EFFECTS OF PHYSICAL METHODS OF WEED-CONTR OL ON SUNFLOWER AGRONOMIC CHARACTERISTICS

During the 1990/91 season a field experiment was carried out at Estaca o Experimental Agromomica of Universidade Federal do Rio Grande do Sul , in Eldorado do Sul, RS, Brazil, in order to investigate effects of p hysical methods, others than weed control, on suflower agronomic chara cteristics. To compare treatments a split-plot design, was used where the main plots received or not nitrogen side-dressing (80 kg/ha of N), and on the subplots methods of weed control were applied. These treat ments consisted of various modalities: early hoeings performed by hand (with or without hill cultivation) or mechanically; early postemergen ce chemical control followed by late hand hoeing, or weed pulling, or oat residue mulching; and a weedy check. Sunflower traits were little affected by phsical methods and additional effects of hoeing were limi ted. No difference was found between hoeing performed manually or mech anically, and neither between early and late operations. The practice of hill cultivation did not affect characteristics investigated. Oat r esidue mulch presented negative effects, decreasing sunflower yield.