THE INFLUENCE OF FERTILIZATION AND BIOPROTECTION SYSTEMS ON THE DEVELOPMENT OF ALTERNARIA BLIGHT AND YIELD OF POTATO VARIETY MYROSLAVA UNDER CONDITIONS OF THE SOUTHERN POLISSIA OF UKRAINE

The article presents the results of a three-year (2023–2025) field experiment investigating the complex impact of green manure, organic fertilization, differentiated application schedules of modern biostimulants, and microbiological fungicides on the phytosanitary state and productivity of potato (Solanum tuberosum L.) plantings. The research was conducted at the experimental base of the Institute of Potato Research of NAAN (Nemishaieve, Buchanskyi district, Kyiv region) on the mid-season variety Myroslava. Field trials were established in the Southern Polissia zone in a three-fold replication with a randomized plot design under the infectious pressure of Alternaria blight (Alternaria solani / Alternaria alternata). It was established that enhancing mineral and organic nutrition through the integration of green manure (white mustard + white mustard) and cattle manure at a dose of 40 t/ha serves as a powerful preventive measure. This practice independently reduced the development of early blight by 11.0 % and disease incidence by 18.0 %, which ensured a net yield increase of 5.3 t/ha (from 22.3 to 27.6 t/ha) compared to the pure green manure background. A statistically significant (LSD0.5 = 1.12 % for development); (LSD0.5 = 1.18 t/ha for yield) advantage of the multi-component biofungicide Mikohelp over the bacterial preparation Fitohelp was proved across both agrochemical backgrounds under their three-fold application scheme (soil application into holes during planting + two subsequent foliar sprays during vegetation). The maximum protective and economic effect was recorded when combining the organic-green manure background with a crop protection system that included the application of the VIT-ORG VG biostimulant and Mikohelp biofungicide during planting, followed by a double foliar spraying in a tank mix during the budding and mass flowering phases of potatoes. This scheme minimized the development of Alternaria blight in the Myroslava variety to 16.6 % (incidence – 29.6 %) and allowed obtaining a record average yield of 32.3 t/ha (maximum increase in the trial was +4.7 t/ha to the background control), which is 3.1 times lower in terms of damage level and 10.0 t/ha higher in productivity compared to the absolute control. High efficiency was also demonstrated by the combination of Biogran and Mikohelp (at planting) + StimPure AA (twice foliarly) + Mikohelp (twice foliarly during vegetation), where the average yield reached 31.8 t/ha on the organic-green manure background with a disease development of 16.9 %.