CH4 and N2O in CO2 equivalent units than is emitted through the burning of fossil fuels for transportation. Therefore, quantifying and reducing these emissions from livestock farms is important for developing sustainable production systems. Farm emissions are difficult and expensive to measure. A more practical approach is to use process-level modeling and computer simulation to estimate farm emissions and analyze how management affects these emissions. A whole-farm simulation model was extended to include emissions of CH4, N2O and CO2 to obtain a comprehensive tool for evaluating management effects on farm performance, profitability, and environmental pollutants such as nitrate leaching, ammonia volatilization, and phosphorus runoff loss along with greenhouse gas emissions. Farm simulations showed that increasing forage production and use in animal diets increased CH4 emission with little impact on the global warming potential over all greenhouse gas emissions from the farm. Using a manure storage cover and burning the captured biogas reduced farm emission of CH4 by 30% with a 22% reduction in the net farm emission of greenhouse gases. Incorporation of greenhouse gas emissions in the farm model provides a tool for estimating whole-farm emissions and evaluating proposed reduction strategies along with their impact on net greenhouse gas emission and other environmental and economic measures.

Rotz, C.A. 2018. Modeling Greenhouse gas emissions from dairy farms. J. Dairy Sci. 101:6675-6690.

Rotz, C.A. and G. Thoma. 2017. Assessing the carbon footprint of dairy production systems. p. 19-31, In D.K. Beede (ed). Large Dairy Herd Management, 3rd ed., Am. Dairy Sci. Assoc., Champaign, IL.

Chianese, D.S., Rotz, C.A., Richard, T.L. 2009. Simulation of methane emissions from dairy farms to assess greenhouse gas reduction strategies. Transactions of the ASABE. 52(4):1313-1323.

Chianese, D.S., Rotz, C.A., Richard, T.L. 2009. Simulation of nitrous oxide emissions from dairy farms to assess greenhouse gas reduction strategies. Transactions of the ASABE. 52(4):1325-1335.

Chianese, D.S., Rotz, C.A., Richard, T.L. 2009. Simulation of carbon dioxide emissions from dairy farms to assess greenhouse gas reduction strategies. Transactions of the ASABE. 52(4):1301-1312.

Determining the Appropriate Detail for Pasture Models

Heifers grazing on a research plot at Penn State UniversityWith the increasing interest in sequestering carbon in agricultural soils, models are needed that can predict management and environmental effects on the processes controlling carbon gain and loss from pastures. Such models must be complex enough to capture key processes yet simple enough to allow for parameterization with readily available data. Two pasture growth models that shared many common features, but differed in model complexity, were incorporated into the Integrated Farm System Model (IFSM) and compared for their ability to predict photosynthesis, forage yield, and shoot respiration. The main difference between models was the inclusion of roots in the complex model and their absence in the simple model. Simulated shoot respiration was always greater in the simple model but no field data were available to determine which model provided the best estimate of observed respiration rates. On average, little difference existed between models in their ability to predict photosynthesis and yield although large differences for specific years and sites were sometimes observed. Our results suggest that the ability of the complex model to simulate roots was not needed to adequately simulate photosynthesis, respiration and shoot growth on these pasture systems.

Skinner, R.H., Corson, M.S., Rotz, C.A. 2008. Comparison of Two Pasture Growth Models of Differing Complexity. Agricultural Systems. 99:35-43.

Modeling of Multiple Species Pasture Growth

Many dairy or beef producers in the northeastern US graze their cattle on pasture but rely on just one of several grass species to provide forage. Recent field research has shown that mixtures of more than one forage species -- a grass plus a nitrogen-fixing legume, for example -- often can improve the yields or lessen the environmental impacts of pastures. Computer simulation provides a tool to predict the effects of multiple-species pastures under a wide variety of management strategies and weather conditions. A whole-farm simulation model was modified to allow prediction of multiple-species pastures. This model will help its users estimate the effects of multiple-species pastures on environmental impacts and profitability of Northeastern dairy or beef farms.

Corson, M.S., Rotz, C.A., Skinner, R.H., Sanderson, M.A. 2007. Adaptation and evaluation of the integrated farm system model to simulate temperate multiple-species pastures. Agricultural Systems 94(2):502-508.

Grass-Based Dairy Production Provides a Viable Option for Producing Organic Milk in Pennsylvania

Most dairy farms in Pennsylvania remain relatively small in size, but these farms are having difficulty maintaining viable operations. The major issues faced are low profit and environmental concerns. Production costs remain high relative to the price of milk sold, compromising profitability at this smaller scale of operation. Environmental concerns are primarily related to nitrogen and phosphorus losses to ground and surface waters. Reducing these losses requires improved technologies and strategies, which often increase production costs. To reduce production costs, some are turning to greater use of pasture with rotational grazing of animals. To further improve profit, some are transitioning to organic production to obtain a greater price for their milk sold. A computer simulation study, based upon four actual farms in Pennsylvania, was done to evaluate the economic and environmental benefits of small farms using rotational grazing of pastures with either organic or conventional practices. Use of organic production increased farm profitability, but there were environmental concerns related to increased accumulation of soil phosphorus and greater potential for erosion and phosphorus runoff to surface waters. The current economic benefit of organic production may encourage more grass-based dairy producers to transition to organic, so more attention must be given to strategies that better utilize farm nutrients and reduce losses to the environment.

Rotz, C.A., Karsten, H.D., Weaver, R.D. 2008. Grass-Based Dairy Production Provides a Viable Option for Producing Organic Milk in Pennsylvania. Online. Forage and Grazinglands. doi:10.1049/FG-2008-1212-01-RS.

Rotz, C.A., Kamphuis, G.H., Karsten, H.D., Weaver, R.D. 2007. Organic dairy production systems in Pennsylvania: a case study evaluation. Journal of Dairy Science. 90:3961-3979.

Predicting Management Effects on Phosphorus Loss from Farms

The U. S. Environmental Protection Agency estimates that there are 22,000 impaired surface waters (e.g., lakes, streams, reservoirs) in the country, with 11% of these impairments due to nutrients originating primarily from agriculture. Because phosphorus (P) is a primary control of eutrophication in surface waters, P pollution from agriculture is a major concern. Research on P management is focused on implementing alternative management practices to reduce the amount lost from farms. If these management strategies reduce the profitability of farms though, the practices are unlikely to be implemented. Thus, strategies to reduce P pollution from farms must be evaluated along with other environmental factors and the economics of the farm. Computer models provide a cost-effective and relatively rapid method of analyzing farm management scenarios. The Integrated Farm System Model was expanded to include a component that predicts the effects of management on farm-level P loss. The model was used to illustrate that P loss from dairy farms could be reduced up to 50% through the use of conservation tillage practices and improved manure application methods while maintaining or improving farm profit. The expanded farm model provides a tool for evaluating management effects on P and N losses to the environment along with farm economics.

Sedorovich, D.M., Rotz, C.A., Vadas, P.A., Harmel, R.D. 2007. Predicting management effects on phosphorus loss from farming systems. Transactions of the American Society of Agricultural Engineers. 50(4):1443-1453.

Reducing Nutrient Losses from Dairy Farms

Profitability and environmental impact are two constraints that threaten the long term sustainability of dairy farms in America and other developed countries. As the dairy industry adjusts to a more global market, the real price of milk has been stable or declining while production costs increase. Environmental concerns are also growing as we learn more about nutrient losses and their impacts. Steps can be taken to better utilize farm nutrients and reduce losses to the environment, but these changes often increase production costs and reduce net income. Thus, the problem of reducing potential environmental impacts while maintaining or improving profitability is complex, requiring a comprehensive evaluation of the farm in its environment. A farm simulation model was verified to accurately represent nutrient conservation technologies used on an experimental farm in the Netherlands. The farm model was then used to determine the impacts of using these technologies on typical American dairy farms. Nutrient conserving technologies included a low emission barn floor, an enclosed manure storage, manure injection into the soil, and the underseeding of a grass cover crop on corn land. Use of these technologies was found to reduce nitrogen losses, primarily in the form of ammonia emission, by more than 25% with as much as a 50% reduction in phosphorus runoff loss to surface waters. The cost of using these technologies was relatively high though, reducing farm profit by up to 16%. Farm planners and policymakers must develop procedures for implementing the nutrient conservation processes desired to protect our environment in a cost effective or subsidized manner that maintains profitable farms.

Rotz, C.A., Oenema, J., Van Kuelen, H. 2006. Whole farm management to reduce nutrient losses from dairy farms: a simulation study. Applied Engineering in Agriculture. 22(5):773-784.

Modeling of Beef Production

With tighter profit margins and increasing environmental constraints, strategic planning of farm production systems is becoming both more important and more difficult. Animal production is complex, with a number of interacting processes that include crop and pasture production, crop harvest, feed storage, grazing, feeding, and manure handling. Computer simulation provides a useful means of integrating these processes to predict the long-term performance, environmental impact, and economics of production strategies. A dairy farm model, called the Dairy Forage System Model or DAFOSYM, provides this type of tool for evaluating dairy farms. We created a more comprehensive beef farm model by developing and integrating a beef animal component with DAFOSYM. This new Integrated Farm System Model provides a unique research and education tool for evaluating the performance, environmental impact, and economics of beef farms over many weather years. Researchers will use the model to evaluate, compare, and develop new beef production systems that are more environmentally and economically sustainable. The model can also be used through classroom, laboratory, and individual use to study the whole-farm impact of management and technological changes.

Rotz, C.A., Buckmaster, D.R., Comerford, J.W. 2004. A beef herd model for use in whole farm simulation. Journal of Animal Science. 83:231-242.


Is Robotic Milking a Viable Option?

Cow being milked by an automatic (robotic) milker.Automatic or robotic milking systems are now reliable and practical for routine use on dairy farms. In Europe, at least 1,000 farms are using automatic milking, and several units are operating on Canadian and US farms. Automatic milking systems offer two major benefits to dairy producers: an elimination of the labor required for the routine chore of milking and an increase in milk production. The initial cost of this milking equipment is high though, and the long-term economic benefit is dependent upon farm size and other farm management characteristics. A comprehensive whole-farm study showed that automatic milking systems were economically competitive with traditional milking systems on a farm size of around 60 cows. At this farm size, the capacity of one automatic unit was well matched to the number of animals milked, which made efficient use of this costly milking equipment. When multiple units were well matched to herd size (around 120, 180 and 240 cows), farm profitability using automatic milking approached that with traditional systems. On other farm sizes, the automatic milking equipment was not efficiently used and farm profit was less than that of traditional milking systems. As this technology is developed further, a reduction in the initial equipment cost and an increase in the useful life of the equipment will improve the potential economic benefit of automatic milking.

Rotz, C.A., Coiner, C.U., Soder, K.J. 2003. Economic impact of automatic milking systems on dairy farms. Journal of Dairy Science. 86(12):4167-4177.

Rotz, C. A., C. U. Coiner, and K. J. Soder. 2001. Economics of robotic milking on a dairy farm in the United States. p. 115-122. In T. Juliszewski (ed), Farm Work Science Facing the Challenges of the XXI Century. Proc. XXIX CIOSTA-CIGR V Congress. June 25-27, Krakow, Poland. Wageningen Pers, Wageningen, The Netherlands.