Peculiarities of growth and development of sugar beets under the application of measures to increase tolerance to drought stress in the Right Bank Forest Steppe of Ukraine

Abstract

Purpose. To establish the patterns of sugar beet growth and development under application of measures to increase the crop tolerance to drought stress in the zone of unstable moisture of the Right Bank Forest Steppe of Ukraine. Methods. The research was carried out in the experimental field of the Institute of Bioenergy Crops and Sugar Beet of the National Academy of Agrarian Sciences of Ukraine (50.023194, 30.173895) during 2014–2018. The research scheme included the soil application of the moisture retaining agent Aquasorb (300 kg/ha), Mirazonit soil bacteria concentrate (20 kg/ha), application of the plant growth regulator Kelpak SC (2 l/ha, BBCH 14 + 4 l/ha, BBCH 18) and microfertilizers Alpha-Grow-Extra Beet (3 l/ha, BBCH 18) and Micro-Mineralis Beet (1.5 l/ha, BBCH 18). Aquasorb was applied during early spring tillage with the Amazone ZA-TS 3200 spreader. The soil was treated with the Mirazonit soil bacteria concentrate (20 l/ha) prior to cultivation using an Amazone UF field mounted sprayer at a flow rate of 200 l/ha. Results. Aquasorb moisture retaining agent at the application rate of 300 kg/ha ensured additional 5 mm of soil water in the soil layer of 0–20 cm, which is extremely important at the beginning of the vegetation season. In addition, hydrogel particles located close to the soil surface increase the soil water absorption capacity during rainfalls. Combined action of Aquasorb and Mirazonit ensured the most optimal indicators of plant density at the end of the vegetation season (108–109.3 thousand plants/ha). Most probably, this could be explained by the high efficiency of this biopreparation against the seedling borer. In particular, with an average prevalence of this pest in the 2.73% of the sowings, only 1.4–1.7% of sugar beet plants were damaged due to the complex action of hydrogel and Mirazonit. The use of plant growth regulator Kelpak SC had a positive effect on the formation of the length of lateral roots in the phase of leaf closure in the row (BBCH 30). In the phase of leaf closure between rows (BBCH 39) under the application of Aquasorb, the plants had 18.8 mm longer lateral roots, which ultimately ensured the formation of a higher root mass by 11.9 g/plant. At the same time, the effect of growth regulator on the length of the roots, both separately and in combination with other agricultural measures, was not detected. Conclusions. The best conditions for the growth and development of sugar beet plants were created in the treatment with the combined application of all studied agrotechnical practices. The practical significance of the obtained results lies in the improvement of crop cultivation technology in the zone of unstable soil moisture of the Right Bank Forest Steppe of Ukraine based on the comprehensive application of measures that contribute to increasing the crop tolerance to drought stress.