185 Abstract Long-term application of feedlot manure to cropland may infuence soil mesofauna. These organisms afect the health, structure, and fertility of soils, organic matter decomposition, and crop growth. The objective was to study the long-term (16–17 yr) infuence of feedlot manure type and bedding on soil mesofauna over 2 yr (2014–2015). Stockpiled or composted feedlot manure with straw (ST) or wood-chip (WD) bedding (plus unamended control) was annually applied (13 Mg ha −1 dry wt.) to an irrigated clay loam soil with continuous barley (Hordeum vulgare L.). Intact cores were taken from surface (0–5 cm) soil in the fall, and the densities of Acari (mites) suborders and Collembola (springtails) families were determined. Manure type had no signifcant (P > 0.05) efect on soil mesofauna density. In contrast, there was a signifcant two- to sixfold increase in density with WD- compared with ST-amended soils of total Acari in 2014 and 2015, as well as total Collembola, total Acari and Collembola, oribatid mites, and entomobryid springtails in 2014. The bedding efect was attributed to signifcantly greater soil water content and lower bulk density for WD than ST. Density of soil mesofauna was not signifcantly greater in amended soils than in unamended soils. A shift by feedlot producers from stockpiled to composted feedlot manure application should have no efect on soil mesofauna density, whereas a shift from ST to WD bedding may increase the density of certain soil mesofauna, which may have a benefcial efect on soil. Response of Soil Mesofauna to Long-Term Application of Feedlot Manure on Irrigated Cropland Jim J. Miller,* Jef P. Battigelli, Bruce W. Beasley, and Craig F. Drury S oil mesofauna such as Acari (mites) and Collembola (springtails) in belowground ecosystems can enhance microbial activity, accelerate and regulate organic matter decomposition rates, increase soil respiration and nutrient min- eralization, mediate transport of microbes throughout the soil, improve biological control and suppression of soil-borne diseases and pests, increase sequestering of carbon (C) and other miner- als, improve soil structure, and increase plant growth (Neher and Barbercheck, 1999; Scheu et al., 1999; Filser, 2002; Behan- Pelletier, 2003; Phelan, 2004). Long-term application of manure to cropland may infuence the density and species diversity of soil mesofauna in soil. Increased soil organic matter from manure application may infuence soil mesofauna directly by increasing the quantity and modifying the quality of organic matter and indi- rectly by changing the soil physical environment (Phelan, 2004). Most studies have reported that manure application generally increased densities of soil mesofauna (Weil and Kroontje, 1979; Andrén and Lagerlöf, 1983; Pimental and Warneke, 1989; Sokolowska and Seniczak, 2005; Jiang et al., 2015), Acari (Minor and Norton, 2004; Booher et al., 2012; Moradi et al., 2013), or Collembola (Curry and Purvis, 1982; Bandyopadhyaya et al., 2002; Muturi et al., 2011). Other researchers have reported that manure application reduced the density of soil Acari (Kruczyńska and Seniczak, 2010; Cao et al., 2011) or Collembola (Ngosong et al., 2009) had inconsistent efects (Fratello et al., 1989) or had no efect (Kautz and Ellmer, 2006). Still, other researchers stated that soil mesofauna density was dependent on application rate of liquid manure amendments, with studies reporting either a negative (Domek-Chruścicka and Seniczak, 2005; Graczyk and Wasińska-Graczyk, 2008) or a positive (Wasińska-Graczyk and Graczyk, 2009) efect at higher application rates. A number of studies evaluating the response of soil meso- fauna communities have been conducted using farmyard manure (Curry and Purvis, 1982; Andrén and Lagerlöf, 1983; Lootsma and Scholte, 1998; Bandyopadhyaya et al., 2002; Kautz and Ellmer, 2006), solid (Moradi et al., 2013) or liquid cattle manure (Sokolowska and Seniczak, 2005; Graczyk and Wasińska- Graczyk, 2008; Kruczyńska and Seniczak, 2010), sheep manure (Jiang et al., 2015), liquid pig manure (Domek-Chruścicka and Seniczak, 2005; Wasińska-Graczyk and Graczyk, 2009), poultry and sheep manure (Fratello et al., 1989), beef cattle and swine Abbreviations: CM, composted feedlot manure; FM, fresh manure; SM, stockpiled manure; ST, straw; WD, woodchip. J.J. Miller, B.W. Beasley, Agriculture and Agri-Food Canada, 5403 1st Ave. South, Lethbridge, AB T1J 4B1; J.P. Battigelli, Dep. of Renewable Resources, Univ. of Alberta, Edmonton, AB T6G 2E3; C.F. Drury, Agriculture and Agri-Food Canada, 2585 County Rd. 20, Harrow, ON NOR 1GO. Assigned to Associate Editor Kari Dunfeld. 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. 46:185–192 (2017) doi:10.2134/jeq2016.08.0318 Received 29 Aug. 2016. Accepted 5 Dec. 2016. *Corresponding author (jim.miller@agr.gc.ca). Journal of Environmental Quality WASTE MANAGEMENT TECHNICAL REPORTS Core Ideas • Manure type had no infuence on soil mesofauna. • Bedding material had a signifcant infuence on soil mesofauna. • Soil mesofauna densities were greater for wood- than straw- amended soils. • Bedding efect was due to greater soil water content and lower bulk density. • Soil mesofauna density was not greater for amended than un- amended soils. Published January 12, 2017