Interference Periods in Soybean Crop as Affected by Emergence Times of Weeds

Abstract

-Weeds emergence times modify competition with crops. Thus, the hypothesis was that the increase in weed emergence flow decreases the period prior to interference (PPI) in soybeans and increases the critical period of interference prevention (CPIP). The objective was to determine the PPI and the CPIP of weeds in soybean crops as affected by the preferred time of weeds emergence flow. Three experiments were conducted in the field in a randomized block design with four replications. The treatments were arranged in a factorial design with factor A consisting of coexistence or weed control in soybeans and factor B for eight periods (0, 7, 14, 21, 28, 35, 42 and 135 days after crop emergence (DAE)). The numbers of emerged plants and weed dry mass by genus and crop productivity were evaluated. The weed interference in culture during all the crop cycle reduces the soybean average yield 73, 94 and 89% in the first, second and third sowing times, respectively. Chemical control may be adopted at the end of PPI, which must be done at 14, 15 and 5 DAE crop, for the first, second, third times, respectively. The sowing in advance and intermediate time of recommendation increase the PPI in about 10 days, favoring the weed management in soybean crops. (0, 7, 14, 21, 28, 35, 42 Keywords: Glycine max, weed competition, crop yield losses. RESUMO -A época de emergência das plantas daninhas modifica a competição com as culturas. Assim, tem-se como hipótese que o aumento do fluxo de emergência de plantas daninhas diminui o período anterior à interferência (PAI) na soja, aumentando o período crítico de prevenção à interferência (PCPI). O objetivo foi determinar o PAI e o PCPI das plantas daninhas na cultura da soja, em função da época preferencial do fluxo de emergência de plantas daninhas. Realizaram-se três experimentos em campo, em delineamento experimental de blocos casualizados, com quatro repetições. Os tratamentos foram arranjados em esquema fatorial, sendo o fator A composto pela convivência ou controle de planta daninha na cultura da soja, e o fator B, por oito períodos

Selectivity of post-emergent herbicides for weed control in birdsfoot trefoil crops

“…Fomesafen also increased RDM, since its value was 16.9% higher than the one of the control. Increase in HEI and crop biomass ensures better establishment and competitive skills with weeds for environmental resources (Zandoná et al, 2018).…”

Cover plants as a suppression and increasing tool to hairy fleabane control

“…The application of pre-emergent herbicides within the resistance scenario is important to ensure the crop emergence in areas free from competition. Thus, a recent study showed that the emergence time of weeds has a distinct interference capacity in the soybean, with a critical control period ranging from 14 to 48 days after the crop emergence (Zandoná et al, 2018). On the other hand, cover plants reduced the height plants and promoting a better control efficiency.…”

New Formulation of Clethodim/Adjuvant at Control of Grass Weeds for Soybean Crops

“…The yield results demonstrated that poaceous weed infestation of the soybean crop prompted a 2064 kg ha -1 decline in seeds compared to the weed-free control (Figure 5). The weed interference in soybean during all the crop cycle reduces yield 73 to 94% in different sowing times (Zandona, et al, 2018). Considering a 5% tolerable yield decline, the soybean crop was negatively affected by weed infestation starting at 25 DAE (PAI) (Benedetti et al, 2009).…”

“…Competition of weeds with crops can generate irreversible losses, with no recovery of development or yield, even after the elimination of it (Agostinetto et al, 2014). Moreover, increase in the period when the crop remains with weed interference, greater the damage (Zandona et al, 2018).…”