Black oat provides an excellent soil cover, and is a preferential winter crop mainly before soybean cultivation in Rio Grande do Sul, Brazil. The objective of this study was to evaluate the effects of black oat straw management on soil cover, soybean emergency, soil temperature and soil water content. The experiment was carried out during 1997/98, at the Federal University of Santa Maria, Santa Maria (RS), on a Typic Hapludalf soil. A completely randomized block design was used in a split-plot distribution with five replications. The main treatments with mechanical management of black oat straw were: (a) combined harvested straw; (b) not managed, stand-up straw; (c) straw rolled with a knife-roll; (d) disked straw; (e) mowed straw and (f) without straw cover and weed control. In the subplots, herbicide was applied with or without weed control at post emergency. The variables analyzed in the subplots with weed control were soybean emergency rate index, soil cover by straw, soil temperature and soil water content. It was observed that the stand-up and disked straw treatments reduced soil cover, respectively, by 20 and 74%, during the 53 days of evaluation; the maximum soil temperature was highest for the treatment without straw and weed control and lowest for the stand-up straw; excessive rainfall during the period of this study did not allow for differences in soil water content among the black oat straw management treatments. The soybean emergency rate index was not affected by the different types of black oat straw management, but was lowest in the treatment without straw.
black oat straw; mechanical management; soybean