The dissertation work of Kalynov O.O. is dedicated to the topical problem of increasing sunflower productivity in the conditions of the Eastern Forest-Steppe of Ukraine by optimizing the plant nutrition system and stimulating plant growth using modern biological preparations. The relevance of the research is due to the insufficient level of realization of the biological potential of the sunflower crop in Ukraine, despite the positive dynamics of yield increase. One of the reasons for this is the insufficient use of soil potential, an unbalanced nutrition system, and the impact of abiotic stresses.The aim of the research was the theoretical substantiation and experimental study of the influence of various options of pre-sowing seed treatment and foliar fertilization using bacterial, mycorrhizal, and growth-stimulating preparations on the growth, development, productivity, and seed quality of the high-oil, early-ripening hybrid sunflower Aurora AM in the conditions of the Eastern Forest-Steppe of Ukraine.The research was conducted over three years, which allowed for a comprehensive assessment of the impact of the applied preparations under different weather conditions. The work used a complex of field, laboratory, and statistical research methods to obtain objective results.The dissertation abstract emphasizes that one of the promising directions for increasing sunflower yield is the use of growth stimulants, mycorrhizal and bacterial preparations. These biological agents are capable of improving plant nutrition through more effective involvement of soil nutrients, fixation of atmospheric nitrogen, increasing resistance to stress factors, and improving the overall condition of plants.
During the research, it was established that pre-sowing seed treatment contributed to an increase in field germination. The most statistically significant increase in germination was observed when seeds were treated with Mycofrend preparations, a mixture of Mycofrend with "PMK-U," and a mixture of Mycofrend, "PMK-U," and Black Jack.Due to improved field germination and plant survival, a higher plant density before harvesting was noted in the variants with seed treatment. The highest plant density before harvesting (47.4 thousand units/ha) was recorded in the variant of seed treatment with a mixture of all studied preparations in combination with foliar fertilizations, which exceeded the control by 5.6%.The studies showed that pre-sowing seed treatment with preparations based on humic substances, mycorrhizal fungi, and bacteria created better conditions for plant growth and development at the initial stages, which led to the prolongation of individual growth phases and the vegetation period as a whole. Foliar fertilizations also positively influenced plant development by improving nutrition and mitigating abiotic stresses.
The highest indicators of leaf area and leaf area index of sunflower crops at different development phases were observed in the variant of combining pre-sowing seed treatment with a mixture of Mycofrend, Black Jack, and "PMK-U" with three foliar fertilizations with a mixture of Black Jack with complex fertilizers Jiva MIX. In this variant, the leaf area index during the 61st and 80th microphases was significantly higher compared to the control.
The total photosynthetic potential (FPP) and FPP for individual growth phases were also highest in the variant combining pre-sowing seed treatment with three preparations and three foliar fertilizations. The increase in total FPP in this variant was almost 15.0% compared to the control. It should be noted that weather conditions significantly influenced the FPP indicators during the study years.Analysis of the yield structure elements showed that the highest indicators of head diameter, number of seeds per head, and their mass were achieved in the variant combining pre-sowing seed treatment with a mixture of Mycofrend, Black Jack, and "PMK-U" with three foliar fertilizations. The number of seeds per head in this variant was 11.4% higher, flower pollination completeness was 6.1% higher, and the mass of seeds per head was 14.0% higher compared to the control.The research confirmed that the influence of the studied factors on the biological yield of sunflower seeds was more pronounced than on the seed productivity of a single plant. Optimization of pre-sowing seed treatment and application of fertilizations contributed to both an increase in the mass of seeds from the head and the preservation of a larger number of plants until harvest.The highest biological yield of sunflower seeds (2.82 t/ha, which is 21.6% higher than the control) was recorded in the variant combining pre-sowing seed treatment with a mixture of all studied preparations and three foliar fertilizations. At the same time, there was no significant difference in yield between the variants with two and three fertilizations.
