POPULATION-DYNAMICS AND CONTROL OF ANNUAL WEEDS IN CORN (ZEA-MAYS) AS INFLUENCED BY TILLAGE SYSTEMS

Field research was conducted at Hancock, WI, from 1985 through 1987 to evaluate effects of conventional tillage, chisel plow, ridge tillage, and no-tillage systems on population dynamics and control of annual weed species in corn grown continuously on a loamy sand soil without irrigation. In all years of the study, green foxtail densities were greater in chisel plow and no-tillage than in the conventional tillage system, while ridge tillage had densities lower than all other tillage systems. Common lambsquarters density in the chisel plow system reached nearly 500 plants m-2 compared to less than 75 plants m-2 in the other tillage systems when averaged over years. Average redroot pigweed densities in the no-tillage and chisel plow systems were 307 and 245 plants m-2 compared to less than 25 plants m-2 in the conventional and ridge tillage systems. Horseweed was observed only in no-tillage and ridge tillage plots. Green foxtail and redroot pigweed were more difficult to control in chisel plow and no-tillage than in the conventional and ridge tillage systems with several herbicide treatments. Corn yields were not affected by tillage systems under weed-free conditions. Corn yield differences among tillage systems when the same herbicide treatment was applied appeared to be due to differences in weed control.