بررسی اثر فاصله ردیف، آرایش کاشت و زمان مصرف کود نیتروژن بر کنترل علف‌های‌هرز مزارع سورگوم علوفه‌ای

In order to investigate effect of row spacing, planting pattern and time of nitrogen fertilizer application on sorghum in weed control in forage sorghum, a field experiment was conducted in two region ( Tehran and Shahrood). The experiment design was split-split plot in randomized complete block design with three replications. In the main plots, row spacing was at three levels including 55, 65 and 75 cm, planting pattern at two levels including one and two rows per ridge as in sub-plot. The time of nitrogen application was in sub-sub-plots at four levels including a) 25% before planting, 25% in the seven-leaf stage of sorghum, 25% after the first cutting, 25% in the five-leaf stage of re-growth sorghum b) 15% before planting, 35% in the seven-leaf stage of sorghum, 25% after the first cutting, 25% in the five-leaf stage of re-growth sorghum c) 25% in the three-leaf stage of sorghum, 25% in seven-leaf stage of sorghum, 25% after the first cutting, 25% in the five-leaf stage of re-growth of sorghum and d) 15% in the three-leaf stage of sorghum, 35% in seven-leaf stage of sorghum, 25% after the first cutting, 25% in the five-leaf stage of re-growth of sorghum. Sampling of weeds was performed before first harvest and 15 days after that. Results indicated that only change of planting pattern from one row to two rows per ridge significantly reduced weed density and biomass. This results on increasing forage yield in first cutting. Planting pattern had no effect on sorghum forage quality. The time of nitrogen application and row spacing treatments and their interactions had no significant effect on weed control, forage quality and quality.