Doses e épocas de aplicação de 2,4-D em trigo

Abstract

The identification of the application stage and the correct dose of 2,4-D herbicide is important so that wheat is not harmed. The objective of this study was to evaluate the effect of 2,4-D doses applied at different stages of wheat crop development. The experiment was conducted in a randomized block design, arranged in a 4 x 5 factorial scheme, with four replications. In factor A, the application stages (before tillering, tillering, first node and rubberiness) were allocated and the doses of 2,4-D (0, 349, 698, 1047 and 1396 g e.a ha-1) were allocated. The variables evaluated were: phytotoxicity at 7, 14, 21, 28 and 35 days after application of the treatments (DAT), photosynthetic activity, CO2 internal concentration, stomatal conductance, water efficiency and carboxylation. The number of spikes m-2, ear length (cm) and number of full and sterile grains were determined in the pre-harvest. The mass of one thousand grains (g), grain yield (kg ha-1) and hectoliter weight (kg hL-1) were determined after harvest. The results demonstrate that the herbicide caused phytotoxicity to wheat, being elevated with increasing doses and mainly before tillering, causing grain sterility, and decreased productivity. The other components of yield did not present difference when increasing the dose and application in different stages as well as the physiological variables. The increase of the 2,4-D doses applied before tillering and in the booting production decreased linearly the grain yield of the wheat.