The effects of row spacing and plant density on light extinction coefficient (k) and grain yield of sunflower Al-star cultivar.

In order to determine the effects of row spacing and plant density on yield and yield components of sunflower, an experiment was conducted at Azad University Farm Station of Saveh in summer of 2005. The layout of experiment was split plot with complete randomized design with four replications. Three spacing: rows 30; 40 and 50 cm.as the main plots and five plants densities: 8, 10, 12, 14 and16 plants per square meter were studied, as subplots, respectively. The increasing of plant density caused a rise in extinction coefficiency, growth indices, such as CGR and LAI at the pollination time. The results of this experiment showed that, the greatest grain yield was about 4.5 T/ha and was obtained in the 50 cm. row spacing and 16 plants. /m2 density. The plant density had no significant effect on grain yield components. However, the increase of plant density caused a reduction in 100-seed weight. The increase in the number of capitulum's per square meter of field in higher plant densities, compensated the other grain yield components, and as a result the grain in higher plant densities were increased. The greatest yield of 4 t/ha was obtain where row spacing was 50 cm. and the lowest yield of 3.7 t/ha was produced where the raw spacing was 30 cm.