GENETICS AND MANAGEMENT OF PHYSIOLOGICAL SYSTEMS OF SORGHUM FOR BIOMASS PRODUCTION

Sorghum (Sorghum bicolor (L.) Moench) is one of the five most important cereal crops in the world. A wide range of types has been developed in studying grain, sweet, high energy, and biomass. The purpose of this paper was to describe the variability of traits and systems affecting biomass quantity and quality. Different maturities and heights between cultivars existed among test materials.' Maximum dry biomass yield was to 35.1 Mg ha(-1). Two harvest sequences of 120-60 or 90-90 days per season (original seeded crop plus a ratoon) were superior to other sequences. Total carbohydrate content of the biomass (less the panicle) ranged from 73 to 84%. Cultivars produced a range of 22.2 to 46.9% non-structural carbohydrates and 38.1 to 64.6% structural carbohydrates. Structural components varied for cellulose (35.0 to 19.8%), hemicellulose (28.9 to 19.9%), and lignin (6.9 to 3.3%). Two types of hemicellulose were identified in the cultivars tested. Results showed the highest percent of structural carbohydrates was localized in the culm rind. Stems and leaf blades were similar in levels of structural carbohydrates but stems were significantly higher in non-structural carbohydrates. An inverse relationship between non-structural carbohydrates and total structural components is present in biomass. Total volatile solid content of all types exceeded 92%, but genetic differences exist among cultivars. Percentage reduction of the volatile solids appeared different between cultivars. Amount of methane produced and biomass yield (quantity and quality) can be increased/decreased by management practices and genotypic selection.