All yield data were further analyzed separately for each year as there was an interaction between years and treatment levels for the beginning and the end of the CPWC. The duration of weed-infested or weed-free period fluenced the relative yield of corn, regardless periods of weed . Yield from the season-long weed-free plots ranged from 7.8 to 9.3 ha-1 in field corn, 2.7-3.9 t ha-1 in popcorn, and 7.6-10.2 t ha-1 in sweet corn with much lowel yield of 2.2-4.6 t ha-1 in fieldcorn,0.59-2.0 t ha-1 in popcorn, and 3.6-5.5 t ha-1 in sweet corn in the season-long weedy plots.