Bidens pilosa L. seeds were buried at 0 cm and 10 cm depths in the soil, with or without millet mulch, to test the effect of these variables on seed viability and dormancy during one year. The numbers of germinated and firm seeds were evaluated; the remained firm seeds in the soil were germinated in two environmental conditions, to estimate seed viability and dormancy, respectively. The germination and decay of seeds were more intense on the soil surface. Seed depletion was higher during the first rainy season and decreased during the dry season until the second rainy season. The mulch had no effect on seed depletion, probably due to its fast decomposition and no subsequent reposition. These results show that the concentration of B. pilosa seeds on the soil surface, by practices such as no-tillage, can increase seedling emergence on short-term, which demands weed control practices, but at long-term it increases the depletion rate of the seed bank in the soil.
weeds; direct sowing; germinability; seed dormancy; viability
