46 research outputs found
Predicting Management Effects on Ammonia Emissions from Dairy and Beef Farms
No full textRelationships were developed to predict ammonia (NH3) nitrogen losses from cattle manure in animal housing, during manure storage, following field application, and during grazing. Ammonia loss in each phase was predicted using a mechanistic model for NH3 volatilized from the surface of an aqueous solution of ammonium where the NH3 is transported to the free atmosphere through a pathway with finite resistance. Ammonia emission rate was a function of the ammoniacal N content in the manure, ambient temperature, manure pH, manure moisture content, and the exposed manure surface area. Model relationships were calibrated by selecting values for the resistance to NH3 transport for the various loss pathways, which predicted daily and annual emissions similar to those reported in published studies. In further evaluation, these calibrated relationships predicted average annual losses similar to those documented in previous work over a range in climate locations. These relationships were integrated into a whole-farm simulation model to provide a tool for evaluating and comparing long-term nitrogen losses along with other performance, environmental, and economic aspects of farm production. Whole-farm simulations illustrated that the use of a free stall barn, bottom-loaded slurry storage, and direct injection of manure into the soil reduced NH3 emissions by 33% to 50% compared to other commonly used dairy housing and manure handling systems in the northeastern U.S. The improvement in nitrogen utilization more than offset the increased cost in manure handling, providing a small increase in farm profit. The farm model provides a research and teaching tool for evaluating and comparing the economic and environmental sustainability of dairy and beef production systems
Whole farm management to reduce nutrient losses from dairy farms: a simulation study
No full textWhole farm simulation provides a tool for evaluating the impact of nutrient conservation technologies and strategies on dairy farms. A farm simulation model was verified by simulating the production and nutrient flows of the De Marke experimental dairy farm in the Netherlands. Technology such as a low nitrogen emission barn floor, a covered manure storage, manure injection, and the interseeding of grass on corn land to absorb excess nitrogen were used on this farm to reduce nitrogen loss. Simulation of these practices on representative farms in southern Pennsylvania illustrated that nitrogen loss, primarily in the form of ammonia emission, could be reduced by about 35%. The cost of this technology was greater than the value of the nitrogen saved causing a reduction in the annual net return of 74/cow for a 1000-cow farm
Whole Farm Management to Reduce Nutrient Losses From Dairy Farms: A Simulation Study
No full textWhole-farm simulation provides a tool for evaluating long-term impacts of nutrient conservation technologies and strategies on dairy farms. A farm simulation model was verified to predict the production and nutrient flows of the De Marke experimental dairy farm in the Netherlands. On this farm, technologies such as a low ammonia emission barn floor, enclosed manure storage, manure injection into the soil, and intraseeding of a grass cover crop on corn land were used to reduce nitrogen loss and improve nutrient recycling. This experimental farm was simulated over the 1996 to 2003 weather years where predicted production and use of feeds were within 15% of values measured on the actual farm. Simulated nitrogen and phosphorus flows through the farm and losses from the farm were generally within 10% of actual. After this process-based model was found to accurately represent the nutrient conservation technologies used at De Marke, simulation was used to evaluate the environmental and economic impacts of their use on representative farms in southern Pennsylvania. Total nitrogen loss from the farms, primarily in the form of ammonia emission, was reduced by 24% to 55% with a 7% to 45% reduction in P runoff loss. The highest reductions were obtained on a 1,000-cow farm where initial losses were high due to a greater number of animals per unit of cropland. The cost of this technology was greater than the value of the nutrients saved, causing a reduction in the annual net return of 64/cow for the 1,000-cow far
Whole farm management to reduce nutrient losses from dairy farms: a simulation study
No full textWhole farm simulation provides a tool for evaluating the impact of nutrient conservation technologies and strategies on dairy farms. A farm simulation model was verified by simulating the production and nutrient flows of the De Marke experimental dairy farm in the Netherlands. Technology such as a low nitrogen emission barn floor, a covered manure storage, manure injection, and the interseeding of grass on corn land to absorb excess nitrogen were used on this farm to reduce nitrogen loss. Simulation of these practices on representative farms in southern Pennsylvania illustrated that nitrogen loss, primarily in the form of ammonia emission, could be reduced by about 35%. The cost of this technology was greater than the value of the nitrogen saved causing a reduction in the annual net return of 74/cow for a 1000-cow farm
The integration of synchronous and asynchronous design activity records
No full textWith many engineering companies changing their focus from product delivery towards through-life service support, the realisation is that much of the information and knowledge being generated throughout each stage of the design process can aid in both product lifecycle support and also the development of new products. To support these activities, information and knowledge capture systems and models are required, which allow the information to be stored and used thirty years or more into the future. The dichotomy of interest in this paper is that of synchronous and asynchronous working, where engineers may work as part of a group or as individuals and where different forms of record are necessary to adequately capture the processes and rationale employed in each mode. This paper looks at each mode of working in turn and proposes complimentary approaches to information and knowledge capture. The combination of information and knowledge capture performed during both asynchronous and synchronous activities has the potential to create a significantly enhanced overall design process model and record enhancing not only the through-life support of the product but also subsequent projects
Monotonicity Formulas for Diffusion Operators on Manifolds and Carnot Groups, Heat Kernel Asymptotics and Wiener\u27s Criterion on Heisenberg-type Groups
No full textThe contents of this thesis are an assortment of results in analysis and subRiemannian geometry, with a special focus on the Heisenberg group Hn, Heisenbergtype (H-type) groups, and Carnot groups. As we wish for this thesis to be relatively self-contained, the main definitions and background are covered in Chapter 1. This includes basic information about Carnot groups, Hn, H-type groups, diffusion operators, and the curvature dimension inequality. Chapter 2 incorporates excerpts from a paper by N. Garofalo and the author, [42]. In it, we propose a generalization of Almgren’s frequency function N : (0, 1) → R for solutions to the sub-elliptic Laplace equation ΔHu = 0 in the unit ball of a Carnot group of arbitrary step. If the function u has vanishing discrepancy, then the frequency is monotonically non-decreasing, and we are able to prove a form of strong unique continuation for such functions. Chapter 3 grew out of the author seeking parabolic montonicity formulas in the same vein as Almgren’s frequency. These include two types of monotonicity formulas, those of Struwe- and Poon-type [72], [67]. If a diffusion operator L on a complete manifold M satisfies the curvature dimension inequality CD(ρ, n), then we are able to prove that for solutions to L u = ut in M × (0, T), Struwe’s energy monotonicity holds, at least for time values close enough to T. We introduce a new condition, C(ω) where ω ∈ C1(0, T), related to the Hessian of the heat kernel, and are able to prove a Poon-type frequency monotonicity formula when taking into account a weighting factor depending on ω. We also give examples of manifolds satisfying C(ω), the most interesting of which includes the Ornstein-Uhlenbeck operator. Monotonicity of the weighted frequency also implies a form of strong-unique continuation. In Chapter 4, we derive asymptotics for the heat kernel on H-type groups and generalize a gradient bound from a paper of Garofalo and Segala [43] to these groups. This gradient bound in turn implies a strong Harnack inequality and Wiener criterion similar to those found in [31] and [43]
Nitrogen use efficiency: A potential performance indicator and policy tool for dairy farms
No full textEscalating fertilizer and feed costs, declining product prices, and increasing regulations to reduce environmental pollution have created new pressures to improve nutrient use in agricultural production. This study provides an overview of factors and processes that impact nitrogen use efficiency (NUE) in dairy production, identifies practices that may bridge gaps between actual-NUE obtained on commercial farms and potential-NUE obtained under experimental conditions, and explores the possibility of using NUE as a performance indicator and policy tool for dairy production. Actual feed-NUE varies from 16% to 36% and is impacted by of a range of dairy practices; manure/fertilizer-NUE varies from 16% to 77% and is very site-specific; and whole-farm NUE varies from 8% to 64% and declines as stocking rates increase. Optimal stocking rate and manure nitrogen (N) crediting can enhance NUE, increase farm profits, and reduce N loss from dairy farms. NUE could be used to further engage dairy producers in collaborative assessments of gaps between their actual N use and the biological potential of N use, to develop performance goals for N use in various production components, and to monitor and evaluate the impacts of alternative feed, manure and fertilizer management practices on N use, profitability, and environmental outcomes
Organic Dairy Production Systems in Pennsylvania: A Case Study Evaluation
No full textThe current market demand and price for organic milk is encouraging dairy producers, particularly those on smaller farms, to consider organic production as a means for improving the economic viability of their operations. Organic production systems vary widely in scale, in practices, and across agroclimatic settings. Within this context, case studies of 4 actual organic dairy farms were used to characterize existing systems in Pennsylvania. Based on data from these farms, a whole-farm simulation model (Integrated Farm System Model) was used to compare 4 production systems representing organic grass, organic crop, conventional crop with grazing, and conventional confinement production. The performance of each of these systems was simulated over each year of 25 yr of central Pennsylvania weather data. Simulation results indicated that farm level accumulation of soil P and K may be a concern on organic farms that use poultry manure as a primary crop nutrient source, and that erosion and runoff loss of P may be of concern on organic farms producing annual crops because more tillage is required for weed control. Whole-farm budgets with prices that reflect recent conditions showed an economic advantage for organic over conventional production. A sensitivity analysis showed that this economic advantage depended on a higher milk price for producers of organic milk and was influenced by the difference in milk production maintained by herds using organic and conventional systems. Factors found to have little effect on the relative profitability of organic over conventional production included the differences between organic and conventional prices for seed, chemicals, forage, and animals and the overall costs or prices assumed for organic certification, machinery, pasture fencing, fuel, and labor. Thus, at the current organic milk price, relative to other prices, the case study organic production systems seem to provide an option for improving the economic viability of dairy operations of the scale considered in Pennsylvania. To motivate transition to organic systems, the economic advantage found requires the persistence of a substantial difference between conventional and organic raw milk prices
