Environmental and economic comparisons of manure application methods in farming systems

Authors: Rotz, Clarence - Al; Kleinman, Peter; Dell, Curtis; Veith, Tameria - Tamie; BEEGLE, DOUGLAS - Pennsylvania State University

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/2010
Publication Date: 2/23/2011
Citation: Rotz, C.A., Kleinman, P.J.A., Dell, C.J., Veith, T.L., Beegle, D. 2011. Environmental and economic comparisons of manure application methods in farming systems. Journal of Environmental Quality. 40:438-448.

Interpretive Summary: Proper recycling of manure nutrients is a major issue on livestock farms in the U.S. and other developed countries. Animal manure provides nutrient rich organic matter that can serve as a valuable fertilizer resource for crop production. In a well managed production system, manure nutrients are returned to the soil where they are used to produce feed crops for animal production. The problem in this recycling of nutrients is that losses occur, and these losses can adversely affect the environment. Nutrient losses of greatest concern are gaseous emission of ammonia, nitrate leaching to ground water, and surface runoff of phosphorus. Farm management strategies are desired to minimize these nutrient losses to the environment and maximize their use in crop production without adversely affecting farm profitability. Computer simulation of farms, supported by field research, was used to evaluate and compare the performance, environmental impact, and economics of alternative manure application methods. Simulation results showed that reductions in ammonia emission and phosphorus runoff losses were obtained through improved incorporation of manure. Use of a shallow disk injection device for applying manure below the soil surface generally provided the lowest nutrient losses without substantially reducing farm profitability. In some farming systems, the improvement in crop production provided through reduced nutrient losses improved farm profit. Use of band application of manure along with soil aeration provided less environmental benefit, and the increased costs of production were generally greater than the economic benefit received. This information will help animal producers choose manure application equipment that reduces their impact on the environment while maintaining farm profitability.

Technical Abstract: Alternative methods for applying livestock manure to no-till soils involve environmental and economic trade-offs. A process-level farm simulation model (Integrated Farm System Model) was used to evaluate methods for applying liquid dairy (Bos taurus L.) and swine (Sus scrofa L.) manure including no application, broadcast spreading with and without incorporation by tillage, band application with soil aeration, and shallow disk injection. The model predicted ammonia emissions, nitrate leaching, and phosphorus (P) runoff losses similar to those measured over 4 years of field trials. Each application method was simulated over 25 years of weather on three Pennsylvania farms. On a swine and cow-calf beef operation under grass production, shallow disk injection increased profitability by $578/year while reducing ammonia nitrogen (N) and soluble P losses by 48 and 57%, respectively. On a corn and grass-based grazing dairy farm, shallow disk injection reduced ammonia loss by 21% and soluble P loss by 76% with little impact on farm profit. On both farms, incorporation by tillage and band application with aeration provided less environmental benefit, and the increased costs of production were greater than the economic benefit received through improved crop production. On a large corn and alfalfa based dairy farm where manure nutrients were available in excess, incorporation methods were not economically beneficial, but they provided environmental benefits with a relatively low annual net cost of $13 to $18/cow. In all farming systems, shallow disk injection of manure provided the greatest environmental benefit at the least cost or greatest profit for the producer.