Grain and biofuel production potential of sweet sorghum genotypes under variable fertilizer regimes in Ethiopian agroecologies

Abstract

In Ethiopia, sweet sorghum (<i>Sorghum bicolor</i> (L.) Moench) shows strong potential as a feedstock for ethanol production. However, a consistent supply of raw material remains a major constraint for sweet sorghum-based ethanol distilleries. To improve productivity, field experiments were carried out during the 2018–2019 growing seasons at Melkassa and Miesso (rainfed) and Werer (irrigated) to assess the performance of various sweet sorghum genotypes under two different fertilizer treatments. Agronomic and quality traits, including grain yield, panicle weight, plant height, and ethanol yield, varied significantly across genotypes, environments, and fertilizer treatments. Genotypes E36-1, ICSR93034, and IESV92207DL produced high sugar, ethanol, juice, and stalk yields, with IESV92207DL showing the highest grain yield. Genotypes such as ICSR93034, IS2331, and ICSB324 exhibited stable performance under both fertilizer levels, indicating their suitability for low-input systems. In contrast, genotypes like IESV92099DL and MR£22XIS8613/3/1/2/5-2-1 performed well with fertilizer but poorly without it. Fertilizer significantly enhanced growth, sugar accumulation, and yield components. Fertilizer application increased ethanol and sugar yields by 12.65%, while juice yield increased by 4.12% and dry stalk yield by 1.86%, showing differential trait responses. Grain yield showed a strong positive relationship with both panicle weight and panicle width, whereas ethanol yield, juice volume, sugar concentration, and fresh stalk biomass were also positively linked. These results emphasize sweet sorghum’s promise as a sustainable source of ethanol, with performance shaped by genotype, environmental conditions, and fertilizer application, highlighting the importance of improved agronomic practices.