The application of reflective vegetation indices is crucial for advancing precision agriculture, particularly in monitoring crop growth and development. Among these indices, the Normalized Difference Vegetation Index (NDVI) is the most widely used due to its reliability in capturing vegetation dynamics. This study focuses on the applicability and temporal dynamics of the NDVI in monitoring winter wheat (Triticum aestivum) under the specific climatic conditions of Southern Dobrudja, Bulgaria. Using a Survey3W Camera RGN mounted on DJI unmanned aerial vehicles (Phantom 4 Pro and Mavic 2 Pro) at an altitude of 100 m, NDVI data were collected over a five-year period (2019–2024). Results reveal distinct NDVI trends, with maximum values reaching 0.56 during favorable conditions, and sharp declines during late spring frosts or drought periods. These NDVI variations correlate strongly with environmental factors, including precipitation and temperature fluctuations. For instance, during the 2019–2020 season, the NDVI decreased by 30% due to severe drought and high winter temperatures. In this study, vegetation indices, including the Soil-Adjusted Vegetation Index (SAVI) and the Enhanced Vegetation Index (EVI), were utilized to compare the results with the NDVI. The high-resolution UAV methodology demonstrated in this study proves highly effective for breeding and agronomic applications, offering precise data for optimizing wheat cultivation under variable agro-climatic conditions. These findings highlight the NDVI’s potential to enhance crop monitoring, yield prediction, and stress response management in winter wheat.

Chlorophyll content is directly related to the rate of photosynthesis. Changes in the photosynthesis due to reduced amount of chlorophyll affect the weight and quality of grain. A two-year field trial was carried out (2022-2023, 2023-2024) with 12 varieties and lines of common winter wheat with the aim to determine the relationship of chlorophyll concentration during grain filling with yield and its components. The index of chlorophyll content was determined using Chlorophyll Content Meter Model CCM-200 Plus. The measurements were done at stage grain filling, the accessions being grouped according to their date to heading. Chlorophyll content was most variable in the early heading genotypes. The results were unidirectional over years. During the first vegetative growth season, a significant positive correlation with yield was determined, while during the second vegetative growth season it was negative but low. A low correlation of chlorophyll concentration with test weight and protein content in grain was found. The established significant differences in the chlorophyll concentration between the individual genotypes confirmed the possibility of using this precise tool for differentiation of the lines during the breeding process. The identified genotypes with high chlorophyll content were suitable to use as potential germplasm in the breeding programs.

The long phenological development of the cereals determines the great variety of factors, which influence the vegetative growth and the formation of their productivity. A priority of the contemporary agricultural practices is the better balance between the agro ecological, biological and technological elements and the higher profitability of production, while limiting the unfavorable effects on the environment. In this relation, breeding is faced with the problem of developing cultivars which can efficiently utilize the nutrients from soil and at a later stage convert them into grain yield. The aim of this investigation was to determine the productivity structure of new genotypes and perspective lines of winter malting barley (Hordeum vulgare L.), developed at Agricultural Institute - Karnobat and Dobrudzha Agricultural Institute - General Toshevo, as well as the correlation between grain yield and its components. The investigation was carried out during cropping seasons 2014 – 2016, which were very different with regard to the combination of meteorological factors. All investigated components of the formed shoot mass, which contributed to the realization of the biological yield potential of the malting barley cultivars, were influenced by the meteorological conditions of the respective year, by the specificity of the cultivar and by their interaction. It was found that the year conditions had determining role for the formation of the biological potential of the leaves, stems, spike and grain. The cultivar had a dominant role for the formation of the number of spikes per ha, the total shoot mass, 1000 kernel weight, the weight of the non-grain part of the spike and its percent from the weight of spike, respectively the weight of grain. By the grain yield formed, all tested materials exceeded the standard Kaskadyor 3. The exceeding varied from 9.02 % in cultivar Yaspis to 52.58 % in line 1015-127. Cultivars Asparuh, Deviniya and Ahat also had high mean productivity, exceeding the standard with 47.56 %, 45. 56% and 41.41%, respectively. High positive correlations were found between grain yield and spike yield, GHI, weight of grain per spike, weight of 1000 grain, NGPS and total mass. The investigated winter malting barley cultivars, regardless of their breeding location, possess high productivity potential and are suitable for growing in the region of Dobrudzha.