Yield and Forage Value of a Dual-Purpose bmr-12 Sorghum Hybrid

Interest in grain sorghum [Sorghum bicolor (L.) Moench] has increased since 2012 when the United States Environmental Protection Agency (EPA) announced that sorghum grain qualifies as an advanced biofuel. In addition, sorghum is drought-tolerant, and using it as a biofeedstock does not substantially compete with food production. However, sorghum yields less than corn [Zea mays L.] under well-irrigated conditions. Value-added traits will be needed in sorghum to compete with corn and reduce water requirements for bioenergy crop production. We introduced the brown midrib-12 (bmr-12) mutation, associated with increased stover ethanol fermentation efficiency and digestibility by cattle, into the sorghum grain hybrid AWheatland × RTx430 (BMR) and tested its effectiveness as a dual-purpose (grain and biomass) crop relative to the near-isogenic wild-type (WT). Four replicated paddocks (2.3 ha) were planted in 2006 and 2008 near Mead, Nebraska. Crossbred yearling steers (239 ± 17 kg hd^-1) grazed (2.6 animal units ha^-1) paddocks following grain harvest for 61 to 72 d. Stover was sampled at 4, 30, and 60 d. BMR grain yield was 6% less (P = 0.01) than WT with no difference in stover NDF content, but BMR stover had higher in vitro NDF digestibility (7%; P < 0.001), steer average daily gain (0.17 kg hd^-1 d^-1; P = 0.001), and body weight gain (110 kg ha^-1; P = 0.002), resulting in an estimated increased net return of $131 ha^-1. Results suggest that this bmr-12 hybrid is an effective dual-purpose sorghum crop for both grain and biomass production.