|Rotz, Clarence - Al|
Submitted to: Transactions of the ASAE
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/15/2006
Publication Date: 8/28/2006
Citation: Rotz, C.A., Oenema, J. 2006. Predicting management effects on ammonia emissions from dairy and beef farms. Transactions of the ASAE. 49(4):1139-1149. Interpretive Summary: The effect of farms on the environment has become a major social concern in many regions, particularly those with high concentrations of animal production. Environmental concerns include nutrient losses to the atmosphere, surface water bodies, and groundwater. The most recent concern is the volatilization of gases from animal facilities with the major emission being nitrogen in the form of ammonia. Ammonia emissions are of concern because ammonia in the atmosphere leads to the formation of small airborne particles with potential effects on human health. Atmospheric ammonia also contributes to over fertilization, acidification, and eutrophication of ecosystems. A number of management options can be used to improve nitrogen utilization in cattle production and thus reduce ammonia emission. Finding a cost-effective approach though, can be a challenge. All parts of the farm and their interactions must be considered when developing production practices to reduce emissions. This type of evaluation is best done through computer simulation. A processed-based model was developed to predict management effects on ammonia emissions from manure in the barn, during storage, following field application, and during grazing. This ammonia emission model was added to a farm simulation model forming a comprehensive tool for evaluating management effects on ammonia losses along with other aspects of farm performance and profit. Whole-farm simulations demonstrated that the use of a free stall barn, bottom-loaded slurry storage, and deep injection of manure into the soil reduced ammonia emissions by 35 to 50% compared to other commonly used dairy housing and manure handling systems while providing a small increase in farm profit.
Technical Abstract: Component models were developed to predict ammonia nitrogen losses from cattle manure in the barn, during storage, following field application, and during grazing. Ammonia loss in each phase was predicted using a mechanistic model for ammonia volatilized from the surface of an aqueous solution of ammonium where the ammonia 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 ammonia transport for the various loss pathways which predicted emissions similar to those reported in published studies. Model relationships were further evaluated to predict long-term average losses similar to those documented in previous work. 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 ammonia emissions by 35-50% compared to other commonly used dairy housing and manure handling systems in the northeastern US. 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.