Effect of seed pre-soaking on compensation of late planting of two forage sorghum (Sorghum bicolor (L.) Moench) cultivars in second cropping

To evaluate the effect of seed pre-soaking on forage yield and quality and water productivity in late planting of two forage sorghum cultivars, a field experiment was conducted was conducted as split factorial arrangements in randomized complete block design with three replications in 2017 and 2018 growing seasons at the research field of Seed and Plant Improvement Institute, Karaj, Iran. Four planting dates; July 1st, July 10th, July 23rd, and August 1st were assigned to the main plots, and factorial arrangement of seed treatments (without pre-soaking as control and seed pre-soaking) and sorghum cultivars (Peghah and Speedfeed) were randomized in sub-plots. The results showed that days from planting to the emergence of sorghum cultivars were reduced by four to six days, at different sowing dates, as affected by seed pre-soaking treatment. Late planting significantly reduced forage production, dry matter yield, protein yield, and digestible dry matter yield but improved crude protein content and dry matter digestibility. The highest fresh and dry forage yields (147.79 and 32.82 ton ha-1, respectively) and the maximum digestible dry matter and protein yield (18498 and 2904 kg.ha-1, respectively) were obtained in seed pre-soaking treatment of cv. Speedfeed in July 1st planting date. The highest water productivity for dry matter production (7.22 kg.m-3) was recorded in seed pre-soaking treatment of cv. Speedfeed in July 23rd planting date. Although seed pre-soaking reduced the digestibility of dry matter by 0.64% compared to without pre-soaking treatment, but significantly increased digestible dry matter yield and protein content. Peghah cultivar was superior for crude protein content and dry matter digestibility, and cv. Speedfeed for forage yield and water productivity. Based on the results of this experiment, seed pre-soaking treatment could compensate for the delay planting of two forage sorghum cultivars by increasing forage yield. The results of this experiment also showed that seed pre-soaking and July 1st planting date were more effective on the performance of cv. Speedfeed.