RESIDUAL EFFECT OF AUXINIC HERBICIDES ON SOY

Abstract

The control of weeds in pastures is essential to improve the productivity indexes of agricultural activity and the correct and conscious use of herbicides is very important to reduce the problems caused by the residual effect in subsequent culture. Thus, this study evaluated the residual effect of the auxinic herbicides 2,4-D, picloram and 2,4-D + picloram on the initial development of soybean seedlings. The work was carried out in a greenhouse in a completely randomized design, in a 7 x 3 factorial scheme, with four replications. The first factor was composed of the percentages of the recommended doses of herbicides (100%, 50%, 25%, 12.50%, 6.25%, 3.12% and 0.00%) in which the highest dose (100% ) was equivalent to 2 L ha-1. The second factor was composed of the herbicides: 2,4-D, Picloram + 2,4-D and Picloram. The number of plants emerged for each treatment at 10 DAS, plant height and accumulation of fresh and dry mass at 40 DAS were evaluated. The herbicide picloram negatively affects the variables number and height of plants from the dose 3.12% and fresh and dry mass from the dose 6.25% and the herbicide picloram + 2,4-D negatively affects the variables number of plants from 3.12% dose, height plant from 6.25% dose and fresh and dry mass from 12.5% dose. Soy showed high sensitivity to picloram residues in the soil. The 25% and 50% doses, respectively, of the herbicides picloram + 2,4-D and picloram, limited the seedling emergence and the 100% dose prevented the germination of soybean seeds. No residual effect was observed for the herbicide 2,4-D in soybean seedlings in any of the studied doses.