Cotton needs to be maintained weed-free for at least the first 60 days. Cotton is a weak competitor with weeds during seedling stages and during early reproductive growth. While late-season weeds are unsightly and contribute to the weed seed bank for subsequent years, they are not as competitive.
Providing a weed-free seedbed allows cotton to be free from stress related to competition with weeds. When free of weeds, cotton receives more sunlight, has a better soil-water relationship, has better air movement to reduce disease pressure, and reduces host plants for insects.