Daniela Avetisyan1 and Galya Cvetanova2
1 Bulgarian Academy of Sciences, Space Research and Technology Institute, Department of Aerospace Information, Sofia 1113, Bulgaria
2 Agricultural Academy, Agriculture Experimental Station, Lom 3600, Bulgaria
Avetisyan, D. & Cvetanova, G. (2022). Assessment of drought impact on phenological development of selected sunflower hybrids based on vegetation indices and orthogonalization of multispectral satellite data. Bulg. J. Agric. Sci., 28 (6), 1006–1026
Agriculture is one of the leading sectors, directly affected by the negative impacts of climate change and in particular of drought. Water stress is amongst the key growth limiting factors in crop production. It is expected that in the next decades Bulgaria will be affected by warming of air temperatures and reduction of precipitation sum that will significantly increase the risk of droughts. Although, sunflower (Helianthus annuus L.) is known to be a drought tolerant crop, sufficient and optimized agrotechnical activities are needed to achieve yield increase under changing environmental conditions and depletion of natural resources. The proper irrigation scheduling, for example, requires determination of biologically optimal health and water status for different sunflower varieties, at different stages of ontogeny. The research suggests a remote sensing methodology, integrating vegetation indices and orthogonalization of multispectral satellite data for studying phenological development of selected sunflower hybrids under drought conditions. Two indices – Normalized Differential Greenness Index (NDGI), and Normalized Differential Wetness Index (NDWNI), based on Tasseled Cap Transformation are introduced for agricultural assessments. The results show the dynamics of water and health status of the studied agroecosystems in the different growth stages, defined according to BBCH scale. NDGI and NDWNI appear to be especially suitable for determination of timing and duration of growth stages and for monitoring of the status of the studied crops during these stages. The methodology possesses a great potential for better understanding of drought impact on crop dynamics and functioning.