The objective of this study was to evaluate rates of glyphosate herbicide applyed alone or in mixture with 2,4-D ester herbicide, to control nativo pasture before planting soybeans in a no-till system. The following treatments were tested: glyphosate at 360, 720, and 1080g ha-1 of acid equivalent, alone or in mixture with 200g ha-1 of 2,4-D, sprayed at two volumes (50 and 200l ha-1), and unsprayed control. Herbicides were sprayed in 10/30/95 and soybean was seeded in 12/27/95 in study carried out at the Federal University of Santa Maria campus. Santa Maria, RS, Brazil. The main plant species out of the 57 identified were Paspalum notatum var. notatum biotypes "C" and "D", Vernonia nudiflora, Vernonia polyanthes, Eryngium horridum e Baccharis trimera. The reduction in the spray volume from 200 to 50l ha-1 and mixing with 2,4-D did not affect the efficacy of glyphosate, which showed general control of 48, 73, and 90% using 360, 720. and 1080g ha-1. respectively. Glyphosate did not control V. nudiflora, V. polyanthes and E. horridum, but controlled B. trimera at rates of 720 and 1080g ha-1. There were 54, 79, and 93% control of Paspalum spp. using 360, 720, and l080g ha-1 of glyphosate, respectively. Soybeans yields were 1762, 2502, 2690, and 2793 kg ha-1 for unsprayed and 360, 720, and 1080g ha-1 of glyphosate, respectively. It is concluded that for soybean seeding over native pasture, the rate of 1080g ha-1 of glyphosate is adequate.
glyphosate; 2,4-D; diluent volume
