Yield evaluation of promising lines of dual-purpose grain-forage sorghum [Sorghum bicolor (L.) Moench] at different harvesting times

To evaluate the grain and forage yield in promising sorghum lines, a two years factorial experiment in a randomized complete block design with three replications was conducted in Seed and Plant Improvement Institute, Karaj, Iran, during 2017 and 2018 cropping seasons. Experimental factors included harvesting time at four levels (milk, soft dough, hard dough and physiological maturity stages of grain) and dual-purpose grain-forage sorghum genotypes at seven levels (KDFGS4, KDFGS6, KDFGS9, KGFGS10, KDFGS16, MDFGS1, and MDFGS2). Maximum and minimum grain yields (6847 and 4061 kg.ha-1, respectively) were obtained from KDFGS6 and KDFGS16 lines, respectively, whereas the maximum and minimum 1000-grain weight (35.27 and 22.03 g, respectively) were recorded in KDFGS6 and MDFGS2 lines, respectively. MDFGS1 line produced the highest silage forage (101.73 ton.ha-1) at the grain soft dough stage, and the highest dry matter (38.13 ton.ha-1) at the grain physiological maturity stage. In total, according to the results of this experiment, KDFGS6 line is introduced as the best dual-purpose genotype for grain-forage production and MDFGS1 line as the suitable genotype for forage production. Furthermore, based on the suitable dry matter percentage of forage for silage production, it is recommended that the forage of promising dual-purpose sorghum lines be harvested at the grain soft dough stage. Therefore, forage harvesting from MDFGS1 promising line at the end of the soft dough stage is suggested as the superior treatment of this experiment for silage production.