Wild oat (Avena fatua L.) is a major weed in barley (Hordeum vulgare L.) in
Argentina. During 1993, 1994, 1995, and 1996, demographic studies of wild
oat in barley crops Here conducted to assess the effect of herbicide treatm
ent, crop, and sowing rate on the demographic processes of seedling establi
shment, survival rate, reproductive performance, preharvest seed dispersal
rate, and fate of seed in the soil during the fallow period. The herbicide
was diclofop-methyl: methyl 2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic aci
d. Increasing barley sowing rate from 160 plants m(-2) to 280 plants m(-2)
effectively reduced the amount of wild oat seeds that entered the soil seed
bank by 50% through lowering fecundity. Diclofop-methyl reduced the number
of seeds that entered the soil seed bank sevenfold (1050 us. 140 seeds m(-
2)) through a reduction in both seedling survivor rate and reproductive out
put. In addition, the diclofop-methyl treatment delayed the onset of seed m
aturity and reduced the dormancy level of the seeds produced by the survivi
ng plants. Half the number of wild oat seeds entered the seed bank in a bar
ley than in a wheat (Triticum aestivum L.) crop. This was through a lower w
ild oat reproductive output and a higher rate of seed dispersal related to
the later harvest time of wheat relative to barley. These data indicate tha
t integrated control of wild oat should include herbicide treatment, crop s
election, and sowing rate.