Influence of tillage and crop residue on postdispersal predation of weed seeds

Field experiments were conducted from 1995 to 1997 in southern Ontario to d etermine the influence of tillage and ground cover on the quantity of postd ispersal seed predation of common lambsquarters and barnyardgrass, Ground-d welling invertebrates were the dominant seed predators and were responsible for 80 to 90% of all seeds consumed. Predation was highest in no-till and moldboard-plowed environments (averaging 32% in both) and lowest in chisel- plowed environments (averaging 24%). This indicates chat the relationship b etween the level of disturbance and predation is nonlinear and chat other f actors, such as the mobility of invertebrates and food availability may als o play important roles in determining the quantity of seed predation. In no -till, the type of crop residue also influenced the quantity of predation, with highest seed predation found in plots with corn residue (averaging 31% ) and lowest in those with soybean and wheat residue (24 and 21%, respectiv ely). It is apparent that there is an optimum combination of residue quanti ty and quality that maximizes the quantity of seed predation. Based on the experimental design used in this study, no feeding preference by seed preda tors was detected between common lambsquarters and barnyardgrass. Density-d ependent feeding, however, was evident for both species. Most biological co ntrol efforts have centered around predators with specific feeding habits. We contend that invertebrates with opportunistic feeding strategies that Fe ed on weed seeds may be the most significant broad spectrum and natural For m of biological weed control affecting weed population dynamics. Population s of beneficial arthropods should be conserved, and management strategies t hat augment the size of their natural populations should be encouraged.