Planting Date Affects Biomass and Brix of Sweet Sorghum Grown for Biofuel across Florida

Sweet sorghum [Sorghum bicolor (L.) Moench] is a potential bioenergy crop that is capable of high biomass and sugar yields, but production for biofuel in the Southeast is not well understood. The present study examined the effects of planting date (three dates from mid-March to mid-June) on primary and ratoon crop fresh biomass, brix, and estimated sugar yield of three sweet sorghum cultivars ('Dale', 'Topper 76-6', and 'M-81E') grown at three sites from North (29 degrees 24'N) to South Florida (26 degrees 40'N). Across all treatments, primary crop fresh biomass, brix and estimated sugar yields were 70 Mg ha(-1), 148 g kg(-1), and 5.69 Mg ha(-1), respectively. Primary crop yields were greatest for the two earliest planting dates (mid-March to mid-May), and for our southernmost site. The yield potential for ratoon crops was in general only about half as much as the primary crop across all years, sites, and cultivars for the earliest planting date. An exception, however, was ratoon crop yields at the southernmost site, which were in some cases equal to or greater than primary crop yields. Low primary crop brix values were found for all cultivars on the muck soils in South Florida compared to the other two sites, and for M-81E compared to Dale and Topper 76-6. These low brix values were correlated with greater fresh biomass production. Further research is needed on planting dates for optimizing primary and ratoon crop yields along with varietal development with improved ratoon crop yields.