• Energy Research

Purpose. Study of the dynamics of formation of biometric indicators, biomass yield and energy potential of sorghum varieties in the conditions of the Central ForestSteppe of Ukraine. Methods. Field, laboratory and statistical methods were used. Five registered varieties of sorghum, viz: ‘Huliver’, ‘Dovista’, ‘Zubr’, ‘Su’ and ‘Tsukrove’ served as the object of research. The measurement of biometric indicators of plants, the calculation of biomass yield and energy potential were carried out in accordance with approved scientific and methodological recommendations. Results. The most rapid growth in height of sorghum was observed during the interphases of “seedling – leaf-tube formation and leaf-tube formation – flowering”. At the end of the growing season, plants of the varieties ‘Huliver’ (237.2–245.1 cm), ‘Tsukrove’ (218.0–227.2 cm) and ‘Dovista’ (205.6–220.9 cm) were the tallest. ‘Hulliver’, ‘Tsukrove’ and ‘Zubr’ were characterized by the largest photosynthetic leaf area, they produced the largest biomass and were characterized by the highest energy efficiency of cultivation in terms of energy productivity (EPс equal to or greater than 60.0 GJ/ha) and energy efficiency coefficient (Kee equal to or greater than 4.0). Conclusions. The highest biomass yield by dry residue was found in the sorghum varieties ‘Huliver’ (15.4 t/ha), ‘Tsukrove’ (15.2 t/ha) and ‘Zubr’ (12.5 t/ha). The same varieties were characterized by high energy productivity (the difference between the energy stored in biomass and the energy used to produce it) – 65.3, 64.9 and 56.8 GJ/ha respectively, with a Kee value of 4.0 or more, which characterizes the average level of biomass production efficiency.

Today clearing of contaminated soils from heavy metals, pesticide residues is very important problem for Ukraine. Soil pollution is considered to be the result of the functioning of metallurgical and chemical industrial enterprises, as well as the irrational application of chemical plant protection means in the agricultural sector. The range of such preparations as well as the areas of contaminated soils are increasing every year. Phytoremediation with the help of herbaceous plants is one of the most effective methods of decontamination. This list of plants should be supplemented by perennial energy crops, taking into account the absorbing powers of their root system. The basis for preparing the material was the multiple scientific literary sources of domestic and foreign scientists on an investigated theme, the working-out of relevant techniques and scientific and practical recommendations. We applied both general scientific methods (dialectics, analysis and synthesis) and special ones for conducting of analytical review of literature. The largest area of soil in Ukraine is contaminated with cobalt, molybdenum, and copper, whose content exceeds not only the background values but also the maximum permissible concentrations (MPC). It has been defined that the intensity of heavy metals transition in the system “soil-plant” of the energy crops has the following form Cd→Cu→Zn→Pb. Perennial energy crops are capable to create quickly an above ground phytomass and to form an aggressive root system that enables them to accumulate heavy metals from the soil. They can be new and important plants for phytoremediation. At the same time, the energy crops are allocated in accordance with agroclimatic zoning taking into account plant responses to the growing conditions and also applying the scheme of soil remediation from heavy metals. It has been established that energy crops (Switchgrass and Silvergrass) are Hyperaccumulators. They actively absorb heavy metals and partialy accumulate them in their underground and above ground parts. Silvergrass (Miscanthus giganteus) provides higher yield than switchgrass (Panicum virgatum), though switchgrass has less dry matter content, higher accumulation of heavy metals in plant phytomass but the maximum permissible concentration is lower than regulated standards. Silvergrass (Miscanthus giganteus) provides higher yield than switchgrass (Panicum virgatum), though switchgrass has less dry matter content, higher accumulation of heavy metals in plant phytomass and maximum permissible concentration is lower than regulated standards. On termination of the vegetation, the above-ground vegetative mass of these plants can undergo to proper processing that is an additional source of non-ferrous metals or biofuel production for energy purposes.

Purpose. The study aimed to compare the efficiency of the resource-saving technology with the conventional technology for switchgrass cultivation using the developed methodology for assessing the economic and energy efficiency. Methodology / approach. The study used general and special methods, including the methodology of scientific research in agronomy, laboratory determination of dry matter content in biomass, quantitative-weight analysis to establish crop yield, and the authors’ improved methodology for assessing economic and energy efficiency. The research results were statistically processed using variance and comparative analysis. Results. The results of the research on the use of resource-saving cultivation technology in comparison with conventional technology show an increase in switchgrass biomass yield from 14.6 to 15.7 t/ha, an increase in economic efficiency with profitability growth from 73.8 to 79.0 %, and an increase in energy efficiency with a growth of the energy efficiency coefficient by 0.7 – from 4 to 4.7 (average level of energy efficiency) when applying a specific complex of agrotechnical measures. When using resource-saving technology, the average full cost of cultivating switchgrass for six years is 8305.6 UAH/ha, compared to 7952.8 UAH/ha with conventional technology. However, resource-saving technology generates an average sales revenue of 14867.5 UAH/t, which is 1045 UAH/t more than conventional technology (13822.5 UAH/t). Originality / scientific novelty. For the first time, a field experiment was conducted to compare switchgrass cultivation using resource-saving and conventional technologies. The authors have developed a methodology to assess the economic and energy efficiency of cultivating switchgrass. The results indicate that the efficiency of switchgrass biomass production is influenced by improved cultivation technology. The authors have developed a three-dimensional econometric model that demonstrates how the profitability level depends on the chosen switchgrass cultivation technology. Practical value / implications. The research results have practical significance as they have led to the development of a methodology and evaluate the economic and energy efficiency of switchgrass cultivation. These results will be useful for agrarian enterprises to save resources.