Investigation of Light Extinction Coefficient and Canopy Structure of More and Less Competitiveness of Rice Cultivars (Oryza sativa) Against Barnyardgrass (Echinochloa crus-galli)

The aim of this research was to compare more and less competitiveness of rice cultivars against barnyardgrass for light extinction coefficient and canopy structur. A filed experiment was conducted in 2007 growing season in Tonekabon’s rice research station in Mazandaran province. The experiment layout was a factorial design with four randomized complete blocks. Seven rice cultivars (Khazar, Sepidrood, Nemat, Dorfak, Fajr, Shiroodi, and Dailamani) and three lines (Line 830, Line 841 and Line 843) were transplanted with and without competition with barnyardgrass. Each cultivar or line was planted at its own optimum density, while density of barnyardgrass was 20 plants per square meter. Results showed that Khazar cultivar compare to Line 843, had higher light extinction coefficient. Under both weedy and weed free conditions, in Line 843, dry matter accumulation and leaf area in each layers of canopy were more than those for Khazar variety. Furthermore, in Line 843, dry matter accumulation and leaf area in top layer of canopy were more under weedy condition. On the other hand, the dry matter accumulation and leaf area of barnyardgrass in interference with Line 843 was less than that in interference with khazar cultivar.