Nutritional value and agronomic traits of forage sorghum under drought stress

Abstract

Drought negatively affects the crop yield and nutritional value of forage sorghum. The effect of drought on forage sorghum was investigated in a two-year, strip plot field experiment with a randomized complete block design. The vertical factor included four levels of drought stress (mild, moderate, severe, and extreme), and the horizontal factor consisted of four forage sorghum genotypes (Spidfid, Sugargraze, Jumbo, and Pegah). The results showed that drought stress negatively influenced plant height, number of leaves, biomass, leaf-to-stem ratio, and seed yield and yield components, as well as crude protein and prussic acid contents of sorghum. However, the different genotypes did not show the same responses to drought stress. The highest forage yield was observed in Spidfid genotype under mild stress by 121.6 ton/ha, the lowest related value (30.5) was obtained in Sugargraze genotype under extreme drought. The highest seed yields were recorded in the Spidfid genotype in mild and extreme stress treatments (7861 and 4839 kg/ha, respectively). The Sugargraze genotype showed the highest yield reduction under extreme stress. The nutritional value of forage was significantly higher in the Spidfid genotype, and the same genotype contained the lowest prussic acid content under mild and extreme stress conditions by 87 and 86 mg/kg, respectively. However, the crude protein content of the genotypes was not significantly different under severe stress. Therefore, using the Spidfid tolerant genotype and reducing the irrigation period in water shortage conditions, can be a promising solution to achieve the ideal quantitative and qualitative yield of sorghum forage.