Soybean Growth and Development as Affected by Glyphosate and Postemergence Herbicide Tank Mixtures

Abstract

Field research was conducted to evaluate the effect of glyphosate [N‐(phosphonomethyl)glycine] and postemergence herbicide tank mixtures applied to soybean [Glycine max (L.) Merr.] at the V5 growth stage on growth, development, and grain yield of glyphosate‐resistant and nonresistant cultivars. Glyphosate at 840 g a.e. ha−1 did not affect vegetative growth, reproductive development, leaf area index (LAI), or grain yield of glyphosate‐resistant soybean compared with nontreated glyphosate‐resistant soybean. Soybean injury 21 d after treatment (DAT) was 14 to 18% when herbicide tank mixture treatments were applied. Soybean injury caused by postemergence herbicide tank mixtures resulted in delayed vegetative development when measured 7 DAT, delayed reproductive development at 20 and 80 DAT, reduced season‐long height of ‘Asgrow A1900’ and ‘Asgrow AG1901’, and reduced aboveground dry weight at 35 and 56 DAT compared with nontreated plants. Leaf area index was reduced by postemergence tank mixtures up to 52 DAT but was greater 70 and 80 DAT, depending on the cultivar. The ratio of red to far red light that reached the soil surface 28 DAT was dependent on cultivar and herbicide selection. Yield of soybean treated with herbicides other than glyphosate timed for weed control and disease suppression was reduced at least 200 and 130 kg ha−1 in 1997 and 1998, respectively, in the absence of weeds and disease.

Scientific Opinion on an application (EFSA‐GMO‐NL‐2005‐24) for the placing on the market of the herbicide tolerant genetically modified soybean 40‐3‐2 for cultivation under Regulation (EC) No 1829/2003 from Monsanto

“…In higher-tier field studies, performed in the USA in soils with naturally occurring Bradyrhizobium, Reddy (2004, 2007) reported transient negative effects on nitrogen metabolism in GMHT soybean due to exposure to glyphosate, but crop yield was unaffected. Other studies performed under a wide range of environments indicated no yield reductions due to glyphosate applications on glyphosate tolerant soybean, suggesting that soybean has the potential to recover from glyphosate stress (Delannay et al, 1995;Reddy and Whiting, 2000;Elmore et al, 2001a;Krausz and Young, 2001;Nelson and Renner, 2001;Reddy and Zablotowicz, 2003). Further, Powell et al (2009a) reported that nitrogen fixation was greater in GMHT soybean treated with glyphosate than in untreated plants when glyphosate was applied at the first trifoliate soybean growth stage.…”

Tracking photosynthetic injury of Paraquat-treated crop using chlorophyll fluorescence from hyperspectral data

“…Adcock et al [1990] used a ground-based radiometer to assess soybean injury from Paraquat and glyphosate and compared radiometer injury ratings with visual observations. Nelson and Renner [2001] reported an increase in the red (660 nm) to far-red light reflectance (740 nm) ratio in soybeans treated with lactofen when compared with glyphosate and bentazon treatments. Thelen et al [2004] found that both digital aerial imagery and ground-based optical remote sensing were effective in detecting lactofen and imazethapyr injuries on soybeans.…”

Response of Aryloxyalkanoate Dioxygenase-12 Transformed Soybean Yield Components to Postemergence 2,4-D

“…When 2,540 g ha 21 glyphosate was applied twice, yield was reduced by 11% in 1 yr of a 3-yr study (Zablotowicz and Reddy 2007), but yield reduction was attributed to reduced nitrogen fixation by symbiotic bacteria. However, other researchers found yield was not reduced from glyphosate treatments on glyphosate-resistant soybean (Delannay et al 1995;Elmore et al 2001a;Miller et al 2008;Nelson and Renner 2001). When glyphosate treatments of 800, 1,200, and 2,400 g ha 21 were applied to V2, V4, or V6, second-generation glyphosate-resistant soybean had a reduction in photosynthetic rate; nutrient accumulation; nodule production; leaf area; and root, shoot, and nodule biomass (Zobiole et al 2012).…”