Submitted to: American Dairy Science Association Discover Conference
Publication Type: Abstract Only
Publication Acceptance Date: April 21, 2010
Publication Date: N/A
Interpretive Summary: An interpretive summary is not required.
Technical Abstract: The environmental sustainability of dairy farms is dependent upon a number of air and water quality issues. Atmospheric emissions include hazardous compounds such as ammonia and hydrogen sulfide along with greenhouse gases and their implications with global climate change. Runoff of sediment, phosphorus, and nitrogen effect surface waters and leaching of nitrates can pollute groundwater. Comprehensive, whole farm evaluations are needed to determine the environmental impact of dairy farms, and this must be done along with an assessment of the economics of the farm. This type of evaluation is essentially impossible through experimental measurement. Process-level farm simulation provides a more practical approach, particularly when supported by limited measured data. The Integrated Farm System Model (IFSM) has been used to evaluate the performance, economics, and environmental impacts of a wide range of dairy production systems. The model simulates crop growth, harvest, feed storage, feeding, animal performance, manure production and handling, and crop establishment over many years of weather conditions. Predicted environmental impacts include ammonia emission, nitrate leaching, denitrification losses, greenhouse gas emissions, carbon footprint, sediment erosion, sediment-bound and dissolved phosphorus runoff, and the whole farm balance of each of the major nutrients. As an example application, organic and conventional dairy production systems were compared. For organic systems that rely heavily upon tillage for weed control, sediment and phosphorus losses can be substantially greater than conventional systems using minimum or no tillage practices. When an organic fertilizer such as poultry manure is used, greenhouse gas emissions and the carbon footprint can be increased and the long term accumulation of soil phosphorus and other nutrients can be high relative to the use of inorganic fertilizers. Use of grass-based grazing systems provides another example. Compared to confinement feeding with crop production, use of well managed rotational grazing of perennial grassland increased nitrate leaching to ground water, reduced erosion of sediment, reduced phosphorus runoff losses, reduced ammonia emission, and increased methane and nitrous oxide emissions slightly with little effect on the carbon footprint. During a 20 to 30 year transition from rotated crops to perennial grassland, carbon sequestration may greatly reduce the carbon footprint of pasture based systems. Process-level farm simulation provides an effective tool for integrating environmental and economic issues. Because of the difficulty in quantifying societal concerns and the major differences in environmental concerns that occur among geographic regions, it does not appear feasible to obtain an overall sustainability index for comparing production systems.