Fields being prepared for the planting of annual row crops such as corn are also unfortunately being prepared for the germination and growth of many annual weeds. In fact, the number of weed seeds in an acre of cropland can range from a few million to over 100 million. If allowed to grow, the weeds will competeand all too wellwith corn for water, nutrients and light.
Some weeds can tolerate cold, wet conditions better than corn, thus get a head start on the crop.
This publication identifies and illustrates the principal annual broadleaf weeds of corn, discusses their likely effects on corn yield depending on when they become competitive, and presents recommended cul- tural and chemical methods for control. This is because it is a prolific seed producer, and those seeds remain viable in the soil for years. Redroot pigweed grows throughout the U.S. and reduces yields in all parts of the Corn Belt and the South. Like pigweed, velvetleaf seeds remain viable for many years, allowing new stands of the weed to germinate each season. However, since they are easily controlled by herbicides, populations of these two weeds have changed little over the years.