Root lodging affects biomass yield and carbohydrate composition in sweet sorghum

Sweet sorghum [Sorghum bicolor (L.) Moench] is a promising crop for bioenergy production but is susceptible to lodging, which has the potential to significantly affect biomass composition and total harvestable yield. Despite known susceptibility to lodging, there are limited data available on the effects of root lodging on biomass and carbohydrate yield and partitioning in lodged sweet sorghum. Therefore, weather-induced lodging of field-grown sweet sorghum in 2012 and 2013 in North Central Florida was exploited to provide a better understanding of the effects of root lodging on biomass and carbohydrate yield and partitioning to leaf, stem, and panicle. Fresh biomass yields were not different between lodged and non-lodged plots in 2012 or 2013, but dry biomass yield was lower during 2012. Grain yield was lower during both years of the study, as a result of lodging. However, no difference in leaf or stem biomass yield was seen due to lodging. Lodging reduced biomass recovered by flail harvester at harvest by 40% during 2012. Juice Brix showed a 32 and 17% decline in lodged compared to non-lodged sorghum at harvest during 2012 and 2013, respectively. Total nonstructural carbohydrates (starch and water soluble carbohydrates) showed a 27% reduction on a whole plant basis as a result of lodging during 2013, with panicles showing a greater percent reduction (53 vs. 18%) in total nonstructural carbohydrates (mostly starch) as a result of lodging compared with stems (mostly water soluble carbohydrates). Although sweet sorghum is susceptible to root lodging in many environments, it is likely to have only a relatively modest effect on water-soluble carbohydrates in the stem.