Abstract
Abstract: The goals of this study were to evaluate herbicide application rates at different timings for preharvest desiccation of wheat (Trial 1), as well as to evaluate the effect of the timing of herbicide desiccation at preharvest and harvest timing (Trial 2) on yield, germination, and herbicide residue in wheat seed. In Trial 1, treatments consisted of two application rates of glufosinate, glyphosate, paraquat, or paraquat+diuron and a control without application; application time periods were in the milk grain to early dough stage, soft dough to hard dough stage, and hard dough stage. In Trial 2, treatments consisted of different application time periods (milk grain to early dough stage, and soft dough to hard dough stage), different herbicides (glufosinate, 2,4-D+glyphosate, and untreated control), and different harvest times (5, 10 and 15 days after herbicide application). One thousand seeds weight, yield, first and final germination count, and herbicide residue on seeds were evaluated. Preharvest desiccation with paraquat, glufosinate, and 2,4-D+glyphosate at the milk grain to early dough stage reduces wheat yield. Regardless of the herbicide and application rate, application in the milk grain to early dough stage and soft dough to hard dough stage provides greater germination of wheat seeds, except at the lower dose of paraquat. Systemic herbicides accumulate more in wheat seeds.
Highlights
Cultivation of super early maturing soybean cultivars in Southern Brazil mainly due to climate and disease management issues, has shifted sowing to an earlier time and, pushed wheat harvest, the main winter crop in this region, to an earlier time (Bianchi et al, 2011)
Application of paraquat in the milk grain to soft dough stage reduced wheat yield compared to application of glufosinate, glyphosate, and paraquat+diuron
Preharvest desiccation, regardless of the herbicide and application rate, performed in the milk grain to soft dough stage and soft dough to hard dough stage leads to greater germination of wheat seeds, except for paraquat at the low application rate
Summary
Cultivation of super early maturing soybean cultivars in Southern Brazil mainly due to climate and disease management issues, has shifted sowing to an earlier time and, pushed wheat harvest, the main winter crop in this region, to an earlier time (Bianchi et al, 2011). Nonselective herbicides have been applied to different crops to promote an early harvest and reduce interference from weeds. The application of desiccant herbicides accelerates the process of water loss from plants and from seeds, which moves up harvest time and reduces the period of prolonged exposure to factors that bring about deterioration after physiological maturity (Griffin et al, 2010). Preharvest desiccants should be applied at the right time because applications made before the crops reach physiological maturity interfere with grain filling and seed quality (Jaskulski and Jaskulska, 2014). Herbicides used during desiccation in preharvest can accumulate in seeds, reducing their vigor and germination (Jaskulski and Jaskulska, 2014; Subedi et al, 2017)
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