LAUSR

The Renewable Fuels Standard mandate provides enhanced opportunity for maize (Zea mays L.) stover use as a bioenergy feedstock. Living mulch (LM) offers a possible solution for the natural resources constraints associated with maize stover biomass harvest. A two-site-year study was conducted near Boone and Kanawha, IA, in both maize following maize (MM) and maize following soybean [Glycine max (L.) Merr.] (SM) sequences to evaluate the impact of established and chemically suppressed Kentucky bluegrass (Poa pratensis L.) ‘Ridgeline’, ‘Wild Horse’, ‘Oasis’, and ‘Mallard’ blend and creeping red fescue (Festuca rubra L.) ‘Boreal’ as LM on three maize hybrids (population sensitive, population insensitive, and yield stable). Maize grain yield for the no LM treatments in the MM and SM sequences was 12.0 and 13.2 Mg ha−1, respectively, at Boone and 12.8 and 14.8 Mg ha−1, respectively, at Kanawha, 23 to 73% greater than the LM treatment. Ethanol yield (L ha−1) was 12 to 119% greater, protein concentration was £9% greater, and starch concentration was £1% lower in the no LM treatment maize than in LM treatment maize. Maize hybrid by cover interaction was significant for parameters including total aboveground biomass and protein concentration at Boone, with inconsistent maize hybrid responses to the LM system. Stover yield, stover quality, stover C and N, leaf area index, maize plant density, maize maturity, and sequence year in the MM sequence were also evaluated. Results emphasize the need for maize hybrid and LM system compatibility, as well as effective LM suppression techniques. C.A. Bartel*, C. Banik, A.W. Lenssen, K.J. Moore, D.A. Laird, S.A. Archontoulis, and K.R. Lamkey, Dep. of Agronomy, Iowa State Univ., Agronomy Hall, 716 Farmhouse Ln., Ames, IA 50011-1051. Received 12 Apr. 2017. Accepted 6 Aug. 2017. *Corresponding author (cabartel@ iastate.edu). Assigned to Associate Editor Jeffrey Coulter. Abbreviations: ADF, acid detergent fiber; ADL, acid detergent lignin; a.e., acid equivalent; CF, creeping red fescue; GDD, growing degree days; HI, harvest index; KB, Kentucky bluegrass; LAI, leaf area index; LM, living mulch; MM, maize following maize; NDF, neutral detergent fiber; SM, maize following soybean. Published in Crop Sci. 57:3273–3290 (2017). doi: 10.2135/cropsci2017.04.0232 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. Published online October 13, 2017