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The Southern Steppe of Ukraine is characterised by a range of unfavourable agro-climatic conditions, which leads to inhibition of growth processes, disruption of physiological processes and loss of crop yields. The use of environmentally safe bioregulators stimulates growth processes, optimises nitrogen nutrition, increases the adaptability of legumes to adverse conditions and increases yields. The purpose of this study was to find out the specific features of the influence of biostimulants on the formation of the photoassimilation apparatus of pea of the Oplot variety in the Southern Steppe of Ukraine. A 3-year small-plot study was conducted to determine the leaf area index, total chlorophyll content, and net photosynthetic productivity in pea crops. The biostimulants were used for pre-sowing and foliar treatment of pea crops in the budding phase at concentrations described in the methodology. It was found that Stimpo (25 ml/t + 20 ml/ha) increased the leaf surface index in different stages of vegetation of pea variety Oplot by 1.12-1.54 times and Regoplant (250 ml/t + 50 ml/ha) increased the leaf surface index by 1.18-1.38 times compared to the control. A significant increase in the chlorophyll content in pea stipules was recorded after foliar treatment of crops with biostimulants and exceeded the value of control plants by 9.0-10.4% in the BBCH stages 61(65) – 75(79). Based on 3-year results, the positive impact of biostimulants on net photosynthetic productivity was proven. Thus, Stimpo and Regoplant increased the net photosynthetic productivity of pea crops by 35% and 22%, respectively, in the budding (BBCH 51-61) and flowering (BBCH 55-65) phases. The obtained scientific results contribute to the widespread use of the studied biostimulants in the technology of pea cultivation in the Southern Steppe zone of Ukraine to increase crop productivity and obtain a high-quality crop
Kolesnikov et al. (Sat,) studied this question.