NE132: Environmental and Economic Impacts of Nutrient Management on Dairy Forage Systems
Statement of Issues and Justification
Dairy farming in the U.S. is under increasing pressure by two major factors. First factor is the decline of milk prices. Milk prices are moving toward a world market price that is causing a continuing trend toward larger dairy farms concentrated in certain geographic locations. The second factor is the relatively recent environmental concern for dairy farm nutrient losses The cost of managing manure nutrients is being assumed by the farm owner. These two factors are colliding on traditional dairy production areas in ways that are having significant negative impacts on rural families and communities.Integrated research and technology transfer programs are needed discover how to better help dairy farmers manage their farms in a cost effective and environmentally acceptable manner, and in ways that comply with newly imposed farming regulations.
Recently, attention has focused on animal production systems as non-point sources of pollution affecting the quality of streams, estuaries, and ground water resources. In particular, nitrogen and phosphorus may contaminate water after application of manure or chemical fertilizer to soils (Morse, 1995). These nutrients may be lost from farms with runoff water after a rainfall (Baker and Senft, 1993), or nitrogen may leach through soils into ground water (Joshi et al., 1994). Some nitrogen becomes volatilized as ammonia from manure or soils, and eventually contributes to acid rain that endangers forests and water bodies (Luebs et al., 1973). Some nitrogen may be lost from the farm by conversion to atmospheric N2 (denitrification), but the majority is lost to water resources.
Agricultural practices have become more intensive to provide for the nutritional needs of an increasing human population and as a response to economic pressures on individual farms (de Wit, 1992). Higher production levels are possible on farms through the use of chemically fixed fertilizer and feeds imported to farms from other regions. However, such practices also increase the potential for nutrient losses from the farm.
Several technology and incentive programs are aimed at reducing the risk of environmental damage from animal agriculture while maintaining farm productivity. However, in order to better direct these resources, there is a need for routine assessment of which farm management practices are most effective on specific farms. There is a need for the development of farm management decision support tools to help producers and their consultants identify the most appropriate strategies for managing nutrients on a farm by farm basis. In addition, there is a need to collect and analyze data in the field, so as to identify the most appropriate technology transfer programs to address the problems associated with nutrient pollution in a cost effective manner.
Because the environmental impact of a farm management decision depends on farm characteristics (e.g., soil capacity) and other management selections (e.g., crop rotations, tillage, manure storage), the only way to calculate the benefit of a farm practice is to model the changes in nutrient flows through the entire system. Development of integrated mathematical models enables calculation of the environmental benefit from one or more management or infrastructure changes in any management subsystem (crops, soils, feed, animal). The development of such an integrated understanding of the farm nutrient cycle requires participation by scientists in a number of diverse disciplines.
The NE-132 project has brought together a broad range of disciplines and led to the development of quantitative models, the Dairy Forage System Model (DAFOSYM) and the Dairy Nutrient Planner (DNP). These models integrate years of collaborative research and enable an enhanced understanding of nutrient flows in the farm system. However, DAFOSYM is intended for research and teaching purposes rather than extension, and the DNP was targeted for a specific geographic region (Pennsylvania) and still requires further development. These models need to be further evaluated and adapted to address the immediate needs in the field across the nation related to nutrient management on dairy farms. In the new project, models that were previously developed will be used and evaluated under diverse farm conditions to identify improved strategies for management of nutrients on farms. Models will be developed for on-farm use in various regions of the U.S.
To advance whole-farm model evaluation and application, a coordinated effort is needed at several levels. First, field studies of nutrient dynamics and cropping systems are needed to calibrate predictions for different geographic locations and to evaluate model components. Second, model refinements and software development are needed to enable use of the models on individual farms throughout the U.S. Finally, model prediction capacity must be expanded to more accurately partition nutrient losses into those from volatilization, leaching, runoff and denitrification, and consequences of alternative feeding or crop management systems must be expanded.
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