|Rotz, Clarence - Al|
|Van Kuelen, H|
Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2006
Publication Date: 10/5/2006
Citation: 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. Interpretive Summary: 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.
Technical Abstract: Whole farm simulation provides a tool for evaluating the long term impact of nutrient conservation technologies and strategies on dairy farms. The Integrated Farm System Model was verified to simulate the production and nutrient flows of the De Marke experimental dairy farm in the Netherlands. On this farm, technology such as a low ammonia emission barn floor, enclosed manure storage, manure injection into the soil, and the underseeding 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 feed production and use were within 15% of values measured on the farm. Simulated nitrogen and phosphorus flows within the farm and losses from the farm were generally within 1 to 10% of actual. After the model was found to accurately represent the nutrient conservation technology of De Marke, simulation was used to evaluate the environmental and economic impacts of their use on representative farms in Pennsylvania. Total nitrogen loss from the farms, primarily in the form of ammonia emission, was reduced by 25 to 55% with an 8 to 55% reduction in P runoff loss. The highest reductions were obtained on a 1000-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 $88/cow for a 100-cow farm and $65/cow for the 1000-cow farm.