Abstract
AbstractInformation about weed biology and weed population dynamics is critical for the development of efficient weed management programs. A field experiment was conducted in Fayetteville, AR, during 2014 and 2015 to examine the effects of Palmer amaranth (Amaranthus palmeriS. Watson) establishment time in relation to soybean [Glycine max(L.) Merr.] emergence and the effects ofA. palmeridistance from the soybean row on the weed’s height, biomass, seed production, and flowering time and on soybean yield. The establishment time factor, in weeks after crop emergence (WAE), was composed of six treatment levels (0, 1, 2, 4, 6, and 8 WAE), whereas the distance from the crop consisted of three treatment levels (0, 24, and 48 cm). Differences inA. palmeribiomass and seed production averaged across distance from the crop were found at 0 and 1 WAE in both years. Establishment time had a significant effect onA. palmeriseed production through greater biomass production and height increases at earlier dates.Amaranthus palmerithat was established with the crop (0 WAE) overtopped soybean at about 7 and 10 WAE in 2014 and 2015, respectively. Distance from the crop affectedA. palmeriheight, biomass, and seed production. The greater the distance from the crop, the higherA. palmeriheight, biomass, and seed production at 0 and 1 WAE compared with other dates (i.e., 2, 4, 6, and 8 WAE).Amaranthus palmeriestablishment time had a significant impact on soybean yield, but distance from the crop did not. The earlierA. palmeriinterfered with soybean (0 and 1 WAE), the greater the crop yield reduction; after that period no significant yield reductions were recorded compared with the rest of the weed establishment times. Knowledge ofA. palmeriresponse, especially at early stages of its life cycle, is important for designing efficient weed management strategies and cropping systems that can enhance crop competitiveness. Control ofA. palmeriwithin the first week after crop emergence or reduced distance between crop and weed are important factors for an effective implementation of weed management measures againstA. palmeriand reduced soybean yield losses due to weed interference.
Highlights
Weed exposure to diverse environmental stresses is exacerbated in agroecosystems, where weeds compete with crops for nutrients, water, light, and space (Korres 2005; Ramegowdaa and Senthil-Kumar 2015)
Amaranthus palmeri plants at 48 and 24 cm from the crop at 0, 1, 2, and 4 weeks after crop emergence (WAE) were significantly taller (P < 0.001 for 2014 and 2015) than A. palmeri plants growing adjacent to the soybean crop (Figure 3)
Amaranthus palmeri biomass production per plant was greater for A. palmeri plants established with the crop or at 1 WAE at a 48-cm distance from the crop compared with the biomass produced by those established at 2 WAE or later regardless the distance from the crop (Figure 4)
Summary
Weed exposure to diverse environmental stresses is exacerbated in agroecosystems, where weeds compete with crops for nutrients, water, light, and space (Korres 2005; Ramegowdaa and Senthil-Kumar 2015). Acquisition of these resources by the weeds intensifies, resulting in vigorous growth, increased seed production, and ease of weed population establishment, all of which have direct consequences on field operations, crop husbandry, and final crop yield (Korres 2005). The success of future weed management strategies targeting this weed will rely on an improved understanding of its biological, phenological, and reproductive characteristics and population dynamics (Puricelli et al 2002; Sellers et al 2003).
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