Bondarenko P. Intensive sweet cherry orchard systems for the Southern Steppe of Ukraine

The dissertation presents research results on selection of elements of intensive sweet cherry orchard systems, namely clonal rootstocks and interstems, length of the interstem, planting schemes, which would contribute to increase of the yield, fruit quality and economic effect in non-irrigated conditions of the Southern Steppe of Ukraine. Trees with VSL-2 and Gisela 5 interstems exhibited greater vigour than the trees grafted on VSL-2 rootstock. At the same time, there was no significant difference in tree canopy projection area as the main indicator of the suitability of the rootstock to high density planting .Increasing the length of VSL-2 interstem to 30 cm reduced the tree vigour by 10-20%, to 50 cm – by 20-30% depending on vigour index, compared to the 20 cm interstem. Trees with interstems formed a 21-23% larger leaf surface area than those grafted on VSL-2 rootstock. The leaf area index of trees with interstems was also higher. Better light interception to the peripheral zones of tree canopies on Krupnoplidna cultivar was observed for 5 x 4 m planting scheme where it was on average 15% higher than for 5 x 3 m scheme. Planting schemes did not affect this index of the trees of Melitopolska chorna cultivar. Shadow leaves partially compensated for the lack of light by increasing the pigment content in the dry matter by 15-40% compared with the leaves in conditions of sufficient light. Net photosynthetic productivity of peripheral zones of the canopy was on average 1.8 times higher than in the central parts of the canopy. It was found that net photosynthetic productivity of central zones of the canopies of trees with interstems was 14-26% higher compared to trees grafted on VSL-2 rootstock, on canopy periphery – 8-10% higher. The highest density of sweet cherry spurs was observed on two and three year old wood – 14.1-20.2 and 12.2-18.9 spurs / m of branch respectively. Spur density decreased significantly with the increasing age of fruiting wood, with 13% of spurs preserved on seven year old wood. Trees using the VSL-2 and Gisela 5 interstems showed a 26% increase in the number of spurs on one tree and 8-12% increase in the number of flowers in generative bud compared to the trees grafted on VSL-2 rootstock. The degree of winter hardiness of the generative buds and fruit set were determined largely by the specific weather conditions of the year, especially spring frosts and genetic characteristics of the cultivars, and less – by the influence of the elements of the orchard systems. 2015 and 2018 were the most favourable years for trees of Valery Chkalov and Melitopolska chorna cultivars, while 2014 and 2015 – for Krupnoplidna cultivar. The yield of trees in Mahaleb / VSL-2 and Mahaleb / Gisela 5 combinations was on average 1.5 and 1.4 times respectively higher than then of trees grafted on VSL-2 rootstock. The specific yield per unit area of canopy projection and canopy volume of trees with interstems was also 30-41% higher. Mahaleb / Gisela 5 (5 x 3 m planting scheme) variant had the highest average yield for 2014-2018 period on Melitopolska chorna cultivar – 8.0 t / ha. Variants Mahaleb / VSL-2 (5 x 4 scheme) and Mahaleb / Gisela 5 (5 x 3 m scheme) had the highest average yield on Krupnoplidna cultivar – 6.3 and 6.9 t / ha, respectively. In years with favourable weather conditions, the yield of these types of plantations reached 12.0-12.9 t / ha. The use of 30 cm long VSL-2 interstem on Valery Chkalov and Melitopolska chorna cultivars allowed the orchards to reach yields of 9.0-10.1 t / ha in tenth-fourteenth leaf. The use of VSL-2 and Gisela 5 interstems contributed to the increase of mean fruit weight by 5-8% compared to the trees on VSL-2 rootstock. Increasing the length of VSL-2 interstem to 50 cm reduced mean fruit weight by 11% compared to 30 cm interstem length. Cultivar features had the greatest influence on most indices of biochemical composition of fruits (share of the factor influence – 51-81%). Sweet cherry cultivation technology in the research was economically effective. In Mahaleb / VSL-2 / Melitopolska chorna (5 x 3 m) orchard system, net profit amounted to 62 thousand UAH / ha, profitability – to 72%; for Mahaleb / Gisela 5 / Krupnoplidna (5 x 3 m) - 50 thousand UAH / ha and 64%, respectively. The use of VSL-2 interstem with 30 cm length allowed to obtain 74-86 thousand UAH / ha of net profit and achieve a profitability level of 78-84%. Based on the modelling method, it was determined that calibration of Krupnoplidna cultivar sweet cherry fruits by factions of diameter allows obtaining additional net profit of 8-23 thousand UAH / ha and to increase the profitability level by 14-35%.