EFFECTS OF DIFFERENT WATER STRESS LEVELS ON BIOMASS YIELD AND AGRONOMIC TRAITS OF SWITCHGRASS (Panicum virgatum L.) VARIETIES UNDER SEMI-ARID CONDITIONS

This experiment was conducted to determine the effects of different water stress levels on biomass yield, plant height, number of stalks per meter, single stalk weight, yield reduction ratios and irrigation water use efficiency (IWUE) values of switchgrass (Panicum virgatum L.) varieties under Central Anatolia conditions. The study was conducted for two years (2016 - 2017) in the Randomized Complete Block Design arranged in split plots with three replications under Konya ecological conditions. Six switchgrass varieties (Shelter, Alamo, Cave in rock, Shawnee, Kanlow and Trailblazer) and five different irrigation treatments (water stress levels: S1: Full irrigation; S2: 75% of full irrigation; S3: 50% of full irrigation; S4: 25% of full irrigation and S5: Rain-fed without irrigation) were used in this experiment. Kanlow, Alamo and Trailblazer varieties had greater biomass yields than the other varieties in all water stress treatments. Under different water stress treatments, dry biomass yields varied between 48300 kg ha(-1) (S5- Cave in rock) and 25120 kg ha-1 (S1- Kanlow); plant heights varied between 70 cm (S5) and 180 cm (S1); number of stalks per meter varied between 221 (S5) and 356 (S1); single stalk weights varied between 0.56 g (S5) and 2.25 g (S1). IWUE was calculated as 5.7 kg m-3 for the first harvest and as 2.1 kg m(-3) for the second harvest. Considering the biomass yields from single harvest of rain-fed treatments (S5) and two harvests of the other irrigation treatments (S1-S4), IWUE values and water deficits of the region, it was concluded that single harvest was more suitable for switchgrass plants grown under ecological conditions.