Effect of plant density and nitrogen fertilizer different rates on sorghum cultivars forage yield

In order to study the effect of plant density and nitrogen fertilizer different rates on sorghum forage yield, an experiment was conducted in Agricultural Research Farm of Bojnourd region, Iran on Summer 2010. Experiment was carried out in split plot factorial based on Randomized Complete Blocks Design with 4 replications. Sorghum cultivars included speed feed and MFS1 cultivars in main plots and sub plots were combination of plant density 25, 30 and 35 plant/m2 and nitrogen application rate of Urea source included three levels 0, 100 and 200 kg N /ha. The result of analysis of variance showed that an increase in plant density on the surface unit leads to the reduction tillers. But it could increase plant height and LAI. The highest fresh and dry forage yield obtained in 350000 plants per hectare. Also results showed that nitrogen rate affected all the quantity traits si gnificantly except tiller number per plant, and plant height, in such a manner increased N use from 0 to 200 Kg N /ha increased 9, 12.96 percent in speed feed cultivar and in MFS1 line 10.91, 15.07 of fresh and dry forage yield respectively. The maximum fresh and dry forage yield obtained in speed feed cultivar. Finally it could be stated, maximum fresh forage (82.93 ton/ha) and dry matter yield (14.38 ton/ha) were obtained using 200 Kg N/ha and in density of 350000 plant/ha for speed feed early maturing cultivar.