The aim of this research was to evaluate the effect of purple nutsedge (Cyperus rotundus) tuber density on the initial growth of cotton (Gossypium hirsutum) plants, cultivar Delta Opal. Boxes (0.60 x 0.60 x 0.25 m) containing red Latosol were used as recipients, where six cotton seeds were seeded in the center of the boxes spaced by 0.10 m; followed by the purple nutsedge tuber density in the boxes (0, 5, 10, 15, 25, 50, 75, 100, 125, 150, 175, 200 tubers per box), planted randomly. The experiment was arranged in a randomized complete block design with four replications. Height and the total chlorophyll content were determined 50 days after cotton seeding. At the end of the experiment (65 days after cotton emergence), height, total relative chlorophyll content, leaf area and dry weight of shoots and leaves were determined. The final number of shoots per box was evaluated in the purple nutsedge plants. The interference of the purple nutsedge in the initial growth of cotton initiated with 5 tubers/box, reducing up to 71% of the characteristics analyzed under the highest density (200 tubers/box). The intra specific competition was more intense in 75 tubers/box, when over 1.86 sprouts per tuber were obtained. The cotton characteristics most sensitive to the interference of purple nutsedge were: leaf area, leaf dry matter and plant stem and height.
weed; interference; development; leaf area
