Crop residues on the surface of the soil can interfere in the infestation of weed of summer crops. The objective of this work was to evaluate the effect of the amount of Gigantic guinea sorghum straw on the population of weed established in a no-tillage area. The experimental design used was the randomized blocks, with four replications. The treatments consisted of zero, 6,100, 7,100, 19,500, 26,700, 28,100 and 30,200 kg ha-1of guinea sorghum straw. Soybean (cv. Monsoy-6101) was seeded over the treatments in a density of 25 seeds m-1 and 0.45 m between lines. Thirty days after the sowing of the culture, weedevaluation was accomplished. It consisted of four samplings per plot, through metallic frames of 1 m². Significant reduction of the number of weeds was verified with the increment of the straw. The control of weeds is superior to ninety percent, from 15,000 kg ha-1 on.
Sorghum bicolor; cover crops; no-till
