Stem, Leaf, and Panicle Yield and Nutrient Content of Biomass and Sweet Sorghum

Abstract

Core Ideas Sorghum is a potential dedicated bioenergy crop both from biomass and sugar yields. Increasing rates of N fertilizer affected biomass yield and nutrient removal for sorghum cultivar ES5200 by partitioning resources primarily toward the stem component. For sorghum M81‐E, the seed head component accounted for a greater proportion of biomass, compared with sorghum ES5200, and biomass yield and nutrients were more evenly distributed among the three components. Returning the leaf and seed head components back to the field to enhance soil fertility has the potential to provide at least 45, 7, and, 26 kg ha−1 of N, P, and K, respectively. Information on biomass yield and nutrient content among leaf, stem, and head components can aid on sorghum [Sorghum bicolor (L.) Moench] cultivar selection and harvest management practices to optimize the quality of the harvested feedstock and residue management. The objectives of this study were to characterize and to determine the effect of five N fertilization rates (0, 67, 134, 201, and 268 kg ha−1) on biomass yield and N, P, and K content of the stem, leaf, and panicle components of two dedicated bioenergy sorghum cultivars. Biomass sorghum Blade ES5200 and sweet sorghum M81‐E were grown in 2014 and 2015 in North Carolina. For ES5200, total biomass yield was 14.4 Mg ha−1 with 74, 25, and 2% accounted by the stem, leaf, and panicle, respectively. For M81‐E, total biomass yield was 11.5 Mg ha−1 with 62, 24, and 15% accounted by the stem, leaf, and panicle, respectively. Nutrient content by the leaf + panicle components combined were about 45, 7, and 26 kg ha−1 for N, P, and K, respectively, for both cultivars; however, for ES5200, the leaf + panicle components combined accounted for 46, 37, and 16% of total N, P, and K content, respectively, whereas for M81‐E they accounted for 62, 74, and 24% of total N, P, and K content, respectively. Addition of N fertilizer resulted in greater shifts in the stem component responses but to different extents for each cultivar.