An investigation was carried out in the years 2006-2008 in order to compare the chemical composition of sweet sorghum stems. Two varieties of sweet sorghum: Sucrosorgo G-1990 (photoperiodically sensitive – headless) and Sucrosorgo 506 (photoperiodically insensitive – headed) were tested. Samples of large and small diameter stems were collected from both types of sorghum, from different parts of stem (lower, medium and top internodes). Each internode was fractionated into three stem part: leaves, the outer (rind) and the inner part (pith). The effect of the part of a stem and the place from which internodes were collected on the chemical composition was determined. The content of crude fibre and its fractions: neutral detergent fibre (NDF), acid detergent fibre (ADF), hemicellulose, crude proteins, carbohydrates: total carbohydrates, sucrose, reducing sugars and macroelements was determined in the plant material. The largest diversity in proportions of the chemical compounds was observed in the pith. Amounts of the NDF fraction in the rind depended on a stem’s diameter. The site from where an internode sample was collected had the greatest effect on the chemical composition, mostly the concentrations of macroelements (N, P - in all three stem parts, K and Mg – in the pith, Ca - in leaves and the rind, Na - in leaves). The diameter of a stem had a negative effect on the chemical composition and deteriorated the technological value of sorghum, since the content of crude fibre and its fraction increased.

24.1.2019