630 Abstract Bedding materials may afect air quality in livestock facilities. Our objective in this study was to compare headspace concentrations of ammonia (NH 3 ), total reduced sulfdes (TRS), carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) when pine wood chips (Pinus spp.) and corn stover (Zea mays L.) were mixed in various ratios (0, 10, 20, 30, 40, 60, 80, and 100% pine chips) and used as bedding with manure. Air samples were collected from the headspace of laboratory-scaled bedded manure packs weekly for 42 d. Ammonia concentrations were highest for bedded packs containing 0, 10, and 20% pine chips (equivalent to 501.7, 502.3, and 502.3 mg m -3 , respectively) in the bedding mixture and were lowest when at least 80% pine chips were used as bedding (447.3 and 431.0 mg m -3 , respectively for 80 and 100% pine chip bedding). The highest NH 3 concentrations were observed at Day 28. The highest concentration of TRS was observed when 100% pine chips were used as bedding (11.4 µg m -3 ), with high concentrations occurring between Days 7 and 14, and again at Day 35. Greenhouse gases were largely unafected by bedding material but CH 4 and CO 2 concentrations increased as the bedded packs aged and N 2 O concentrations were highly variable throughout the incubation. We conclude that a mixture of bedding material that contains 30 to 40% pine chips may be the ideal combination to reduce both NH 3 and TRS emissions. All gas concentrations increased as the bedded packs aged, suggesting that frequent cleaning of facilities would improve air quality in the barn, regardless of bedding materials used. Ammonia, Total Reduced Sulfdes, and Greenhouse Gases of Pine Chip and Corn Stover Bedding Packs Mindy J. Spiehs,* Tami M. Brown-Brandl, David B. Parker, Daniel N. Miller, Elaine D. Berry, and James E. Wells L ivestock producers ofen use locally available by-products of cereal grain or lumber production as bedding in their facilities. Bedding material is usually selected based on availability and price. Recently, there has been increased construction of bedded confnement barns for feedlot cattle in the Upper Great Plains. Tis has created an increase in the demand for locally available crop residues (e.g., corn stover, soybean stover [Glycine max (L.) Merr.], wheat straw [Triticum aestivum L.]) that are used as bedding. Wood products may be a viable alternative. Wood contains many diferent organic chemicals that may infuence air quality (Nimenya et al., 2000; Miller et al., 2003; Misselbrook and Powell, 2005; Spiehs et al., 2014a). Spruce products were reported to inhibit urease-producing bacteria from converting ammonium (NH 4 ) in cattle urine to ammonia (NH 3 ; Nimenya et al., 2000). Others have shown that pine chip bedding has lower NH 3 emissions than the use of straw (Miller et al., 2003; Powell et al., 2008), newspaper, (Misselbrook and Powell, 2005), and recycled manure solids (Misselbrook and Powell, 2005; Powell et al., 2008). Tere is less information available about the efects of bed- ding material on greenhouse gases (GHG) and total reduced sulfdes (TRS) that potentially pollute the air, even though these gases are an environmental concern for livestock produc- ers. Tere were no diferences in NH 3 , nitrous oxide (N 2 O), and nitric oxide (NO) emissions from swine deep-bedded barns using wood shaving, straw, or sawdust bedding (Groenestein and Van Faassen, 1996). Jeppsson (2000) reported a signifcantly lower carbon dioxide (CO 2 ) emission rate from wood shavings than straw as bedding material in swine facilities. Use of sawdust litter in dairy barns decreased N 2 O emission rate, but increased CO 2 emission rate in a comparison with sand bedding (van Vliet et al., 2004). Methane (CH 4 ) and N 2 O total mean emissions were lower from feedyard manure containing straw compared to that without straw (Yamulki, 2006). Te author attributed the Abbreviations: AIC, Akaike Information Criteria; GHG, greenhouse gas; TRS, total reduced sulfdes. M.J. Spiehs, T.M. Brown-Brandl, E.D. Berry, and J. E. Wells, USDA-ARS Meat Animal Research Center, Clay Center, NE; D.B. Parker, USDA-ARS Conservation and Production Research Laboratory, Bushland, TX; D.N. Miller, USDA- Agroecosystems Management Research Unit, Lincoln, NE. USDA is an equal opportunity provider and employer. The mention of trade names of commercial products in this article is solely for the purpose of providing specifc information and does not imply recommendation or endorsement by the USDA. Assigned to Associate Editor Heidi Waldrip. Copyright © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. 5585 Guilford Rd., Madison, WI 53711 USA. All rights reserved. J. Environ. Qual. 45:630–637 (2016) doi:10.2134/jeq2015.09.0466 Received 15 Sep. 2015. Accepted 1 Dec. 2015. *Corresponding author (mindy.spiehs@ars.usda.gov). Journal of Environmental Quality ATMOSPHERIC POLLUTANTS AND TRACE GASES TECHNICAL REPORTS Core Ideas • Producers can use bedding material to help reduce gas emis- sions from livestock facilities. • Ammonia concentrations were highest when bedding con- tained 20% or less pine chips. • Total reduced sulfdes were highest when 100% pine chips were used in the bedding mixture. • Greenhouse gases were largely unafected by including pine chips in bedding mixtures. • Bedding materials of 30–40% pine and 60–70% corn may be ideal to reduce gas emissions. Published February 12, 2016