Atrazine Reduces the Critical Period of Weed Interference on Narrow Row Corn

Abstract

-The objective was to determine whether a change occurs in the critical period of weed interference prevention in narrow row corn with the use of atrazine and whether there is influence of the herbicide on crop yield components. The treatments consisted of periods without or with an initial weed control (0, 21, 35, 49, 63, 77, and 91 days after emergence), with or without application of atrazine in spikely post-emergence. The experiment was carried out in a 2 x 7 randomized blocks design (with and without weed control and seven periods with three replications). The use or not of atrazine was arranged in a split plot design. The most important weed species were Senecio brasiliensis, Urochloa plantaginea, Conyza bonariensis, Sida rhombifolia, and Solanum spp. Corn yield reduced by 15% and 18% with and without application of atrazine, respectively. The number of grains per spike and corn yield were negatively influenced by coexistence with weeds, while the number of rows per spike, the diameter and length of spike were not affected. Corn yield components were not affected by the use of atrazine. The critical period of weed interference prevention was 35 days without atrazine and 23 days with application of atrazine. There is a reduction of the critical period of weed interference prevention on narrow row corn by using atrazine, with no influence of the herbicide on crop yield.Keywords: herbicide, period of coexistence, Zea mays. (0, 21, 35, 49, 63, 77 RESUMO -O objetivo deste estudo foi verificar se ocorre alteração no período crítico de prevenção à interferência de plantas daninhas em milho adensado com o uso de atrazine e se há influência do herbicida sobre componentes de rendimento da cultura. Os tratamentos consistiram em períodos sem ou com controle inicial de plantas daninhas

Integrated Role of Row Spacing and Adjuvant to Reduce Herbicide Dose in Maize Under Semi-Arid Conditions

“…This decrease in density can be attributed to the fact that with reduced spacing maize crop established its canopy earlier and ultimately fewer weeds emerged. The results reinforced the findings of Tharp and Kells (2001), Shapiro and Wortmann (2006) and Padilha et al (2016), who reported that narrow row spacing reduced weed growth by increasing the competitive ability of maize plants with weeds as a result of fast and dense canopy development. These outcomes of this research are supported by Fanadzo et al (2010), who found that, despite crop density, narrow row offers more weed inhibition than wide rows.…”

“…These results are supported by Javaid et al (2012), who stated that an effective adjuvant activator enhances the penetration of the herbicide and increase weed control efficacy. More weed control efficiency at narrow row spacing might be due to more weed crop competition, which reduced weed growth and weed biomass, ultimately resulting in more weed control efficiency (Padilha et al, 2016). These results are reinforced by Maqbool et al (2006), who found that, despite crop density, narrow row spacing offers more weed inhibition than wide row spacing.…”

“…The effect of row spacing was also significant. Decreasing row spacing of maize resulted in significant reduction in weed density (Padilha et al, 2016). This decrease in density can be attributed to the fact that with reduced spacing maize crop established its canopy earlier and ultimately fewer weeds emerged.…”

“…However, effective weed control at reduced herbicide rates depends upon the type of herbicides being applied, type of adjuvant and characteristic of target weed species (Bunting et al, 2004). Narrow row spacing of maize negatively influenced weed growth and weed-crop competition by changing the critical period of weed interference with maize, reduced weed growth and more weed-crop competition enhanced the herbicide efficacy (Padilha et al, 2016;Khan et al, 2016). Reducing row spacing accelerates canopy establishment and results in improved radiation interception, growth, and yields of the crop (Andrade et al, 2002) and suppresses weed growth (Alford et al, 2004;Padilha et al, 2016) shifting the advantage in the favor of crops.…”