Non-structural carbohydrates and fibre components in sweet and fibre sorghum as affected by low and normal input techniques

Since sorghum could be considered a multipurpose crop, the evaluation of the effects of agrotechniques on qualitative parameters is important to chose the most suitable destination. Two agrotechniques (low and normal input), two sorghum genotypes (sweet and fibre) and two plant populations (10 and 20 plants m(-2)) were compared in a factorial design with four replications in North Italy (44degrees33'N, 11degrees21'E, 32 m a.s.l) over the 3 years 1997-1999. Normal input increased biomass yield (11%) and dry leaves (16%) only of sweet sorghum. In 1999 normal input determined 30% more above ground dry matter and 18% more dry stems compared to the low input technique. Genotypes employed had a very different performance. On average panicles represented 2 and 28% of the whole dry matter of sweet (Keller) and fibre (H128) genotypes, respectively. Input level and plant density did never influence fibre chemical composition. Cellulose and hemicellulose content of stem were significantly lower in 1999 and they were negatively correlated with stem yield. Growing conditions never influenced lignin and its average content was 5.4% on stem dry matter. The higher stem yield in 1999 compared to 1998 may explain the higher cellulose and hemicellulose production in 1999 (+32 and +38%, respectively). Higher plant density was associated to the higher content of sucrose and lower content of glucose and fructose. Year and input level did not influence sucrose content of stem that on average was 31%. The clearly higher sucrose yield of 1999 (57 and 73% more than 1997 and 1998, respectively) was due to the higher stem yields. (C) 2004 Elsevier B.V. All rights reserved.