Effects of physical methods of weed control on sunflower agronomic characteristics

Abstract

During the 1990/91 season a field experiment was carried out at Estação Experimental Agronômica of Universidade Federal do Rio Grande do Sul, in Eldorado do Sul, RS, Brazil, in order to investigate effects of physical methods, others than weed control, on sunflower agronomic characteristics. 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 treatments consisted of various modalities: early hoeings performed by hand (with or without hill cultivation) or mechanically; early post-emergence chemical control followed by late hand hoeing, or weed pulling, or oat residue mulching; and a weedy check. Sunflower traits were little affected by phisical methods and additional effects of hoeing were limited. No difference was found between hoeing performed manually or mechanically, and neither between early and late operations. The practice of hill cultivation did not affect characteristics investigated. Oat residue mulch presented negative effects, decreasing sunflower yield.