AGROMETEOROLOGICAL CONDITIONS AND DYNAMICS OF VEGETATION INDICES OF WINTER WHEAT IN THE SOUTHERN STEPPE OF UKRAINE
Abstract
To comprehensively assess the agrometeorological conditions of the 2021–2025 growing seasons for winter wheat in the Southern Steppe of Ukraine and to identify the patterns of NDVI, NDRE, and NDMI vegetation index dynamics under seasonal variations in temperature, precipitation, and water deficit. Methods. The study was conducted at the Educational, Scientific and Practical Center of Mykolaiv National Agrarian University. Meteorological data from the Pessl Instruments (iMETOS) automatic weather station for 2021–2025 and Sentinel‑2 SR Harmonized satellite imagery processed in the Google Earth Engine environment were used. NDVI, NDRE, and NDMI were calculated to assess crop conditions, and their dynamics were comparatively analyzed in relation to air temperature, precipitation, and the main phenological growth stages of winter wheat. Results. Significant interannual differences in agrometeorological conditions were found to determine the formation and seasonal dynamics of vegetation indices. The 2021–2022 and 2022–2023 growing seasons were the most favorable for crop development, with NDVI reaching 0.8–0.9 and NDRE 0.6–0.7. The 2023–2024 season was characterized by suppressed autumn growth followed by compensatory biomass accumulation in spring, whereas the favorable autumn conditions of 2024–2025 did not ensure prolonged spring development because of a cold and relatively dry spring. June was identified as the most critical period for the development of water stress during the transition from heading to grain filling. NDMI responded earliest to deterioration of crop water status and proved to be the most sensitive indicator of water stress, whereas the shortening of the NDVI plateau indicated limitations in the realization of the crop productivity potential. Conclusions. The dynamics of winter wheat vegetation indices are closely associated with seasonal temperature and moisture conditions. Spring weather conditions played a decisive role in determining crop physiological status, while the transition from heading to grain filling was the most critical period for water stress development. NDMI is recommended as an early indicator of crop water stress, whereas the combined use of NDVI, NDRE, and NDMI provides effective crop monitoring, and the shortening of the NDVI plateau may serve as an indicator of limitations in the realization of winter wheat productivity potential.
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