Seedling Parameters as affected by Soaking in Humic Acid, Salinity Stress and Grain Sorghum Genotypes

To study the effect soaking in humic acid and salinity stress on sorghum seedling parameters, a laboratory experiment accompanied in Seed Science Laboratory Faculty of Agriculture Mansoura University from June 2017 to July 2017. This exploration intended to study performance of seedling parameters of five grain sorghum cultivars viz. Dorado, hybrid 306, Giza 15, Mecca hybrid and H-305 to soaking in humic acid under salinity concentrations of 3, 6, 9, 12 and 15 dS/m-1beside the control, and humic acid soaking. The results showed that seed soaking in humic acid recorded the tallest shoot and root, weight of fresh shoot and root, weight of dry shoot and the lowest percentages of relative dry weight and highest salinity tolerance index. Seed soaking in humic acid exceeded shoot and root length (cm), weight of fresh shoot and root, weight of dry shoot and tolerance index by 14.3, 92.6, 8.7, 4.5, 4.7 and 40.8%, respectively compared without soakingin humic acid.The tallest shoot and the fresh shoot weight were produced from germinating Giza 15 cultivar. In addition, the tallest roots and highest values of stress tolerance index were recorded from sown Mecca hybrid and Giza 15 cultivars without significant differences. It could be stated that sown Mecca hybrid surpassed H-305 cultivar in root length by 36.3 %. Moreover, Giza 15 cultivar surpassed H-305 in shoot length, shoot fresh weight and stress tolerance index by 30.6, 10.1 and 29.1 %, respectively. The results clearly revealed that accumulative salinity concentrations from 3, 6, 9, 12 and 15 dSm-1 significantly produced the shortest shoot, root, weight of fresh shoot, root, weight of dry shoot, and root, highest percentages of seedling height reduction, and stress tolerance index, except the percentage of relative dry weight increased with salinity levels increased. The shortest shoot and root (cm), were recorded from the highest salinity concentrations of 15 dSm-1. The gradually increases in salinity till of 15 dSm-1 significantly diminished the length of shoot and root, the fresh weight of shoot and root, the dry weight of shoot and root, seedling height reduction percentages, and stress tolerance index by 51.7, 17.7,4.7, 59.5, 38.7 and 57.4, respectively compared the control treatment. Accordingly, sown Mecca hybrid or Giza 15 cultivar with soaking in humic acid under salinity of 6 dSm-1maximized seedling parameters and could recommended to cultivated in saline new reclaimed soils.