EFFECT OF WEED COMPETITION ON THE GROWTH OF GLYPHOSATE-RESISTANT TRANSGENIC SOYBEAN

Abstract

In order to study the effect of weed interference on soybean under no-tillage system, an experiment was carried out in the northern region of Mato Grosso. The treatments consisted of controls (weeded and infested) and different periods of coexistence and weed control (presence or absence of weeds until 15, 30, 45 days after emergence). The soybean cultivar was M 9056RR, with a spacing of 0.50 m between rows and a population of 280,000 plants ha-1. The results reflected the competitive relationships between the soybean crop and the weed community, which was composed of six species, in which Sorghum halepense was the most important species due to its predominance in the experimental area. The interference imposed by weeds caused etiolation of soybean plants and reduced the number of pods per plant and grain yield, indicating that the crop, under the experimental conditions, suffered irreversible interference from the weed community. Under these conditions, the interference imposed by the weeds caused a change in the average height of the plants and the height of insertion of the first soybean pod and reduced the number of pods per plant, weight of 100 grains and grain yield, which was reduced around 62%.