Black oat ( Avena strigosa [ Avena nuda]), an important winter cover crop in south Brazil, is a weed problem in cool season grain crops as well as ryegrass. Two trials in a randomized complete block design were conducted in Passo Fundo, Rio Grande do Sul, Brazil, to study different oat management methods applied on black oat at anthesis and milk stages to avoid it from becoming a weed plant in wheat cropped after soyabean. The plot area was 60 m 2. Nine treatments were tested in both trials: spray herbicide; roll plus herbicide; hay harvest; silage harvest; mowing; grinding, silage; rolling; disking; and grain harvesting. The average total biomass at anthesis was 5016 kg DM/ha and at milk stage was 6050 kg DM/ha. Soyabean cropped in the summer season yield 2080 kg/ha and it was not affected by black oat treatments. During the second year, the wheat plots sprayed herbicide before planting yielded 2472 kg/ha and spike density of 355/m 2, however, plots without herbicide yielded 836 kg/ha and had 225 spikes/m 2. On black oat milk stage managements, the yield average was 1733 kg/ha and 334 spikes/m 2, on sprayed herbicide plots before planting. In opposite, the plots without herbicide, wheat plants were completely dominated by resurgent black oat plants, due to managements applied during the previous winter. Mechanical management methods applied only in black oat development stages allowed seed germination during winter crops cycle. This problem is avoided by spraying herbicide before oat anthesis, because after that any management method tested was unsuccessful to control oat after the following winter crops, so it is necessary to spray herbicide before seeding winter cash crops.
