Impact of Harvest Timing and Hybrid Selection On Energy Sorghum Yields.

Successful development of a cellulosic biofuel industry requires a predictable and sustainable supply of biomass. Timely harvest and proper hybrid selection are essential to maximize yield and duration of biomass supply to bioenergy facilities. Four replications of five photoperiod sensitive single-cut biomass sorghum hybrids and six multi-cut energy sorghum hybrids were planted at two locations for up to three years to measure biomass accumulation. Biomass was measured bi-weekly until the end of the growing season for primary and ratoon growth. For multi-cut hybrids, primary harvest was initiated in June (early), July (mid), and August (late) to allow for ratoon harvest. Single-cut biomass sorghum dry matter yields were significantly greater (p<0.05) than multi-cut energy sorghums (primary + ratoon growth) averaged across all site-year combinations.  Timing of ratoon harvest did affect total dry matter yields of multi-cut systems. Early ratoon harvest reduced (p<0.05) dry matter yields of primary harvest for early compared to late ratoon systems and the extended period for regrowth did not compensate for reduced primary growth. Maximum dry matter yields were similar among single-cut hybrids. However, optimum yield was obtained up to 36 days sooner for two single-cut hybrids (SugarT and Top76-6) compared to the remaining three (ES5200, Es5201, SS405). Results of our study highlight the importance of timely harvest and hybrid selection to optimize yield and supply of biomass.