Corn and Barnyardgrass Competition as Influenced by Relative Time of Weed Emergence and Corn Hybrid

Abstract

Barnyardgrass [Echinochloa crus‐galli (L.) Beauv.] is a weed with global impacts on corn (Zea mays L.) production. Field experiments were conducted in western Greece in 2008 and 2009 to determine the influence of barnyardgrass emergence time and corn hybrid on corn yield and barnyardgrass growth and fecundity. Barnyardgrass was uniformly seeded at dates such that it emerged concurrently with corn and at the two, four, and six‐leaf stage of corn (VE, V2, V4, and V6 growth stages, respectively). Barnyardgrass biomass, tillers, canopy area and seed production were significantly affected by the date of barnyardgrass emergence. Barnyardgrass plants emerging with corn produced 1010 to 1305 seeds per plant compared to only 112 to 240 seeds from plants emerging after the V4 growth stage. Maximum corn grain yield loss ranged from 24 to 34% for early emerging barnyardgrass, and <9% yield loss occurred from barnyardgrass seedlings emerging later than the V4 growth stage. Corn hybrids with rapid initial growth rate (such as ‘Factor’ and ‘Dracma’) were more competitive than the other hybrids. The results of this study are essential in the development of an integrated weed management strategy for corn. Findings suggest that despite the high competitiveness of barnyardgrass, careful selection of a competitive corn hybrid and control of barnyardgrass through at least the V2 to V4 growth stage could dramatically reduce grain yield loss and weed seed production.