Effects of Different Water Stress Levels on Biomass, Root Yield, and Some Physiological Parameters of Sorghum

This study was conducted under water stress conditions for two years (2017-2018) to investigate the effects of different water stress levels on biomass yield, root yield, root/shoot ratio, some physiological characteristics, Water Use Efficiency (WUE), seasonal water consumption, and yield reduction ratio of silage sorghum. Experiments were conducted in randomized blocks design. There were four different irrigation treatments including I 1 : Full irrigation; I 2 : 75% of I 1 ; I 3 : 50% of I 1 , and I 4 : 25% of I 1 ).). In 2017, dry biomass yields varied between 14.11 (I 4 ) and 26.02 t ha -1 (I 1 ), stomatal conductance between 72.2 (I 4 ) and 147.8 mmol m -2 s -1 (I 1 ), chlorophyll contents between 37 spad (I 4 ) and 42.1 spad (I 1 ), canopy temperatures between 27.2 (I 1 ) and 31.3 o C (I 4 ), and WUE between 4.5 (I 1 ) and 5.5 kg m -3 (I 3 ). In 2018, dry biomass yields varied between 14.51 (I 4 ) and 25.92 t ha -1 (I 1 ), stomatal conductance between 69.9 (I 4 ) and 129.5 mmol m -2 s -1 (I 1 ), chlorophyll contents between 39.7 spad (I 4 ) and 43.9 spad (I 1 ), canopy temperatures between 30.0 (I 1 ) and 34.5 o C (I 4 ), and WUE between 4.2 (I 1 ) and 4.9 kg m -3 (I 4 ). Based on two-year averages, dry root yields varied between 8.15 (I 4 ) and 13.27 t ha -1 (I 1 ), root/shoot ratios between 0.51(I 1 ) and 0.57 % (I 3 -I 4 ), seasonal water consumptions between 281(I 4 ) and 598 mm (I 1 ). Water stress reduced biomass yield, root yield, stomatal conductance, and chlorophyll contents, and increased WUE and root/shoot ratios. Biomass yields decreased with increase in water stress, but this decrease was lower compared to the decrease in applied irrigation water quantities.