THE EFFECT OF LIGHT DURING AND AFTER SOIL CULTIVATION WITH DIFFERENT TILLAGE IMPLEMENTS ON WEED SEEDLING EMERGENCE

The purpose of this study was to investigate the role of sunlight perc eived by weed seeds during and after soil cultivation with moldboard a nd chisel plows on induction of seed germination. Daytime cultivation with a moldboard plow increased weed seedling emergence by as much as 200% above the levels recorded following nighttime cultivation; howeve r, the magnitude of this promotion varied depending on season and fiel d history, and occasionally it was nil. In contrast, when a chisel plo w was used in primary tillage, no differences in seedling emergence we re observed between daytime and nighttime cultivation. The absolute ge rmination level in plots cultivated with a chisel plow was at least 20 0% greater than in plots cultivated with a moldboard plow. This observ ation suggests that microenvironmental factors other than light played an important role in promoting seed germination in chisel-plowed plot s. Covering moldboard-plowed plots with opaque plastic immediately aft er cultivation did not reduce weed seedling emergence compared to plot s that were either covered with transparent film or left uncovered. Ou r results suggest that only the light stimulus perceived by the seeds during soil cultivation is effective in triggering germination.