Abstract

The objective of this study was to evaluate the residual effect of glyphosate and 2.4-D herbicides in the initial development of the soy crop in a Yellow Red Latosol. The experiment was conducted in randomized design, consisting of 4 different doses of herbicides (0, 1, 2 and 5 times the recommended dose of the glyphosate and 2.4-D mixture), applied at intervals of 0, 3, 7 and 10 days before sowing, with 4 repetitions on a soybean culture (Monsoy 8372rr cultivar) performed up to 28 days after sowing, at 7 days intervals. The variables analyzed were plant height, leaf area, phytotoxicity, aerial dry biomass, root dry biomass and chlorophylls a and b, the latter being performed from the second evaluation after sowing. For the conditions evaluated, plant height, leaf area and aerial dry biomass were lower in the plants that received the highest doses of the glyphosate mixture and 2.4-D. The higher doses of glyphosate and 2.4-D resulted in higher symptoms of phytotoxicity in transgenic soy plants. The periods of application of the glyphosate herbicide mixture plus 2.4-D closer to the date of sowing of the soybean were the ones that most harmed the development of the crop.

Key words: Transgenic soy, phytotoxicity, initial development.

Abbreviation

UFMT, Federal University of Mato Grosso; RYLd, Red Dystrophic Yellow Latosol;  RPTN, Relative Power of Total Neutralization; NPK, Nitrogen, Phosphorus, Potassium; CRD, Completely Randomized Design; RDM, Recommended Doses of the Herbicide Mixture; DAS, Days after Sowing; DBS, Days before Sowing;