Horbatiuk E. The Formation of Sunflower Hybrids Productivity Depending on the Sowing Terms and Row Spacing in the Conditions of the Steppe of Ukraine

The dissertation work presents the results of researches on features of growth, development and formation of a sunflower crop, depending on the elements of cultivation technology, namely the hybrid, sowing term and row spacing. There are established the peculiarities of the sowing photosynthetic potential formation process, the dry matter accumulation, the root system development of sunflower hybrids due to the influence of weather conditions of the region, also, there is substantiated sowing dates and row spacing influence on the yield level and seeds quality. There are presented the calculating results of the economic and bioenergy efficiency of sunflower growing depending on the factors investigated. The dissertation is devoted to the establishment and to the scientific substantiation of biological and technological peculiarities of the formation of sunflower hybrids productivity for the influence of sowing dates and seed width in the conditions of the Steppe of Ukraine. Depending on hybrid, sowing term and row spacing yield capacity figures changed within the limits of 1.84–3.10 t/hа. The most adverse weather conditions of 2014 provided yield formation on the level of 1.5–2.75 t/hа. The PR64F50, PR64A15 and Jason hybrids received the highest yield capacity figures for their sowing within the recommended sowing terms (by heating the soil to a depth of 10 сm at 10–12 ºС) and by sowing with the row spacing of 35 сm. These figures were: PR64F50 hybrid 2.58 t/hа, PR64A15 hybrid – 2.7 t/hа, Jason hybrid – 2.38 t/hа. Reaction of the PR64A89 and Forward hybrids to the factors under study was rather different. They formed top yield capacity within the early sowing term (by reaching the soil temperature to a depth of 10 сm at 6–8 ºС) the row spacing of 45 сm with the figures: the PR64A89 hybrid – 2.57 t/hа and the Forward hybrid – 2.43 t/hа. Calculation results of the involvement of the factors in the yield formation show that yield capacity of the sunflower hybrids under study is mostly defined by the factor «Row spacing» – 31 %. Such factors as «Weather conditions» – 24 %, «Hybrid» – 21 % and «Sowing terms» – 18 % had significant impact.