EFFECT OF PLANTING DATE AND APPLICATION OF NITROGEN ON YIELD RELATED TRAITS OF FORAGE SORGHUM CULTIVARS

In order to study the effect of planting date and nitrogen nutrition on yield of two forage sorghum cultivars, a split factorial experiment with four replications was conducted on 2012 growing season in Fariman, Iran. Main factor belonged to planting dates, including June 10, June 26 and July 16. Combination of cultivars, Speedfeed and Jumbo, and nitrogen application, Control, 75 and 150 kg.ha-1 net nitrogen, were adjusted as sub plots. Results showed that with delaying of planting date, the total dry matter and fresh forage yield was decreased. The highest fresh and dry forage yield was achieved in June 10 treatment. Leaf area index, leaves number, tillering, and fresh forage yield were affected by nitrogen. Speedfeed was superior to Jumbo in its fresh and dry biomass, specially in the treatment of June 10, that this cultivar produced 87.2 ton.ha-1 fresh biomass.