It is known that cover crops can influence on seed quality, as well as on yield cropping. This trial analyzed possible allelopathic interferences of black oat (Avena strigosa Schreb.) remains and a consortium of black oat, forage turnip (Raphanus sativus L.) and vetch (Vicia sativa L.) on cropped seeds quality and soybean yield according to different intervals between the drying of some cover crops with Glyphosate 480 (3 L had) herbicide and seeding with BRS 232 cultivar. Plots of 5.0 m x 2.5 m were established, plus 1 m of edge between each of them. The cover crop was sown in August, 2006, with 0.15 m of width among rows: the parcels were dried in intervals of one, ten, twenty and thirty days before the soybean seedling. Four treatments were arranged for black oat cover, four for consortium and one control for each cover, all randomized, with five replications. The soybean was seeded in November, 2006, with 0.45 m width among seeding rows. Data as yield, adjusted to 13% of moisture content on cropped seeds; seedling rate; weight of 100 seeds; moisture content and seeds vigor were recorded by the accelerated aging test. All the tests were submitted to an experimental design, with subdivided plots (split plot), completely randomized; the averages were also compared using Scott-Knott test at 5% of probability. The data showed a possible allelopathic interference of cover crops on soybean seed quality. The greatest weight of 100 seeds was obtained when soybean was sown under black oat cover compared to the consortium. On the other hand, when it was sown under consortium, it showed the best vigor, evaluated by the accelerated aging test. The yield did not differ between both covers. The intervals between drying and sowing interfered on weight of 100 seeds and soybean yield. The interval between drying and sowing of one day had a positive effect on weight of 100 seeds, but soybean yield decreased. Hence, it is not well recommended to sow soybean next to the drying management of a cover crop.
