Experiments were conducted in 1998 and 1999 at the Central Crops Research Station near Clayton, NC, to evaluate density-dependent effects of Datura stramonium on weed growth and seed rain and Gossypium hirsutum growth and yield. Datura stramonium height was not affected by density in either year. Crop height never exceeded weed height during the growing season, indicating that competition for light occurred between the two species. Eight weeks after planting or later, G. hirsutum height decreased as D. stramonium density increased. An increase in D. stramonium density from 1 to 32 plants (9.1 m of row)−1 resulted in a decrease in capsule production per plant of 92 and 60 in 1998 and 1999, respectively. Total D. stramonium dry weight per 9.1 m of row increased via a quadratic relationship as weed density increased. Gossypium hirsutum lint yields decreased as D. stramonium biomass and density increased in both years. Estimated yield losses of 10 and 25% were caused by D. stramonium at 0.5 and 1.5 plants (9.1 m of row)−1 (572 and 1,716 plants ha−1), respectively, in 1998 and 0.6 and 1.8 plants (9.1 m of row)−1 (690 and 2,060 plants ha−1), respectively, in 1999.
