The weed seedbank was estimated at the conclusion of
the 4-year experiment as a measure of the cumulative
treatment effects on weed growth and competitive
ability with winter wheat. Nitrogen application timing-tillage intensity affected the seedbank of two of three
weed species (Table 6). The seedbank of B. tectorumwas
lowest with the fall-tilled treatment. Tillage is known to
stimulate germination of some weed species (Anderson,
1998) and this may have contributed to greater B.
tectorum seed loss over time in our experiment. In
contrast, the seedbank of D. sophiawas greatest for fall-tilled. This weed has a high level of seed dormancy (Best,
1977), thus the germination promotion effects of tillage