Integrating the numerous aspects of a farm system and studying them as a whole...
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 working alongside producers to cultivate and maintain the healthiest and most profitable farm systems possible...
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.
Comparing Manure Application Methods in Farming Systems
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.
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.
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.
Predicting the 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 0.37 to 0.69 kg CO2e per kg of milk produced were found for common production practices. This software provides a unique tool for comprehensive assessment of management effects on greenhouse gas emissions in the production of milk on dairy farms.
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.
Montes, F., Chaoui, H., Rotz, C.A. 2009. Process Modeling of Ammonia Volatilization From aAmonium Solution and Manure Surfaces: A Review With Recommended Models. Transactions of the ASABE. 52(5):1707-1719.
Chaoui, H., Montes, F., Rotz, C.A., Richard, T. 2009. Dissociation and ammonia mass transfer from ammonium solutions and dairy cattle manure. Transactions of the ASABE. 52(5)P1695-1706.
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: www.plantmanagementnetwork.org/sub/fg/research/2009/impact/
Modeling Greenhouse Gas Emissions from Dairy Farms
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 23 and 298 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.
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
With 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?
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.