Hormetics effects of glyphosate on coffee plants – guidelines for coffee

Abstract

Glyphosate stands out among non-selective herbicides used for management of weeds in coffee crops due to its favorable physical-chemical, economical, and environmental characteristics. The hormetic effect is the tonic effect of low doses of toxic substances, such as herbicides, on plants. The present study was conducted at the IFSULDEMINAS, Muzambinho campus, Minas Gerais, Brazil, to identify the hormetic effect of glyphosate on coffee seedlings (Coffea arabica cv. Catuaí Vermelho 144), using different low doses of the herbicide. The experiment was conducted in a randomized block design. The treatments consisted of 8 glyphosate herbicide low doses (0, 22.5, 45, 90, 180, 360, 720, and 1,440 g ha-1) distributed in three blocks, containing ten plants per plot, using a two-plant border between treatments, totaling 240 plants. The plant development over time was simulated using non-linear models. Growth models were adjusted using the Lorentz model to analyze the regression with four parameters. Stem diameter, plant height, and total leaf areawere evaluated from 7 to 63 days after the herbicide application. Hormetic effect on the coffee seedlings evaluated was found when using the low doses of 22.5 g ha-1 and 45 g ha-1, and the best effect was found with the low dose of 22.5 g ha-1. Low doses of 300 g ha-1 glyphosate stimulated the sprouting of coffee plants, and this dose is interesting for clonal seedlings. Key words: Chemical control; Coffea spp.; herbicide; phytotoxicity; low doses.