Biochemical Composition of Forage Sorghum (Sorghum bicolor L) Varieties under Influenced of Salinity and Irrigation Frequency

Water stress is associated with low availability of water or with osmotic effects arising from salinity. Besides affecting crop yields, salinity may also influence biochemical composition and nutrient concentration of forage crops. For some impoverished regions of the world, sorghum remains a principal source of energy, protein, vitamins and minerals. To determine the effect of salinity on biochemical composition and nutrient concentration of forage sorghum [Sorghum bicolor (L.) Moench], two varieties of sorghum, Speedfeed and KFS4 were grown under rain shelter at salinity levels of 0, 5, 10, 15 dS m-1 and irrigated when the leaf water potential reached -1 (control), -1.5 and -2 MPa. The factorial treatment combinations were arranged in a randomized complete block design with three replications. Salinity and infrequent irrigation were found to significantly (P?0.01) affected the carbohydrate and proline levels in the forage sorghum varieties tested. High salinity of -15 dS m-1 and low water availability (-2 MPa) were increased the value of total soluble sugars by 48 and 19.3%, and the amount of free proline also by 60 and 15.1% respectively. When salinity and water stress increased, the concentration of monosaccharide fructose and glucose as well as sucrose as a disaccharide increased. With increasing levels of salinity to 5, 10 and 15 dS m-1, total sugar content increased 23.1, 35.9 and 48% respectively. Water stress with -1.5 and -2 MPa caused 6.9 and 19.3% increasing the amount of total sugar respectively. The study identified that both sorghum varieties were dissimilar to salt and water deficit, and accumulation of sugars and proline under stresses in shoot of KFS4 was greater than Speedfeed variety.