Journal of Energy Bioscience 2025, Vol.16, No.4, 193-204 http://bioscipublisher.com/index.php/jeb 194 2 Conceptual Framework of Energy Utilization Efficiency in Sorghum 2.1 Physiological basis Sorghum bicolor L. Is an energy crop. It has a high yield, is drought-tolerant and can adapt to poor soil. The energy utilization efficiency of sorghum is mainly influenced by photosynthetic efficiency, water use efficiency (WUE), nutrient absorption and transformation efficiency, etc. During the growing season, the photosynthetic productivity and WUE of sorghum are both relatively high. In arid or semi-arid regions, its WUE can reach 3.04 kg C mm⁻¹ H₂O, which is better than that of energy crops such as corn and miscanthus (Rinaldi, 2013; Garofalo and Enciso et al., 2019; Moore et al., 2021). The absorption and utilization efficiency of nitrogen also affects the biomass of sorghum and the theoretical ethanol yield. Moderate application of nitrogen can increase yield, but excessive application will reduce nitrogen utilization efficiency (Wiedenfeld, 1984). 2.2 Agronomic and environmental influences The energy utilization efficiency of sorghum is influenced by factors such as fertilization, farming methods, water management and climatic conditions. Research has found that with minimal tillage and no fertilization, energy efficiency is the highest (up to 18.68). High input (such as a large amount of chemical fertilizers) can increase output, but energy efficiency will decline instead. The combination of organic and inorganic fertilizers, straw returning to the field and other practices can not only increase yield, but also optimize energy efficiency (Lopez-Sandin et al., 2019; Pashynska, 2019; Jankowski et al., 2020). In terms of water management, moderately reducing irrigation can improve the efficiency of water and energy utilization while maintaining production, especially suitable for the Mediterranean and arid regions (Garofalo and Rinaldi, 2013; Enciso et al., 2019; Pietro Garofalo et al., 2025). Environmental factors such as precipitation, temperature and soil type can also affect the biomass accumulation and energy conversion efficiency of sorghum (Enciso et al., 2019; Jankowski et al., 2020; Bazaluk et al., 2021). 2.3 Measurement methods The energy utilization efficiency of sorghum is mainly measured by the following indicators: Energy efficiency (EE): The ratio of output energy to input energy, used to measure energy conversion efficiency (Jankowski et al., 2020; Bazaluk et al., 2021). Energy productivity (EP): The yield per unit of energy input (kg·MJ⁻¹), reflecting the economy (Lopez-Sandin et al., 2019). Specific energy consumption (SE): Energy required per unit of output (MJ·kg⁻¹), indicating the level of production consumption (Brito et al., 2017; Okoro and Isa, 2021; Perazzini et al., 2021). Net energy (NE): The difference between output energy and input energy, representing the surplus of the system (Jankowski et al., 2020). Water use efficiency (WUE): Biomass or energy produced per unit of water consumption (Garofalo and Rinaldi, 2013; Enciso et al., 2019; Moore et al., 2021). These data are derived from field experiments, energy input-output calculations, crop physiological measurements and mathematical model analyses, providing references for the evaluation and optimization of energy utilization efficiency of sorghum (Brito et al., 2017; Lopez-Sandin et al., 2019; Jankowski et al., 2020; Okoro and Isa, 2021; Perazzini et al., 2021). 3 Genetic Improvement Strategies 3.1 Breeding for high EUE traits High EUE breeding is mainly aimed at enabling sorghum to grow more and utilize resources more efficiently. The key points include increasing biomass, adjusting plant structure and improving nitrogen utilization efficiency. Breeders will take advantage of natural genetic differences to select varieties that remain high-yielding under low-nitrogen conditions (Bollam et al., 2021; Ostmeyer et al., 2022) (Figure 1). For instance, genetic differences
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