The aim of the study was to determine the influence of different
methods on breaking seed dormancy of weed species velvetleaf (Abutilon
theophrasti Medik.) and redroot pigweed (Amaranthus retroflexus L.).
The influence of seed sowing depth on emergence and growth of weeds
was also evaluated. The results showed that the best treatment for breaking
seed dormancy of velvetleaf was immersion of seeds in hot water (60°C)
for 1 hour, while immersion in distilled water and 0.2% KNO3 solution
had no significant effect. Seed germination of redroot pigweed was significantly
increased in all treatments, however 2% KNO3 solution and cold
stratification at 5ºC for 12 days had the greatest effect. Treatments had
different influence on mean germination time, seed germination dynamics
and seedling length of weeds. The highest percentage of emerged velvetleaf
seedlings was recorded when seeds were sown at 1 to 4 cm depths
and ranged from 55.6 to 67.9%. With the increase of sowing depth the
emergence percentage decreased, however one quarter and one fifth of the
seedlings emerged from 7 and 9 cm depths. Both seedling length and fresh
weight were greater at lower sowing depths. Emergence of redroot pigweed
was not significantly influenced by sowing depth, however seedlings
length and fresh weight were greater at 5 cm depth than at 1 cm.