“…INTRODUCTION N UM EROUS investigations have provided abundant data on the competitive ability of weeds. Considerable weed competition research in crop species has dealt with weeds and their influence on cereal grains (2,8,11,14,16), flax (Linum usitatissimum L.) (1,3,16), and sorghum (Sorghum bicolor (L.) Moench) (20). The critical period of weed competition has been a common objective in many weed-crop competition studies (6,7,9,10,12,13,17).…”