Characterizing genotype × Management interactions on soybean seed yield

Increased soybean [Glycine max (L.) Merr. ] commodity prices in recent years have generated interest in high-input systems to increase yield. The objective of this study was to evaluate the effects of current, high-yielding cultivars under highand low-input systems on soybean yield and yield components. Research trials were conducted at 19 locations spanning nine states from 2012 to 2014. At each location, six highyielding cultivars were grown under three input systems: (i) standard practice (SP, current recommended practices), (ii) high-input treatment consisting of a seed treatment fungicide, insecticide, nematistat, inoculant, and lipo-chitooligosaccharide (LCO); soil-applied N fertilizer; foliar LCO, fertilizer, antioxidant, fungicide and insecticide (SOYA), and (iii) SOYA minus foliar fungicide (SOYA-FF). An individual site-year yield analysis found only 3 of 53 (5.7%) siteyears examined had a significant cultivar × input system interaction, suggesting cultivar selection and input system decisions can remain independent. Across all site-years, the SOYA and SOYA-FF treatments yielded 231 (5.5%) and 147 kg ha–1 (3.5%) more than the SP, and input system differences were found among maturity groups. Yield component measurements (seeds m–2, seed mass, early-season and final plant stand, pods plant–1, and seeds pod–1) indicated positive yield responses were due to increased seeds m–2 and seed mass. While both high-input systems increased yield on average, grower return on investment (ROI) would be negative given today’s commodity prices. These results further support the use of integrated pest management principles for making input decisions instead of using prophylactic applications to maximize soybean yield and profitability. D.A. Marburger and S.P. Conley, Dep. of Agronomy, Univ. of Wisconsin-Madison, 1575 Linden Drive, Madison, WI 53706; B.J. Haverkamp and K.L. Roozeboom, Dep. of Agronomy, Kansas State Univ., 1712 Claflin Road, Manhattan, KS 66506; R.G. Laurenz and K.D. Thelen, Dep. of Plant, Soil, and Microbial Sciences, Michigan State Univ., 1066 Bogue Street, East Lansing, MI 48824; J.M. Orlowski, Delta Research and Extension Center, Mississippi State Univ., P.O. Box 197, Stoneville, MS 38776; E. W. Wilson and S.L. Naeve, Dep. of Agronomy and Plant Genetics, Univ. of Minnesota-Twin Cities, 1991 Upper Buford Circle, St. Paul, MN 55108; S.N. Casteel, Dep. of Agronomy, Purdue Univ., 915 West State Street, West Lafayette, IN 47907; C.D. Lee, Dep. of Plant and Soil Sciences, Univ. of Kentucky, 1405 Veterans Drive, Lexington, KY 40546; E.D. Nafziger, Dep. of Crop Sciences, Univ. of Illinois at Urbana-Champaign, 1102 South Goodwin Avenue, Urbana, IL 61801; and W.J. Ross, Dep. of Crop, Soil, and Environmental Sciences, Univ. of Arkansas, P.O. Box 391, Little Rock, AR 72203. Received 25 Sept. 2015. Accepted 5 Dec. 2015. *Corresponding author (dmarburger@wisc.edu). Abbreviations: IPM, integrated pest management; LCO, lipo-chitooligosaccharide; MG, maturity group; ROI, return on investment; SOYA, high-input treatment consisting of university recommendations for fertilizer and herbicide programs; seed treatment fungicide, insecticide, nematistat, inoculant, and lipo-chitooligosaccharide; soil-applied nitrogen fertilizer; foliar lipo-chitooligosaccharide, fertilizer, antioxidant, fungicide, and insecticide; SOYA-FF, SOYA minus foliar fungicide; SP, standard practice (current university recommendations for fertilizer and herbicide programs). Published in Crop Sci. 56:786–796 (2016). doi: 10.2135/cropsci2015.09. 0576 © Crop Science Society of America 5585 Guilford Rd., Madison, WI 53711 USA This is an open access article distributed under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Published February 5, 2016