The study aimed to evaluate the genetic diversity of 41 sweet sorghum genotypes from seven countries for key biofuel-related traits over two sorghum growing seasons (2020 and 2021) in a semi-arid Mediterranean environment. Genotypes were assessed for key bioethanol production traits such as fresh stalk yield (FSY), juice yield (JY), Brix, dry biomass yield (DBY), theoretical juice ethanol yield (JEY), theoretical lignocellulosic ethanol yield (LEY), theoretical total ethanol yield (TEY), as well as their potential for solid biofuel production, measured through bagasse ash, nitrogen, and moisture content. Significant variations were observed among genotypes across most traits, analyzed using analysis of variance, principal component analysis, and hierarchical cluster analysis, identifying DBY, LEY, and TEY as the primary contributors to overall genetic variation. Cluster analysis grouped the genotypes into five distinct clusters, highlighting the diversity in biofuel-related traits. The correlation analysis revealed significant positive relationships between traits such as FSY, DBY, and TEY, indicating that higher biomass production directly enhances ethanol output. Strong positive correlations between FSY and TEY underscore the importance of biomass yield in maximizing ethanol production. However, traits like bagasse ash and nitrogen contents, which were negatively correlated with JEY, LEY, and TEY, present challenges in improving biomass combustion quality. The study concludes that certain genotypes, particularly ‘Yellow Bonnet’ and ‘IS 3556’, exhibited strong potential for biofuel production in semi-arid Mediterranean climates where water scarcity and high temperature favor genotypes with high biomass and sugar yields. These genotypes demonstrated high JEYs, LEYs, and TEYs, suggesting their adaptability to the unique environmental stresses of this region, making them good candidates for sustainable biofuel production in similar climates.

Sweet sorghum seems to be one of the most promising energy crops for a wide range of ecological conditions thanks to its high yield potential and drought tolerance. A two-year field trial was conducted in a semi-arid Mediterranean environment in Turkey to evaluate the interactive effects of different nitrogen fertilizer levels (100, 150, and 200 kg ha⁻¹) and humic substances (0, 15, 30, and 45 L ha⁻¹) applications on the biomass and bioethanol yields of sweet sorghum, and combustion characteristics of its bagasse. Sweet sorghum showed a positive response to increased nitrogen fertilizer and humic subtances application levels in terms of biomass and bioethanol production. Lignocellulosic and total bioethanol yields significantly increased up to 2910 and 3336.6 L ha⁻¹ as a result of the combined application of the 200 kg ha⁻¹ N and 15 L ha⁻¹ humic subtances (HS), respectively. However, HS application had a detrimental effect on the bagasse combustion quality, because it caused a considerable increase in the mineral and ash concentrations. Briefly, combined application of 200 kg ha⁻¹ N and 15 L ha⁻¹ HS may be suggested to be applied for the sustainable bioethanol production from sweet sorghum, while the application of HS likely does not provide any economic and environmental benefit if bagasse would be used as solid biofuel feedstock.

The use of organic materials as a source of nutrients on agricultural lands ameliorates soil physical properties as well as being an environmentally friendly way of disposing of their wastes. This study was conducted to determine effects of three organic materials (poultry litter, cattle manure, leonardite) on yield and nutrient uptake of silage maize. Poultry litter and cattle manure were applied based on phosphorus (P) or nitrogen (N) requirements of the crop whereas leonardite was applied only one dose (500 kg ha⁻¹) and also combined with three inorganic fertilizer doses (100%, 75%, 50% of recommended inorganic fertilizer dose). According to the results, the highest green herbage yield and nutrient uptake values were observed in LEO-100 whereas N-based treatments significantly decreased yield and nutrient uptake of silage maize. The use of organic materials as a combination with inorganic fertilizer in silage maize cultivation is highly beneficial for sustainable forage production.