Interactions Between Soybean (Glycine max) Cultivars and Selected Weeds

Abstract

Competition of weeds was characterized by determining the distance down the soybean row that a weed affects soybean biomass and yield. Field studies were conducted for 2 yr to compare competitive effects of common cocklebur, johnsongrass, Palmer amaranth, sicklepod, and tall morningglory on ‘Forrest’ and ‘Centennial’ soybeans. The weeds did not significantly reduce soybean biomass for 6 weeks after emergence. Palmer amaranth, common cocklebur, and tall morningglory had the greatest biomass by 6 weeks after emergence. However, only competition from common cocklebur and Palmer amaranth measurably reduced soybean biomass during the growing season. Biomass of Forrest and Centennial soybeans was reduced when these cultivars were growing within 12.5 and 50 cm of common cocklebur, respectively. Johnsongrass, sicklepod, and tall morningglory grew more slowly than the other weeds and had no measurable competitive effects on soybean biomass. Soybean competition reduced biomass of all weeds 90 to 97%. Soybean cultivar influenced the level and duration of competitiveness depending on the weed species present. Biomass of both soybean cultivars was reduced when they were growing within 50 cm of Palmer amaranth. Soybean seed yield was reduced when soybeans were growing within 25 cm of common cocklebur and Palmer amaranth and also when they were growing within 12.5 cm of tall morningglory. Sicklepod had no effect on soybean seed yield.

Effect of Row Spacing, Seeding Rate, and Herbicide Program in Glufosinate-Resistant Soybean on Palmer Amaranth Management

“…The 45-cm row spacing had greater grain yield (3,070 kg ha À1 ) than both the 19-and 90-cm spacings (2,100 and 2,120 kg ha À1 , respectively). Yield reductions up to 79% from Palmer amaranth have previously been reported (Bensch et al 2003;Klingaman and Oliver 1994;Monks and Oliver 1988); however, with the occurrence of GR Palmer amaranth, producers have experienced complete crop loss in some fields (personal communication; Arkansas Soybean Producers).…”

“…Palmer amaranth's prolific seed production (! 250,000 seed per female plant [Keeley et al 1987;Scott and Smith 2011;Sellers et al 2003]), extended emergence period (early April until the first killing frost [DeVore et al 2013;Jha and Norsworthy 2009]), and rapid erect growth (Klingaman and Oliver 1994;Monks and Oliver 1988;Norsworthy et al 2008b) make it one of the most troublesome weeds in crop production.…”

Palmer Amaranth and Large Crabgrass Growth with Plasticulture-Grown Bell Pepper

“…The crop benefits from drip line irrigation and fertigation beneath the plastic; however, weeds growing in the openings made for the crop also benefit. This close proximity of weeds to the crops in plasticulture maximizes interference, and in turn, weed growth and development can also be influenced (Monks and Oliver 1988;Pike et al 1990). …”

Comparative growth of Palmer amaranth (Amaranthus palmeri) accessions

“…Amaranthus spp. infestations increased in frequency and severity from 1974 to 1995 according to surveys of troublesome weeds (Webster and Coble 1997) and have caused yield reductions in major crops including corn (Zea mays L.) (Massinga et al 2001), cotton (Gossypium hirsutum L.) (Rowland et al 1999;Smith et al 2000), grain sorghum [Sorghum bicolor (L.) Moench] (Moore et al 2004), and soybean [Glycine max (L.) Merr] (Klingaman and Oliver 1994;Monks and Oliver 1988). Increases in Amaranthus infestations have been attributed to widespread adoption of reduced-tillage systems, decreased reliance on soil-applied residual herbicides, increased incidence of herbicide resistance, variable susceptibility to postemergence herbicides among Amaranthus spp., and species shifts in some areas of the country (Horak and Loughlin 2000;Horak and Peterson 1995;Mayo et al 1995;Sweat et al 1998).…”