Interference between jimsonweed and soybean was investigated. Jimsonweed growing within the soybean row had little influence on vegetative characteristics of soybean during the first 12 wk of the growing season. The influence of an individual jimsonweed plant was first detected 10 wk after planting and extended 20 cm within the row. At harvest, interference extended 50 cm from individual jimsonweed plants, and yield within the 1.2 m of row surrounding a single jimsonweed plant was reduced 12%. Jimsonweed spaced 60 cm apart within the row reduced yield 18%. Soybean interference with jimsonweed growth increased steadily during the season, reducing the size of jimsonweed plants within the soybean row 80 to 93% compared with jimsonweed plants free of soybean interference. Jimsonweed grown within the soybean rows produced an average of 4900 seeds per plant whereas jimsonweed grown crop-free produced nearly 69 000 seeds per plant.
