Efeito do glifosato no desenvolvimento inicial do feijão-caupi

Abstract

Cowpea (Vigna unguiculata) is of significant socio-economic importance in the North and Northeast regions of Brazil, notable for its climatic adaptation and high nutritional value. However, the interference of weeds can compromise productivity, especially when they emerge before or simultaneously with the crop. Herbicides are strategic tools to mitigate such losses, with efficacy dependent on the developmental stage of both the crop and the weeds. This study aimed to evaluate the effect of glyphosate herbicide on the early development of cowpea, focusing on emergence, vegetative growth, and phytotoxicity. The research was conducted in experimental plots at the Department of Phytotechnology, Federal University of Ceará, using the BRS Aracê cultivar, 2021 crop. A randomized block design was applied with five treatments: control (water application only), glyphosate application at sowing (0 DAS), and applications at 2, 4, and 6 days after sowing (DAS). Variables analyzed included emergence percentage (%E), emergence velocity index (IVE), mean emergence time (TME), shoot (CPA) and root (CPR) lengths, fresh and dry biomass of shoots (MFPA, MSPA) and roots (MFSR, MSSR). Phytotoxicity was assessed using a visual symptom scale. Data were analyzed using ANOVA and Tukey’s test at 5% probability, using R Studio software. Results indicated that glyphosate application at sowing (0 DAS) significantly impaired seed germination, reducing %E and IVE. Shoot growth was adversely affected, particularly with the 4 DAS treatment, which resulted in shorter length and lower biomass. Root growth was not significantly affected. Phytotoxicity symptoms, such as chlorosis, necrosis, and epinasty, were observed, being more pronounced in less developed seedlings. It is concluded that glyphosate negatively impacts the early development of cowpea, particularly emergence and shoot growth. Earlier applications increase the crop’s susceptibility to the herbicide. The phytotoxicity scale was effective in quantifying damage. These results emphasize the need for further studies on glyphosate selectivity for this crop to optimize herbicide management in agricultural production.