Physiological Changes and Yield in Speedfeed Sorghum and Millet Cultivares Affected by Delayed Irrigation

To evaluate drought tolerance of three cultivares of forage millet and one variety of sorghum, this experiment was conducted as split split plot based on a randomized complete block design with three replications. Irrigation frequencies consisted of irrigation after 80 (control), 120 and 160 mm evaporation from class A pan as main plots and sub-plots was consisted of sorghum cultivar (Sorghum bicolor cv. Speedfeed) and three cultivares of millet (Setaria italica cv. Bastan, Panicum miliaceum cv. Pishahang and Pennisetum americanum cv. Nutrifeed). Flage leaf sampling was done at three stages, before, one and three days after irrigation. According to the results, delaying in irrigation caused a reduction in leaf pigments and yield of forage, and it also increased proline, sucrose and soluble sugars of leaf.  Continuation of drought stress effects was observed in the days after irrigation. According to the results for the studied cultivars, 120 and 160 mm evaporations were the moderate and sever irrigation frequencies respectively. It needed at least three days to recover the effects of moderate stress. Speedfeed sorghum produced maximum yield, in each irrigation frequencies. The highest forage dry yield (9376 Kg/ha) belonged to speedfeed sorghum under normal irrigation for. There were positive correlations between yield and proline and sucrose as osmotic regulators, but leaf pigments had no significant correlation. Speedfeed sorghum had also high ability to adapt, and it repaired damages faster than millet cultivares after irrigation.