Bordus O. Introduction and agrotechnological aspects of paulownia cultivation under conditions of the Right-bank Forest Steppe of Ukraine

Main research results. The introduction presents the relevance of the topic of work, connection of work with scientific programs, topics, the purpose and objectives of research which was achieved by establishing the characteristics of plant growth and development and the biomass formation of paulownia energy plantations. Laws of distribution of aerial part of the plant are established. An effective method of introducing in vitro explants from sprouted seed into the plant has been developed. The first section presents the analyzed and stored results of the scientific works of Ukrainian and foreign scientists on cultivation for bioenergy, biological features of plant growth and development, and the formation of ground part depending on meteorological and agrotechnological measures. Based on the analysis of literary sources, a conclusion was made as the research was aimed at improving technologies for paulownia cultivation, but there is not too much information about the features. The second section describes the program, research methodology, soil and climatic conditions during the years of research. The third section presents the research results on multiplication of valuable cultivars of the genus Paulownia, the technology of introduction into in vitro culture, and the adaptation of cultural seedlings to ex vitro. It was established that the method of in vitro culture of sprouted seed with an apical meristem with germ layers are highly effective in sterilization efficiency in 20% sodium hypochlorite solution. It has been found that during cultivation on nutrient media with the use of phytohormones BAP (benzylaminopurine) and kinetin, plants generate additional shoots. The best results were on the nutrient medium with the inclusion of hormonal substances BAP 1.5 mg/l and kinetin 1.5 mg/l which significantly increases the yield of segments per explant in vitro and may reach up to 7.4 segments per plant. Adaptation of cultivated plantsto cultivation conditions іn ex vitro was conducted. Its success depended on the elements of technology, ensuring the axial growth of shoots with the addition of gibberellin 0.15 ml/l before transplanting into soil for rooting. The time period for transplanting is the summer months since June till July at high temperatures from 27 to 30 °С and the average survival rate may reach 94.7%. The fourth section describes the research results on establishing the elements of paulownia growing technology of two types such as paulownia felt (Paulownia tomentosa (Thunb.) Steud.) and cultivar “Clone in vitro 112'' as raw materials for the production of biofuel. Pursuant to result of the study agrobiological properties have been established. In order to ensure the processing industry with the production of biofuel as a raw material, it is necessary to increase industrial plantations of high-yielding tree crops among which the most productive crop is paulownia. According to the research results, it was established that the optimal density of paulownia plants on one hectare is 625 pieces/ha. According to the number of plants per unit area, paulownia plants grow up for 425 cm per the first year of ‘Clone in vitro 112’vegetation and respectively - 1020 cm in four years, and paulownia felt - 260 cm and 660 cm per 4 years respectively. For 5-6 years of vegetation, 1 hectare of paulownia plants can ensure 250-300 m3 of commercial wood and the same amount of 50% of biomass (twigs). Raw materials of paulownia, especially the axial shoot and branches, can be used for the production of fuel pellets and chips, which contain a low ash of 0.9-1.6%. Leaves and petioles of paulownia are with high content of ash (3.9-7.1%) due to an increase in the content of nutritions including nitrogen. In the fifth section, the peculiarities of growth, plant development and the formation of the chemical composition of paulownia biomass species in the zone of the Right-bank Forest Steppe of Ukraine and the biological properties of two types of paulownia such as ‘Clone in vitro 112’ and paulownia felt are determined. The main period of wood accumulation occurs in the first three years of vegetation with one of the highest indicators of biomass productivity. During five years of vegetation, one tree can be with mean increment of paulownia ‘Clone in vitro 112’approximately 0.35 m3 and 0.24 m3 for paulownia felt. The studies determined the nutrients content, the lack or excess of which has a particularly negative effect on the biomass quality. The main amount of nitrogen in the studied species of paulownia is concentrated in leaves (2.3–2.6%) and petioles (0.67–1.1%).