Yield, germination and herbicide residue in seeds of preharvest desiccated wheat

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.

Physiological attributes of Enlist E3™ soybean seed submitted to herbicides application

“…The highest GSI values in this study were achieved with 2,4-D choline + glyphosate and glufosinate herbicides, which corroborates studies using the glufosinate and 2,4-D + glyphosate desiccants in wheat (Perboni et al, 2018). The ammonium glufosinate herbicide can be used for the purpose of desiccant in the pre-harvest of soybean crops (Guimarães et al, 2012).…”

“…Although selective to crops, herbicide application can generate stresses, which are characterized as any negative effect on the growth and normal development of plant species (Agostinetto et al, 2016). Changes in the metabolic pathways caused by herbicides application can lead to reduced growth and development of plants and, consequently, reduce the mass of seeds, affecting their physiological quality (Perboni et al, 2018).…”

Pre-harvest herbicide application reduces the Italian ryegrass seed viability

“…Herbicides application at prespike and anthesis stages caused strong reduction in germination (decreases greater than 98%), except for iodosulfuron-methyl applied after the anthesis stage, with the germination of 21% (Table 2). In wheat plants, recent studies have been reporting the negative effects on seed germination after paraquat and glyphosate application due to the oxidative damage of membranes caused when herbicides are applied in the pre-harvest (Bellé et al 2014, Perboni et al 2018. The increase of dead seeds occurred for all herbicides applied in the pre-spike and anthesis stages, with decreases greater than 98%, except for iodosulfuron-methyl applied at anthesis in which dead seeds were only 76% (Table 2).…”

“…Herbicide burndown in wheat pre-harvest reduced seed weight and hectoliter mass, affecting the seedling establishment (Krenchinski et al 2017). However, seed weight reduction depends on the phenological stage, with lower effects for herbicide application after the grain filling (Perboni et al 2018). Lower germination percentages were found for all herbicides applied, regardless of the phenological stages evaluated compared to the control, in which the germination was of 89% (Table 2).…”

“…The inhibition of physiological processes caused by herbicides can affect seed formation, resulting in lower physiologic quality (Campos et al 2012). For example, paraquat and glyphosate application before the complete wheat seed formation can cause lower germination and reduce the vigor (Perboni et al 2018). In contrast, non-viable seeds production in Italian ryegrass after herbicide application depends on the plant phenological stages to provide higher effects on physiological quality.…”