|Powell, J mark|
Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/15/2005
Publication Date: 6/5/2006
Citation: Powell, J.M., Misselbrook, T., Broderick, G.A. 2006. Abating ammonia emissions from dairy barns through feed, herd and bedding management. In: Proceedings of Workshop on Agricultural Air Quality: State of Science, June 5-8, 2006, Raleigh, North Carolina. p. 1006-1010. Interpretive Summary:
Technical Abstract: Dairy farms are thought to emit large amounts of ammonia and therefore contribute to nitrogen (N) fertilization of natural ecosystems and provide precursors for particulates that adversely affect visibility and human health. Approximately 20 to 35% of the N (crude protein, CP) fed to a dairy cow is secreted in milk; the remainder is excreted in manure, a portion of which can be lost rapidly as ammonia. One of the most reliable approaches to reducing ammonia emissions per unit of milk produced is to increase the level of milk production per cow. On Wisconsin dairy farms, milk production and feed N use efficiency are highest on farms that use total mixed rations (TMR), that balance rations four times per year, and milk thrice daily. These practices put more feed nutrients into product (milk), and less into manure. When recommended protein levels are fed to dairy cows, manure N is excreted approximately equally in urine and feces. Feeding N to dairy cows in excess of their requirements dramatically increases urine N excretions, and after land application, ammonia emissions. For example, in a laboratory trial, fresh and stored slurry from a low CP (13.6%) diet had less than one-half the ammonia loss than slurries from the high CP (19.4%) diet. Fresh slurry derived from birdsfoot trefoil, high tannin (BF-T-High) diets had less ammonia loss than slurry from alfalfa or birdsfoot trefoil, low tannin (BF-T-Low) diets. Stored slurry from BF-T-High and -Low diets had less ammonia loss than slurry derived from alfalfa. Our research is showing that bedding material can also influence the magnitude of ammonia emissions. The physical characteristics of bedding are of more importance than their chemical characteristics in determining ammonia emissions from applied urine and feces. Preliminary results from in-barn trials showed that ammonia loss from composted manure solids was greater than from chopped straw and pine shavings; and that ammonia emissions are 20 to 55% greater during the summer than during the winter. Reducing ammonia N losses from dairy farms and making greater use of conserved manure N will quickly make economic sense. As the price of natural gas and fertilizers continue to skyrocket, the fertilizer N value of manure, and therefore the conservation of the ammonia N contained in manure, will become more important. Reducing volatile N losses would not only conserve manure N available for field applications, but also reduce the amount of carbon dioxide, a greenhouse gas, that is generated in making fertilizer N.