Effect of sowing time on growth and yield of forage sorghum (Sorghum bicolor L.) cultivars in second cropping in temperate region of Lorestan province

To determine the best sowing time and cultivar of forage sorghum in summer cropping as a substitute for maize under water deficit conditions in the temperate region of Koohdasht, Lorestan, Iran, a split plot
experiment in randomized complete block design layout was conducted with four replications and four planting times (June 25 and 2th, 9th and 16th July) (after wheat harvest) and two forage sorghum cultivars (Pegah and Speedfeed) in main and sub plots, respectively, in the summer of 2013 and 2014 at Lorestan Agricultural and Natural Resources Research and Education Center, Khorramabad, Iran. Results showed that delayed planting reduced dry matter accumulation and crop growth rate (CGR) and Pegah cultivar performed better than Speedfeed cultivar. Maximum plant height was achieved in Speedfeed cultivar in second planting time in first and second years (173.3 and 211.6 cm, respectively). Pegah cultivar had better performance than Speedfeed in leaf area index and stem diameter in most planting times. Pegah cultivar in first planting time had highest fresh forage yield (94.0 and 110.2 ton.ha-1 in first and second years, respectively) and delay planting reduced dry and fresh forage yield. It concluded that the maximum dry and fresh forage yield of sorghum
(cv. Pegah) could be produced in June seed sowing and seems to be more suitable for temperate regions like Koohdasht, Lorestan, Iran.