Abstract
AbstractXtendFlex® technology from Bayer allows growers to apply glyphosate, glufosinate, and dicamba POST to cotton. Since the evolution and spread of glyphosate-resistant weed species, early POST applications with several modes of action have become common. However, crop injury potential from these applications warrants further examination. Field studies were conducted from 2015 to 2017 at two locations in Mississippi to evaluate XtendFlex® cotton injury from herbicide application. Herbicide applications were made to XtendFlex® cotton at the three- to six-leaf stage with herbicide combinations composed of two-, three-, and four-way combinations of glyphosate, glufosinate,S-metolachlor, and three formulations of dicamba. Data collection included visual estimations of injury, stand counts, cotton height, total mainstem nodes, and nodes above whiteflower at first bloom. Data collection at the end of the season included cotton height, total mainstem nodes, and nodes above cracked boll. Visual estimations of injury from herbicide applications were highest at 3 d following applications containing glufosinate +S-metolachlor (36% to 41% injury) and glufosinate +S-metolachlor in combination with dicamba + glyphosate (39% to 41% injury), regardless of the dicamba formulation. Crop injury decreased at each rating interval and dissipated by 28 d following applications (P = 0.3748). Height reductions were present at first bloom and at the end of the season (P < 0.0001), although cotton yield was unaffected (P = 0.2089), even when injury at 3 d after application was greater than 30%. Results indicate that growers may apply a variety of herbicide tank mixtures to XtendFlex® cotton and expect no yield penalty. Furthermore, if growers are concerned with cotton injury after herbicide applications, the use of glufosinate in combination withS-metolachlor should be approached with caution in XtendFlex® cotton.
Highlights
Over the past decade, the use and development of biotechnology-derived traits in row-crop agriculture has led to incredible advancements (Behrens et al 2007)
The herbicide combination was considered antagonistic if the expected cotton injury was greater than the observed injury (Ganie and Jhala 2017)
Trends were similar across years and locations regarding visible crop injury, effects on cotton growth and development, as well as cotton yield; data were pooled over years and locations
Summary
The use and development of biotechnology-derived traits in row-crop agriculture has led to incredible advancements (Behrens et al 2007). Similar combinations applied POST in dicamba-resistant soybean resulted in increased control of giant ragweed [Ambrosia trifida (L.)], Palmer amaranth, and waterhemp [Amaranthus tuberculatus (Moq.) J.D. Sauer] when compared to POST-applied treatments of glyphosate alone (Byker et al 2013; Johnson et al 2010; Vink et al 2012). Everman et al (2009) reported that the addition of S-metolachlor to POST glufosinate applications on cotton provided extended weed control and increased cotton lint yields. Clewis et al (2006) reported that the addition of S-metolachlor to glyphosate POST applications increased Palmer amaranth and other broadleaves control and increased cotton lint yield compared to glyphosate-alone applications. Few studies investigate EPOST applications on XtendFlex® cotton containing combinations of S-metolachlor, glufosinate, and glyphosate, and the resultant effects on visual estimations of injury, crop growth and development, and yield. This research was initiated to quantify the effect of herbicide tank-mixture combinations on visual estimations of injury, growth and development, and yield of XtendFlex® cotton
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