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Sorghum (Sorghum bicolor L.) is well‐known to adapt to stressful environmental conditions. However, yield variability of sorghum has not been thoroughly investigated for different growing conditions in a subtropical climate. The overall goal of this study was to identify yield potential and management options for sorghum production in the southeastern United States. Specific objectives were to calibrate and evaluate the Cropping System Model (CSM)–CERES–Sorghum model with sorghum variety trial data and to apply the model for determining hybrid performance as a function of sowing date for different environments in Georgia. The model was calibrated and evaluated with data for six grain sorghum hybrids from 31 variety trials conducted in Georgia and Florida. Following calibration and evaluation, the model was used to simulate grain yield of the six hybrids in response to seven sowing dates under rainfed and irrigated conditions at 10 locations in Georgia using 40 yr of historical weather data. The results indicate that normalized root mean square error (RMSEn) between simulated and observed yield for the six hybrids ranged from 1.4 to 19% for model calibration and from 12 to 28% for model evaluation, suggesting that the model can be calibrated and evaluated using limited data from variety trials. For the long‐term scenarios, differences in simulated grain yield were found for hybrids, sowing dates, and locations under both rainfed and irrigated conditions. This demonstrated that the CSM–CERES–Sorghum model can be used to investigate the effects of climate variability on crop yield and to develop management practices for optimizing sorghum production. Core Ideas: CSM–CERES–Sorghum model can be calibrated and evaluated using limited data from variety trials.Locations, hybrids, and sowing dates contributing to high sorghum yield can be identified.The model can be used to study climate variability impacts and develop management practices. [ABSTRACT FROM AUTHOR]

Perennial bioenergy grasses can potentially replace fossil fuels and offset atmospheric CO 2 through soil C sequestration. However, limited information relevant to the impacts of bioenergy cropping on ecosystem services, especially above- and below-ground productivity and soil C sequestration is available for subtropical environments (e.g., southeastern USA). The objective of this study was to evaluate the impacts of perennial bioenergy cropping on C cycling and accumulation in the soil following four years of production in North Florida. Treatments consisted of six perennial grass species: giant reed, elephantgrass, energycane, sugarcane, sweetcane, and giant miscanthus. Elephantgrass, energycane, sweetcane, and sugarcane produced great shoot biomass (31–41 Mg ha−1) when harvested once per year. Giant reed's shoot biomass responded favorably to two harvests per year (27–43 Mg ha−1), whereas giant miscanthus did not perform well in any of the years (9–21 Mg ha−1). Additionally, giant reed, sweetcane, and giant miscanthus produced greater root biomass (9–11 Mg ha−1) compared with the other three species (2.5–3.2 Mg ha−1). Among the six grasses, sweetcane, energycane, and elephantgrass resulted in increases in soil C stocks (~15 Mg ha−1) relative to the initial level. Conversely, giant reed and giant miscanthus had no increase in soil C stock. Results suggested that interspecies differences observed in biomass yield among the six perennial bioenergy grasses could therefore affect soil C accumulation. High biomass yielding species such as sweetcane, energycane, and elephantgrass can effectively increase soil C within a few years following establishment in a subtropical environment. • Giant reed, sweetcane, sugarcane, energycane, and elephantgrass were able to produce high shoot biomass in North Florida. • Giant miscanthus could not produce comparable shoot biomass with other species in the subtropical environment. • Sweetcane, energycane, and elephantgrass exhibited significant increases in soil C stock over four growing seasons. • Sweetcane, energycane, and elephantgrass are able to provide multiple ecosystem services rapidly following establishment. [ABSTRACT FROM AUTHOR]