Photosynthetic parameters of sugar beet crops under application of measures to increase tolerance to drought stress in the Right Bank Forest Steppe of Ukraine

Abstract

Purpose. To establish the peculiarities of the photosynthetic parameters of sugar beet crops under the application of measures to increase the crop tolerance to drought stress in the zone of unstable soil moisture of the Right Bank Forest Steppe of Ukraine. Methods. The research was carried out at the experimental field of the Institute of Bioenergy Crops and Sugar Beet of the National Academy of Agrarian ciences of Ukraine (50.023194, 30.173895) in 2014–2018. The research scheme included the application of the moisture retainer Aquasorb (300 kg/ha), soil treatment with the Mirazonit soil bacteria concentrate (20 kg/ha), application of the plant growth regulator Kelpak RK (2 l/ha, BBCH 14 + 4 l/ha, BBCH 18) and microfertilizers Alpha-Grow-Extra Buriaky (3 l/ha, BBCH 18) and Micro-Mineralis (Buriaky) (1.5 l/ha, BBCH 18) during vegetation season. Aquasorb moisture retainer was applied to the soil during early spring cultivation using an Amazone ZA-TS 3200 spreader. Results. During the vegetation period of sugar beets, specifically in the 6-leaf stages (BBCH 16), closing of leaves in rows (BBCH 30) and between rows (BBCH 39) and in the period of technical ripeness (BBCH 49) we studied the peculiarities of the formation of indicators of the assimilation apparatus area and the content of photosynthetic pigments (chlorophylls a and b) in the leaves,in the corresponding interphase periods, we studied the photosynthetic potential of crops and the net productivity of photosynthesis under the influence of the studied factors. It was established that in the phase of leaf closure between rows (BBCH 39), sugar beet plants formed an assimilation surface area of 54.1 thousand m2/ha, the difference between the hydrogel application options and the control was 3.5 thousand m2/ha. Also, the best indicators of the formation of the leaf area were provided by the variants of the combined combination of all elements of the experiment – 56.36–56.47 thousand m2/ha, which, most likely, was caused by their influence on the physiological state of plants and, as a result, on the formation of a somewhat larger assimilation apparatus. In the period of closing of leaves in rows – closing of leaves between inter-rows (BBCH 30–39), the options for using the Aquasorb moisture retainer had a more intense accumulation of dry matter by an average of 0.9 g/m2 per day. At the same time, as the main root grew and the root system developed the deeper layers of the soil, the sugar beet plants became more and more independent of the influence of applied agrotechnical measures. This is especially evident when comparing the Aquasorb application options, which on average had a more intensive accumulation of dry matter by 0.2 g/m2 per day in the interphase period of leaf closure in the between rows – technical ripeness (BBCH 39–49). Conclusions. The use of agrotechnical measures is an effective factor in intensifying the photosynthetic activity of sugar beet plants throughout the growing season, the effectiveness of which is largely determined by their combination options. In general, the most optimal conditions for the formation of photosynthetic parameters of crops were provided by combination of all factors of the experiment.