Yatsenko V. Optimization of sunflower cultivation technology with the use of growth regulators under the conditions of the north-eastern Forest-Steppe of Ukraine

Sunflower is an important crop for Ukraine's economy, characterized by a high level of domestic processing of crops and a dominant influence on the formation of the world market. The range of soil-climatic and agrotechnical conditions of the northeastern Forest-Steppe of Ukraine, which is different from the main growing zone, causes a low level of manifestation of adaptive breeding traits formed in other environmental conditions. The range and mechanisms that provide a shift in the indicators of optimal crop density under the action of retardants depending on the variety, plant vegetation density and treatment scheme were determined. It was proved that the change of plant morphotype was accompanied by a right-hand shift of the optimal density range. Depending on the treatment scheme, the values of the optimal density index increased in the following direction: without treatment (k) -> treatment of vegetative plants -> seed treatment -> complex treatment. The values changed as follows: for the Esman variety from 67.5 under control to 85.3 thousand plants / ha in the variant with complex treatment; for the hybrid of Zlatson from 60.2 to 69.3-70.1 thousand plants / ha; for the Bozhedar hybrid from 58.1 on control to 67.5 thousand plants / ha; for the Patricia hybrid from 60.1 to 77.1 thousand plants / ha. It is determined that the estimated sowing density of the Horal hybrid for basic technologies is 55 thousand plants / ha. In order to maintain yield indicators in technologies using growth regulators, it is advisable to thicken the sowing to 70 thousand plants/ha. The range of technological regulation of plant height and leaf surface index of sunflower hybrid crops depending on density and type of growth regulators was established. According to the results of the field experiment, the possibility of technological reduction of stem height in commercial sunflower crops by 18.5-23.1 cm or 11.1-12.6% was confirmed. The influence of retardants on the change of optimal parameters of final density, structure of yield and crop productivity of sunflower hybrids was proved. It was found that the use of the Architect drug provided an increase in the value’s of 1000 seeds and the number of seeds per head. The maximum effect was observed in the variants with a density of 64.3 and 71.4 thousand plants / ha. It has been established on average, for varieties, the highest level of yield increase in the entire density range of + 0.23 t/ha was ensured by the use of the Architect drug. In terms of varieties, the Architect provided the highest yield: for the variety of Esman - 2.84 t / ha in areas with a density of 71.4 thousand plants / ha; for the Zlatson, Bozhedar and Patricia hybrids - 3.26; 3.42 and 3.75 t / ha, respectively, in areas with a density of 64.3 thousand plants / ha. With the use of Moddus 250 EC, an increase in yields was observed only for Zlatson, Bozhedar and Patricia hybrids in areas with a density of 71.4 thousand plants / ha. It was determined that the use of Moddus 250 EC and Architect drugs provided statistically significant increase in the average oil content in sunflower seeds from 47.63% (in control) to 48.65 and 48.48%, respectively.