EMERGENCE OF WEED SPECIES ( Brachiaria ) UNDER SUGARCANE STRAW

ABSTRACT The objective of this study was to evaluate the effects of soil cover with sugarcane residue on weed emergence of four weeds from the genus Brachiaria. The study was conducted in an area whose soil was classified as Red Nitosol. Seven different amounts of sugarcane residue (0, 3, 6, 9, 12, 15 and 18 ton ha-1) were used as soil cover. The residue of variety SP832847 was used upon four weed species: Brachiaria decumbens, B. brizantha, B. ruziziensis, and, B. humidicola. The experimental design was a randomized block with four replications. The weeds were sown 1 cm deep and covered by the residue. The seeding rate in use was 1,200 plants m-2. The study was comprised of two phases: the first phase was an evaluation of plant emergence (more than 1 cm for shoots) at 9, 12, 19, 34 and 43 days after sowing (DAS), and in the second phase, plant emergence was evaluated after removal of the straw residue at 89, 130, 175, 196, 217 and 234 DAS. The amount of sugarcane residue used as soil cover influenced the emergence pattern of Brachiaria spp. Minor germination was noticed after residue removal. Amounts greater than 9 ton ha-1 decreased the total number of seedlings in all species, except for B. ruziziensis, whose emergence decreased at 12 ton ha-1.