Double‐Cropping Sorghum for Biomass

Double‐cropping systems have been suggested as a way to increase annual dry matter production per hectare, while simultaneously delivering environmental benefits. Past research seems to indicate that there is a genotypic effect for the suitability of a crop for use within double‐cropping systems; however, despite sorghum's [ Sorghum bicolor (L.) Moench] diverse genetic background, there has not been a great deal of work done to explore this response for this crop. Twelve sorghum varieties were grown as sole crops and within a double‐cropping system with winter triticale [× Triticosecale Wittmack] in central and northern Iowa. Results showed that although the single‐cropping system produced slightly higher biomass yields, there were no significant differences in total production between the two systems for several of the sorghum varieties. These varieties were characterized as earlier maturing ones that had nearly maximized dry matter production at the time of harvest for the double‐cropping system, and thus, any potential loss in sorghum yield was supplemented by the biomass production from the triticale crop. However when the chemical composition of the crops was considered, the theoretical ethanol yield of the single‐cropping system was greater than the double‐cropping system for all sorghum varieties. Although triticale was capable of offsetting any potential loss in dry matter, as an ethanol feedstock it was inferior to sorghum.