Biomass yield and water-use efficiency in photoperiod-sensitive sorghum genotypes in the US Southern Great Plains

Photoperiod-sensitive (PS) sorghum [Sorghum bicolor (L.) Moench] has been developed as a bioenergy crop. However, little is known about PS sorghum production in semiarid environments. The objective of this study was to investigate water use, biomass yield, and water-use efficiency (WUE) in recently developed PS sorghum genotypes. Field experiments were conducted in 2 years and two locations in the US Southern Great Plains. Six genotypes (TAM08001, TAM17500, TAM17600, TAM17650, TAM17800, and TAM18000) were grown in three water regimes (dryland, irrigation at 50% evapotranspiration (ET) demand, and irrigation at 100% ET demand). For both locations, soil water extraction (SWE) occurred at a 0–2.4 m profile in 2018 but at a 0–1.2 m profile in 2019. At Bushland, TX, biomass yield ranged from 4 to 31 Mg ha⁻¹ and seasonal ET ranged from 251 to 743 mm. In contrast, variations of biomass yield (10–19 Mg ha⁻¹) and seasonal ET (345–483 mm) were smaller at Colby, KS. The WUE in PS sorghum (3.19–4.09 kg m⁻³) did not differ among water regimes except for the dryland treatment (1.52 kg m⁻³) at Bushland (2018). The genotypic differences in SWE, biomass yield, ET, and WUE were more pronounced under dryland conditions. TAM08001, TAM17800, and TAM17600 had greater biomass yield and WUE under drought conditions. Overall, biomass yield levels of 10–17 Mg ha⁻¹ can be achieved in dryland in western KS, but under irrigation at 50% ET demand in the TX High Plains. Further studies are needed to better understand shoot and root traits related to drought tolerance in PS sorghum.