Recovery of common agricultural weeds after burial by soil was studied in
four greenhouse and three field experiments. Species studied included
velvetleaf, Powell amaranth, common lambsquarters, barnyardgrass, and giant
foxtail. Seedlings were bent over before burial to simulate the effect of
the impact of soil thrown by a cultivator. Altogether, more than 35,000
seedlings were marked and observed for recovery. No seedlings recovered from
4 cm of burial. Recovery from complete burial under 2 cm of soil ranged from
0 to 24% depending on the experiment, species, and watering treatment, but
recovery greater than 5% was rare. Large-seeded species tended to recover
from complete burial under 2 cm of soil better than small-seeded species.
The study did not reveal a difference in recovery of grasses relative to
broadleaf weeds. Overall, seedlings tended to recover best when water was
applied daily after burial, worst when water was applied once on the day of
burial, and to an intermediate extent when no water was applied. However,
difference in recovery between the no-water and watering-once treatments
were usually small. Also, many experiment by species combinations showed no
significant differences among watering treatments. When even a small portion
of the seedling was left exposed, recovery generally exceeded 50%. Organic
weed management systems commonly use burial of weed seedlings with tine
weeders and soil thrown by sweeps and hilling disks to control weeds in crop
rows. Recovery from burial could pose a substantial weed management problem
in some circumstances, particularly for large-seeded weed species.
Maximizing burial depth is important for limiting recovery. Recovery from
burial can be minimized by withholding irrigation for several days after
hilling-up operations.