Competition effect of cotton on growth, leaf area and its vertical distribution in canopy of velvetleaf

To evaluate the competition effect of cotton planted in different row spacings on growth, leaf area and its vertical distribution in canopy of velvetleaf an experiment was conducted in a completely randomized block design with split plot arrangement of treatments with three replications at Experimental Station of Gorgan University of Agricultural Sciences and Natural Resources during 2011 growing season. Result showed that maximum velvetleaf leaf area index with 6.1197, was obtained in plot of 12 plant /m-2 density and 80 cm cotton row spacing. 50% of maximum velvetleaf leaf area index was achieved after 1229, 1067.1 and 1219.8 growth degree day in 20, 40 and 80 cm of cotton row spacing, respectively. According to result of vertical distribution of leaf area study, maximum cotton leaf area in UNR, was observed in 5 plant.m-2 weed density and the most of this leaf area, with 27586.4 cm-2, was distributed at 75 cm cotton height. Maximum velvetleaf leaf area was observed in cotton planted in ultra narrow row (UNR) and 12 plant /m-2 weed density; the maximum amount of leaf area in this condition with 20870.34 cm-2 was distributed in 175 cm velvetleaf height. In contrast, in conventional row (CR) system the maximum velvetleaf leaf area was observed in 12 weed plant /m-2, and the maximum leaf area in this condition, with 34351.18 cm-2, was distributed at 225 cm velvetleaf height. In CR system, maximum cotton leaf area was obtained in no weed plant /m-2 and maximum produced leaf area in this condition, with 21658.5 cm-2, was distributed at 100 cm plant height.