Biomass production, water and nitrogen use efficiency in photoperiod-sensitive sorghum in the Texas High Plains

Photoperiod-sensitive sorghum (Sorghum bicolor L. Moench) (PSS) has been identified as a potential bioenergy crop. However, little information is available for water and nitrogen (N) management in PSS in the Texas High Plains. The objectives of this study were to optimize water and N management for improving biomass yield, and to maximize water and N use efficiency in PSS. Two field experiments were conducted at different N rates (experiment I) and irrigation levels (experiment II). In experiment I, biomass yield ranged from 12 Mg ha−1 to 18 Mg ha−1 in two years. The optimum N rate and N use efficiency (NUE) were 183 kg ha−1 and 78 kg kg−1 in 2010, and 148 kg ha−1 and 90 kg kg−1 in 2011. In experiment II, biomass yield and evapotranspiration (ET) increased with increasing irrigation, but water use efficiency (WUE) was not affected by irrigation. ET was about 500 mm at full irrigation, 360 mm at limited irrigation, and 240 mm under dryland. Biomass yield ranged from 15 Mg ha−1 to 23 Mg ha−1, from 11 Mg ha−1 to 18 Mg ha−1, and from 8 Mg ha−1 to 13 Mg ha−1 at full and limited irrigation, and under dryland, respectively. WUE ranged from 30 kg ha−1 mm−1 to 47 kg ha−1 mm−1. Biomass yield and WUE varied among years but ET was relatively stable, suggesting higher WUE was due to increased biomass rather than reduced ET. The results of this study indicated PSS may achieve high biomass yield under limited irrigation.