Effect of rippled canopy on light competition between Soybean and Redroot pigweed (Amaranthus retroflexus) in Sole and Intercropping

Field experiment was conducted to evaluate effect of canopy structure on growth analysis, light absorption and weed competition of two soybean cultivars in sole and mix cropping. A factorial design based on randomized complete block with three replications was carried out in field research station, University of Tehran, Karaj. Two soybean cultivars including Clark (tall) and Interprice (dwarf) were planted in sole and intercropping in competition with redroot pigweed at densities of 0, 2, 4 and 8 plant/m-2. Light absorption and canopy structure assessed in canopy closure. The results realized that, in mixed cropping Redroot pigweed had less CGR (4 g/m2d) and less cumulative biomass (234 g/m2) compare to sole cropping. Canopy surface in intercropping increased 20% compared to the sole cropping and the light extinction is occurred in 60 cm of soybean high. Light absorption in the development time of canopy for Clark and Interprice were 84% and 64% respectively. This tow cultivars supplementary complete each other for light absorption because of the height difference between them and inter specific competition dominated by intra specific competition.