Yield Responses to Planting Density for US Modern Corn Hybrids: A Synthesis-Analysis

Identifying an optimal plant density is a critical management decision for corn (Zea mays L.) production. The main objectives of this study were to: (i) investigate the grain yield responses to plant density (yield-density relationship), (ii) identify best fitted yield-density response curves, and (iii) explore genotype (G) x environment (E) interaction effect on yield-density response models. Analysis was conducted on meta-data (124,374 observations) gathered from 22 US states and 2 Canadian provinces, diverse sites (E), for years from 2000-2014 on multiple hybrids (G). Yield data were further grouped into four yield environments (low [LY], <7 Mg ha(-1); medium [MY], 7-10 Mg ha(-1); high [HY], 10-13 Mg ha(-1); and very high [VHY], > 13 Mg ha(-1) yielding groups). Primary outcomes from this analysis were: (1) strong G x E interaction; (2) a quadratic model best fitted yield-density relationship; (3) four contrasting yield-density responses identified as dominant in each yield productivity environment, i.e., a declining, a constant, an increasing, and ever-increasing type; (4) the yield productivity environment varied for the different corn comparative relative maturity (CRM) groups, i.e., the LY environment for long-maturing hybrids matched with a MY or HY environment for short maturing hybrids; and (5) maximum yielding plant density (MYPD) was lower but maximum yield was greater for long-versus short-maturing hybrids. In summary, optimal plant density should be decided based on detailed G x E analysis of production conditions that include factors such as CRM, yield productivity environment (weather-soil x management practices), and site information.